Palaeozoic tetrapods

Neck Wars, flightlessness in azhdarchids and more filling of Romer's Gap: SVPCA 2010

tetrapodzoology — Mon, 20 Sep 2010 08:56:01 +0000

Neck Wars, flightlessness in azhdarchids and more filling of Romer's Gap: SVPCA 2010

I said I wouldn't do any conferences this year. But I lied, and have recently returned from the 58th Symposium on Vertebrate Palaeontology and Comparative Anatomy (SVPCA), this year held once again in Cambridge, UK. Compared to the enormous, sprawling SVP (= Society of Vertebrate Paleontology) meeting with its numerous concurrent sessions (last year held in England, but usually held in North America), SVPCA is tiny and tidy. So, ok, there's less content, but at least you get to talk to everyone you want to, and to go to all the talks. As usual, I had an excellent time and extend warm thanks to the friends and colleagues who made it both fun and interesting.

Here, then, are just a few comments on some of the personal highlights. I'll go through them in approximate chronological order (as in: Palaeozoic, Mesozoic, Cenozoic). First of all, it goes without saying that we spent a lot of time at the University of Cambridge's Museum of Zoology. It's outstanding, housing hundreds of skeletons and preserved specimens of everything from caecilians and lungfishes to indricotheres, giraffes and beaked whales. I took a lot of photos, one or two of which are shown here [Mirounga leonina shown below... wow]. Anyway, to business...

Tim Smithson and Stan Wood discussed an assemblage of new small stem-tetrapods discovered in sediments dated to the Tournaisian, and hence to the infamous 'Romer's Gap' (a latest Devonian-early Carboniferous span of time, (mostly*) mysteriously devoid of tetrapod** fossils). Evidence for terrestrial arthropods was found in the same deposits. The discovery casts doubt on the hypothesis that terrestrial tetrapods and arthropods didn't exist in Romer's Gap due to low atmospheric oxygen content (Ward et al. 2006).

* But not entirely. See Clack (2002) and Warren (2007).

** The term Tetrapoda is used by some authors for the crown-clade that includes all extant tetrapods (and all descendants of their most recent common ancestor). If this is followed, the limbed sarcopterygians outside crown-Tetrapoda are termed either tetrapodomorphs or stem-tetrapods. Tetrapod in the phylogenetic sense is not necessarily, therefore, synonymous with tetrapod in the morphological sense.

Neck Wars!

Sauropods were comparatively well represented at the meeting with something like seven talks. Four of these were on neck posture and evolution, prompting John Hutchinson (the session chair) to refer to Neck Wars. Two talks were a direct response to the paper Mike P. Taylor, Mathew Wedel and I published last year (Taylor et al. 2009). Awesome: this is how science works [one of the figures from Taylor et al. (2009) is shown here. X-ray data shows elevated necks and neck bases in squamates, crocodilians and turtles: not just in mammals and birds].

In the first of those talks, John Martin looked at neck posture in extant animals. He aimed to show that some living animals do indeed adopt poses resembling those that emerge from osteological neutral pose (ONP). He therefore argued that ONP might really be a useful guide to 'habitual pose' or 'characteristic pose' (as in, the pose an animal is often seen to adopt). But I don't agree, for two reasons. (1) 'Habitual pose' as used by Taylor et al. (2009) and preceding authors means alert pose (the pose an animal adopts when unrestrained, awake, and unengaged in any particular behaviour), not feeding pose, or running pose, or anything like that. Even if sauropods did hold their necks low or horizontally when feeding or drinking (something that everyone thinks they did), it does not follow that their 'habitual pose' was also low or horizontal. (2) John used photos of numerous museum-mounted skeletons to demonstrate that ONP replicates life posture. But mounted skeletons (which are posed with their necks held at the same angle as those of living animals) do not depict life posture at all (you need x-rays to determine this: remember that actual neck skeleton posture is more elevated than the soft tissues seem to imply), nor are they in ONP! The last point was well made in Taylor et al. (2009): when you plug vertebrae together to reproduce ONP, you do NOT get 'habitual pose'.

In a related talk, Kent Stevens took issue with various of the statements made in Taylor et al. (2009), and used new (and excellent) CG models to depict possible neck postures and ranges of motion. He still regards sauropod neck pose to be more horizontal than we do, and his models permit less range of motion between the vertebrae than we consider likely. One of Kent's points was that - even with a near-horizontal neck - a sauropod like Apatosaurus is still capable of reaching upward somewhat by bending the front part of its neck up above the height of its shoulders. But the possibility of an elevated neck base still seemed disallowed, and this is an obvious point of contention. Kent says that sauropods preserved with such neck bases are in death poses and exhibit extreme opisthotonic postures, whereas other people refer to evidence indicating that such postures were definitely 'habitual' in life. We made a point of showing (Taylor et al. 2009) that elevated neck bases are present in squamates, testudines, crocodilians* and neognathous birds (not just ostriches!!), so Kent's implication that we only used rodents, rabbits and cats was a bit misleading.

* And we didn't get x-ray data on the most erect-necked of crocs.

Andreas Christiansen and Gordon Dzemski used neck biomechanics in an effort to analyse neck posture and concluded that erect neck postures were likely for Euhelopus and brachiosaurids. In fact, they found that - when resources were far apart - maintaining the neck in an erect pose was more efficient in term of energy expenditure than were other postures. Andreas also noted that the anatomy and range of movement present in sauropod necks makes low habitual postures unlikely, and he was amusingly critical of the Stevens & Parrish (1999) horizontal-necked hypothesis (as shown in Andreas's cartoon, used above).

To prove that we're all still friends and get along fine, we all went to dinner together, though the ensuing discussion ended in a brawl after Mike made an offensive comment (see adjacent photo, kindly taken by Adam Smith). Further thoughts on the Neck Wars can be seen here on SV-POW!

Mike P. Taylor examined necks as well, but he was more interested in working out why sauropods have been so good at evolving tremendously long necks while other terrestrial tetrapods have never been able to get beyond a 'glass ceiling' of c. 3 m. Pneumaticity, quadrupedalism, reduced reliance on oral processing and other factors combined to allow the evolution of extreme necks in sauropods: the absence of some or all of these factors have seemingly prevented giraffes and other non-sauropods from becoming quite so ridiculous.

OK, gotta stop there. More in part II!

For more on sauropod necks, see...

Refs - -

Clack, J. A. 2002. An early tetrapod from 'Romer's Gap'. Nature 418, 72-76.

Stevens KA, & Parrish JM (1999). Neck posture and feeding habits of two jurassic sauropod dinosaurs Science (New York, N.Y.), 284 (5415), 798-800 PMID: 10221910

Taylor, M. P., Wedel, M. J. & Naish, D. 2009. Head and neck posture in sauropod dinosaurs inferred from extant animals. Acta Palaeontologica Polonica 54, 213-220.

Ward, P., Labandeira, C., Laurin, M. & Berner, R. A. 2006. Confirmation of Romer's Gap as a low oxygen interval constraining the timing of initial arthropod and vertebrate terrestrialization. Proceedings of the National Academy of Sciences 103, 16818-16822.

Warren, A. 2007. New data on Ossinodus pueri, a stem tetrapod from the Early Carboniferous of Australia. Journal of Vertebrate Paleontology 27, 850-862.

tetrapodzoology Mon, 09/20/2010 - 04:56

Tags

Mesozoic dinosaurs

Palaeozoic tetrapods

There was a traveling dinosaur exhibit at the San Diego Natural History Museum (by the AMNH). They had a 'skeleton' of the 'Parrish et al' model of a sauropod. Next to it was 2 cervcials of a small Apatosaurus. They had them disarticulated. What impressed me was the size of the ball and socket, it was huge. To me this would mean they were very mobile. Not that does anything for the debate of neck posture, but the neck to me was very mobile and could turn/raise greatly.

an assemblage of new small stem-tetrapods discovered in sediments dated to the Tournaisian

Complete critters? Scrappy bits? New and novel stuff? Inquiring minds wish to know more.

You tantalized me with the mentioning of Romer's Gap in the title and hooked me into reading the blog post, but then left me starving with the meager tidbits you gave on this new material. :(

Speaking as a plant ecologist, I'm still trying to get my head around the environment that these sauropods were maneuvering those enormous necks and tails in. This makes moving a grant piano into an upstairs Victorian flat look trivial.

I'd suggest that the appropriate study, is to rent two boom lifts (those four-wheeled devices with an extendable boom on one end, with driver in the basket up top), secure them end to end, and try driving them through various landscapes, from dense forests to open fields. For real participatory science, have noted anatomists at the front end dodging branches and driving the whole rig. Two boom lifts are needed so that the front can be the neck emulator, and the back can be the tail emulator.

Just on first principles, I'd expect huge long necks to be extremely flexible, both to feed and to move. However, a high posture only works if there are few or no trees around to walk through.

AnJaCo and Nick: sorry to be so disappointing. Originally my article included a link to the abstracts themselves, but this got moved to part II when I split the article in two. The fossils themselves weren't fantastic - I only recall three incomplete jugals, all small (compared to taxa such as Acanthostega) and evidently representing distinct taxa. Some other material seemed to represent two additional taxa, similar in size to Pederpes. The abstract is here, but for the full story I guess we have to Wait For The Paper.

Heteromeles: sauropods were around for tens of millions of years and lived worldwide, so making generalisations about their habitat choice is not easy. Many better known forms (like the Morrison Formation taxa) apparently did inhabit open, parkland-type habitats. I'm not sure we can be confident that any species actually lived in dense forests. But they probably did, and you're right that neck and tail flexibility would be required for this to be possible. However, any conclusions we make about range of motion and flexibility is likely going to come from elsewhere.

I am not a paleontologist, but as an outside observer I am always disappointed by the way people talk about sauropods. They were unique in so many ways - size, growth rates, neck length, tiny heads - and still everybody seems to think of them as of some giant aberrant iguanas. To me it is obvious that their uniqueness can only be explained by unique lifestyle, that we are missing some critically important parts of the picture and can't think out of the box. Did they feed on some abundant fleshy food that didn't require chewing? Some fruit that didn't get preserved in the fossil record because it was so soft and tender? Mushrooms, may be? Or may be something really crazy, like sucking in algae-filled pond water, filtering it through some structure in the stomach and spitting it out? Also, did they use their necks to produce infrasound? There has to be something that nobody's considering.

Hey, what about flightless azdarchids? You promised them in this article's title. I demand flightless azhdarchids :D!!

Darren:

Mike P. Taylor examined necks as well, but he was more interested in working out why sauropods have been so good at evolving tremendously long necks while other terrestrial tetrapods have never been able to get beyond a 'glass ceiling' of c. 3 m. Pneumaticity, quadrupedalism, reduced reliance on oral processing and other factors combined to allow the evolution of extreme necks in sauropods: the absence of some or all of these factors have seemingly prevented giraffes and other non-sauropods from becoming quite so ridiculous.

Eh? Am I missing something, or is that some kind of goal-post-shifting way of saying that the giraffe doesn't really have a long neck? To me, it seems a bit offhanded (and, frankly, unfair) to suggest that, from an evolutionary point of view, absolute neck length is something more interesting and/or important than relative neck length.

Regarding the 'Why have sauropods been so good at evolving tremendously long necks' question: Correct me if I'm wrong, but the extra-long neck only evolved once during sauropod evolution, and those Jurassic and Cretaceous sauropods that we all know and love have evolved from ancestors that already had long necks, right? Thus, shouldn't the question rather be why virtually all sauropod lineages retained that long neck?

Vladimir (comment 6): sauropods are indeed a puzzle, but it's not as if palaeontologists aren't interested in, or talking about, these problem areas. Suggestions that they fed on carrion, bivalves, or soft waterplants, or that they filtered small animals from water have all been made, but all are speculative and contradicted by the extensive macro- and microwear typically present on sauropod teeth. This tooth wear (see, for example, Fiorillo 1991, Barrett & Upchurch 1994, 1995, Upchurch & Barrett 2000) shows that sauropods fed on relatively coarse plants, including conifers and ferns, though where they fed within the available vertical range remains contentious.

As for sauropod necks and infrasound, the possibility that sauropods used their super-long tracheae to produce infrasound has indeed been considered (informally) quite a bit: I've discussed it at length with someone who works on emu infrasound, and if you look at the comments appended to this article on bird tracheae you'll see many mentions of sauropod necks. I know of one discussion of sauropod infrasonic capabilities in the technical literature, but the publication concerned was only an abstract.

Frank (comment 7): flightlessness in azhdarchids coming next. As I said, all the SVPCA stuff was originally in one article but I then decided to cut it in two when it became too long.

Dartian (comment 8): I'll leave Mike to elaborate (he was, of course, being facetious), but even the biggest giraffe necks are short compared to typical sauropod necks. It's true that (so far as we know) the long sauropod neck evolved only once (and this must have been outside of Sauropoda, as sauropods are hardly the only long-necked sauropodomorphs). However, comparatively short necks evolved at least twice within Sauropoda (in dicraeosaurids and rebbachisaurids).

Refs - -

Barrett, P. M. & Upchurch, P. 1994. Feeding mechanisms of Diplodocus. Gaia 10, 195-203.

- . & Upchurch, P. 1995. Sauropod feeding mechanisms: their bearing on palaeoecology. In Sun, A. & Wang, Y. (eds) Sixth Symposium on Mesozoic Terrestrial Ecosystems and Biota, Short Papers. China Ocean Press (Beijing), pp. 107-110.

Fiorillo, A. R. 1991. Dental microwear on the teeth of Camarasaurus and Diplodocus: implications for sauropod palaeoecology. In Kielan-Jaworowska, Z., Heintz, N. & Nakrem, H. A. (eds) Fifth Symposium on Mesozoic Terrestrial Ecosystems and Biota, Extended Abstracts. Contributions from the Paleontological Museum, University of Oslo, 364, 23-24.

Upchurch, P. & Barrett, P. M. 2000. The evolution of sauropod feeding mechanisms. In Sues, H.-D. (ed) Evolution of Herbivory in Terrestrial Vertebrates: Perspectives from the Fossil Record. Cambridge University Press (Cambridge), pp. 79-122.

Dartian wrote:

Eh? Am I missing something, or is that some kind of goal-post-shifting way of saying that the giraffe doesn't really have a long neck? To me, it seems a bit offhanded (and, frankly, unfair) to suggest that, from an evolutionary point of view, absolute neck length is something more interesting and/or important than relative neck length.

Sauropods also absolutely annihilated giraffes in terms of neck:torso length ratio. If you don't believe me, compare for example the Omeisaurus skeleton at http://svpow.wordpress.com/2008/08/28/omeisaurus-is-just-plain-wrong/ with any of the many giraffe skeletons you can find in Google Images.

Still, just in case it wasn't obvious to you, I suppose I should explicitly state that the title of my talk was not really intended so much as criticism of giraffes as praise of sauropods. (The full title, as revealed in the second slide, was "Why giraffes have such short necks ... and how sauropods got it right".

Correct me if I'm wrong, but the extra-long neck only evolved once during sauropod evolution, and those Jurassic and Cretaceous sauropods that we all know and love have evolved from ancestors that already had long necks, right?

You're wrong :-) Ancestral sauropods had longISH necks, yes -- up there with those of giraffes -- but super-long necks (i.e. four times as long as that of the world-record giraffe) evolved in at least four widely separated sauropod linages: mamenchisaurs, diplodocids, brachiosaurids and titanosaurs. What I tried to bring out in my talk was that the anatomical prerequisites (pneumatic system, large size, distinctive vertebral anatomy, etc.) must have evolved in basal eusauropods, if not before, but that different lineages carried these features forward in very different ways.

Darren:

even the biggest giraffe necks are short compared to typical sauropod necks

Granted, but given the difference in body size between giraffe and sauropods, isn't that pretty trivial? I mean, everything is relative; for example, an adult Triceratops probably had, in absolute terms, a longer neck than the largest swan or the largest flamingo. But how informative would it be to refer to ceratopsians as 'long-necked' animals, and to swans and flamingos, respectively, as 'short-necked'?

Mike:

Sauropods also absolutely annihilated giraffes in terms of neck:torso length ratio.

Is that true for sauropods in general, or only for the most extremely long-necked taxa? Are there any quantitative studies on this?

the title of my talk was not really intended so much as criticism of giraffes as praise of sauropods

I was perhaps a bit too hasty in rushing to the defence of my fellow mammals. I'd like to point out, however, that over at SV-POW, you do tend to refer to 'stinkin' mammals'...

Tim Smithson and Stan Wood discussed an assemblage of new small stem-tetrapods discovered in sediments dated to the Tournaisian

And you can't spill any details beyond the abstract? :-( I'd be particularly interested to know if there are temno- and/or lepospondyls in there.

But thanks for alerting me to this in the first place. Last year at the SVP meeting, there was a talk by Anderson et al. on Tournaisian sites from eastern North America and the pretty wide variety of limbed vertebrates in them (basically, everything except temno- or lepospondyls, plus trackways by a small terrestrial animal), and Smithson had another on his new ?whatcheeriid of the same age. There won't be such talks this year, except if Wood has one (haven't searched the program for his name yet).

However, a high posture only works if there are few or no trees around to walk through.

A vertical stiff neck would work a lot better in a dense forest than a horizontal stiff neck.

David: so far as I recall, Smithson didn't proffer any possible identifications for the several taxa represented (and I couldn't tell you whether the figured jugals looked specifically like those of temnospondyls or lepospondyls, or indeed whatcheeriids or anything else). He did allude to the material from eastern North America that you refer to.

Re: sauropods and forests: The neck of adult Brachiosaurus looks thick enough to push away rather big branches.

Today rainforests are made impenetrable mostly by angiosperm lianas/creepers, but they have not yet evolved in Jurassic? Are there abundant fossils of Jurassic creepers eg. ferns?

Side question - similar plant-related question could be made about tapejarids and oviraptorids. Tapejarids are often interpreted as toucan or hornbill-like, but I never heard about fleshy fruits from Cretaceous. Oviraptorids are sometimes reconstructed as parrot-like seed crushes, but were there any hard seeds back then?

@Vladimir
One sauropod puzzle is how hatchlings grew to adult size within few years. They had the rate of growth comparable only to whales. But whales eat high-energy krill and fed their young on high-energy milk, and sauropods are supposed to eat low-energy coarse plants.

I suspect sauropods cared and fed their young somehow - by some means which left no trace in skeletons. Maybe they regurgitated food like birds, or evolved a different method altogether.

Darren: Thank you for the answer. I just can't see how such a huge amount of coarse conifer branches could be pushed through such a long narrow tube. What if tooth wear has nothing to do with the actual food item? Brown bear teeth sometimes show wear from shrub branches, but this wear happens as bears "filter" berries from branches, or bite off and crush Japanese stone pine cones to get seeds. Even now there's plenty of conifers with fleshy fruit - yews, podocarps, cycads - though almost nobody specializes on eating them nowadays. It is reasonable to assume that in absence of birds, trees relied on dinosaurs for seed dispersal, and produced fruit of sufficient size and nutritional value. But finding (and recognizing as such) a big fleshy fruit in the fossil record would be difficult.

I've read somewhere that dung beetles didn't feed on dung until Angiosperms became widespread, so it looks like there wasn't much around. If sauropods munched on conifer branches, they would have to produce quite a lot.

Jerzy - The whale model of sauropod growth has since been discounted (Erickson et al 2001, Lehman & Woodward 2008). Sauropods took a lot longer to reach adult size than whales (around 40-80 years), though sexual maturity would have happened earlier than that (probably around 20-25 years).

Erickson, G.M., K. C. Rogers, and S.A. Yerby. 2001. Dinosaurian Growth Patterns and Rapid Avian Growth Rates. Nature 412: 429-433.

Lehman, T.M., and Woodward, H.N. 2008. Modeling Growth Rates for Sauropod Dinosaurs. Paleobiology. Vol. 34(2): 264-281.

Since you're on the topic of Sauropod neck and other oddities I also have a question that floats in the back of my head everytime I see a picture of them. Just how efficient could their breathing have been. Their trachea was a mightly long breathing tube, and no matter how large the lungs, I'm just not altogether sure it was all that practical a setup. As a teenager I once tried out an experiment on that by trying to breath through about a meter-long hose. It wasn't long before I started feeling quite dizzy. I can't picture anything living 24-7 under such conditions. Did sauropods have air sacks? (once again not a scientist here, just a layman) Did they make that big a difference in breathing efficiency? What's the current wisdom on the topic?

Jura, did Lehman and Woodward demonstrate that Sander (2000) was in error when he plotted the life history of a Janenschia individual (fig. 10) based on growth lines, showing its attainment of sexual maturity after 11 years and full adult size at 26?

(Yes, that's a slower than whales; but still constitutes putting on mass as quickly as anything alive on land today.)

Mike - Lehman and Woodward did use Sander's work with Janenschia as it was (and may still be) considered to preserve the most complete record of growth for any sauropod. Sander didn't give any weight, or growth curve estimates in his paper, but the data they did provide was enough for Lehman and Woodward to extrapolate an adult mass of around 7 tonnes. Their results matched up pretty well with Sander's results (estimated age at adult: 20-30 years), and agreed well with Sander and Tuckmantel 2003 (age at adult of 19-35 years).

It is still an impressive growth rate. I think a comparison to whales is kinda misleading anyway. Whale babies receive all their nutrition from their mother, and they get an aqueous medium to hold their bodyweight. This frees up a lot of resources that can be directed strictly to growth. Sauropods had none of these options, and yet were still able to pack on the pounds at a pretty impressive rate. If anything, I'd say whale growth is anomalous.

Mike P. Taylor wrote:

"You're wrong :-) Ancestral sauropods had longISH necks, yes -- up there with those of giraffes -- but super-long necks (i.e. four times as long as that of the world-record giraffe) evolved in at least four widely separated sauropod linages: mamenchisaurs, diplodocids, brachiosaurids and titanosaurs."

This seems irrelevant. The determination of neck-elongation evolution is relative to the ancestors of the group in question, NOT an unrelated taxon. In this case, pre-sauropod sauropodomorphans, like melanorosaurs and anchisaurs (for example), have necks only slightly longer than their dorsal series, which must be related to the lineage that follows; if this lineage shows the trend to elongation, which is further elaborated in further clades from which shorter necks are known in ancestral forms, then and only then can one argue that "long necks evolved more than once in sauropods" (paraphrased). It seems instead that long necks evolved ONCE in sauropodomorphans, increased in length in basal Eusauropoda, and then multiple clades further increased this length. What you imply is that "long neck" refers only to the super-long necks of the four clades in question, but NOT to taxa like Shunosaurus lii or Cetiosaurus oxoniensis.

So, are the photos at the top just random snaps from the Cambridge Museum, or do they represent taxa that were talked about at the meeting? I'd love to here the latest news about Indricotheres(*) and Desmostylians(**)!
(*)Top right. There is a very similar skull on display at the AMNH in New York: is Paracerabaluchindrico known from two well-preserved skulls, or is one of these a cast of the other?
(**)Top center. I have moderately confident guesses about the (Genus-level) identity of three of the others, but the one at bottom center is some sort of Sauropsid, and I don't know them as well.

Allen:

Desmostylians(**) [...] (**)Top center

Isn't that the skeleton of an aardvark?

What must have evolved in that common ancestor of sauropodomorphs was a full complement of neck hearts. After that, insanely long necks were easy, even if not always necessary.

What good is a long neck? Wrap it around and around a tree, like a snake, and then LIFT to expose tasty roots.

>>Sauropods took a lot longer to reach adult size than whales (around 40-80 years),

How long did they *live* then???

>>Lehman and Woodward did use Sander's work with Janenschia as it was (and may still be) considered to preserve the most complete record of growth for any sauropod.

So then how did they go from 26 years to 40-80? Because Janenschia was pretty small as sauropods go?

So many things to respond to, so little time.

-- Mesozoic fruit (comment 14): from about the middle of the Cretaceous onwards, fruits are fairly abundant, though they are mostly small and berry-like. We don't know how heavily they were exploited by pterosaurs or dinosaurs, though gut contents and coprolites show that at least some ornithischians were eating them. As for the impenetrability of rainforests, remember that most sauropods were animals of open, parkland-type habitats, conifer-dominated woodlands etc.

-- Valagos (comment 18): sauropods (and other saurischian dinosaurs, and pterosaurs, and perhaps some other archosaurs) had pneumatised post-cranial bones. Use the search box (put in 'pneumaticity') or go over to SV-POW!

-- Sauropod growth rates: the relatively slow rates proposed by Lehman & Woodward may be erroneous - I heard that they incorporated a computational error, though I don't know if a correction for this has yet been published. Data from other specimens/studies indicates that giant sauropods took about 30 yrs to reach full size. Some of this was covered on Tet Zoo before: see the many comments attached to this pterosaur article.

-- Allen (comment 22): the skeletons are, indeed, just a random assortment of some of the ones on display. Dartian is right about the aardvark, sorry. And I'm pretty sure that the Paraceratherium skull is a replica of the AMNH one. Desmostylians will get some coverage in the next article.

What must have evolved in that common ancestor of sauropodomorphs was a full complement of neck hearts.

Arteries are already contractile; the only innovation that seems necessary is valves in the carotid arteries (valves already exist in many veins, and their number and distribution is subject to individual variation in humans).

After that, insanely long necks were easy

Only because of the air-sac system which made breathing through such a neck possible.

What good is a long neck? Wrap it around and around a tree, like a snake, and then LIFT to expose tasty roots.

Completely impossible for sauropods -- their necks were way too stiff for that.

In Saurischians, were very long necks somehow linked to development of herbivory, or at least some degree of "non-hypercarnivory"? Prosauropods had slender necks, and evolved to herbivores; Therizinosaurs, Oviraptorosaurs and ornithomimosaurs too. Hypercarnivores usually had bulky heads with shorter snouts (the "carnosaur" type).

Although I oversimplified with the few years, more like 10-25 years, but sauropod growth is still impressive.

Am I right that no modern animal achieves growth rate of sauropods on a diet of plants? Elephants are born at least 10 times heavier than hatching sauropods and are fed on milk for several years.

It's worth considering not just how sauropods may have managed to move in a tree filled environment, but how they might have affected such an environment. Elephants have a heavy impact on their environment, including vegetation patterns, and they are quite a bit smaller than most sauropods. If nothing else, game trails in the mesozoic must have resembled roadways, not narrow paths.

Darren (re #26)-- thanks for the Desmostylian news in the next post! While I cringe with shame about mis-identifying the skeleton in the top center of your top photo: I should have looked harder and thought about the implications of the long and heavy tail!

Mirounga leonina reminds me of that "walking seal" virtual reconstruction (Puijila darwini). Just the low stance, I suppose.

I don't know about other countries, but in Canada if a conference has a single stream, you can count it as an educational event and include the fee in your tuition tax deduction; if it has multiple streams so no one knows what you're attending, you can't. It might be worthwhile to look up the educational status if you can deduct professional memberships and tuition.

Is the vagus nerve loop a constraint on neck growth, e.g. in giraffes? Is it a constraint across all tetrapods, and did sauropods somehow solve it?

Is the vagus nerve loop a constraint on neck growth, e.g. in giraffes? Is it a constraint across all tetrapods, and did sauropods somehow solve it?

It's probably not a constraint, because the nerve fibers elongate as the neck develops. There are no a priori reasons to expect that they would hit a limit. All tetrapods have recurrent laryngeal nerves, even long-necked things like giraffes and ostriches, so the null hypothesis would certainly be that they were present in sauropods.

I'm happy to say that if you want more than that on the topic, please see my forthcoming paper (not for a few more months, unfortunately).

I'd like to point out, however, that over at SV-POW, you do tend to refer to 'stinkin' mammals'...

Considering the extent to which so many mammals use scent signals, often rather repellant to us humans, I think "stinkin' mammals" is a fair cop.

And they're not that discriminatory, because some SV-POW! posts are also labelled "stinkin' heads".

Further temnospondyl adventures: it's mostly about the dissorophoids (or some of them anyway)

tetrapodzoology — Wed, 30 Sep 2009 06:35:00 +0000

Further temnospondyl adventures: it's mostly about the dissorophoids (or some of them anyway)

First of all, here are some temnospondyls. This composite image was compiled by repositioning the reconstructions provided by DeFauw (1989): looks neat, doesn't it?

So, I recently returned from the 69th Society of Vertebrate Paleontology meeting, this year held in Bristol, UK: in other words, OUTSIDE OF NORTH AMERICA for the first time ever. It was combined with another meeting I normally attend, SVPCA (Symposium on Vertebrate Palaeontology and Comparative Anatomy), but I think that people sometimes forgot about this. The meeting was enormous and the sheer quantity of talks and posters, and people to meet and catch up with, was overwhelming. By necessity, sessions ran in parallel and - because I generally attended Mesozoic-, archosaur- and squamate-themed sessions - I missed everything on non-amniotes and synapsids. Together with Mike P. Taylor and Matt Wedel, I presented the poster 'Extant animals provide new insights on head and neck posture in sauropods' (oh, you mean you can get 'old insights' too?). It went down a storm and people seemed to like it [below: me with the poster. I don't have a good pic showing all three SV-POWsketeers posing with the poster, unfortunately]. More on it later, either here or at SV-POW! (which is soon approaching its second birthday by the way). Anyway, I'd like to discuss SVP stuff but I can't, so here's something completely different.

One of the people I met for the first time at the meeting was the legendary David MarjanoviÄ. One thing led to another, and here we are, back with the temnospondyls. I wrote this text in 2007 and was planning to complete the entire series before Tet Zoo-ing it. In the end, I've decided to publish and be damned, and to post the bits that look 'complete enough'. Have made a few attempts to incorporate two additional years of references, but please do tell me if I've missed anything and I'll then update the text. For the background and intro stuff you'll need to see Temnospondyls the early years (part I) and Temnospondyls the early years (part II), both of which were recently tinkered with and added to Palaeos [here and here], with my permission) .

Euskelians vs limnarchians

'Higher' temnospondyls (by which I mean those temnospondyls other than the edopoids and so on discussed in my previous articles) fall into two major clades, and in a large analysis of temnospondyl affinities published in 2000 Adam Yates and A. Anne Warren formerly named these Euskelia and Limnarchia. Euskelia means something like 'well limbed' and refers to the fact that members of this group typically possess well ossified limb bones that sport prominent crests and processes for muscle attachment (Euskelia was phylogenetically defined (Yates & Warren 2000, p. 85) as the stem-based clade that includes all those taxa closer to Eryops than to Parotosuchus*) [in adjacent image, the well ossified Eryops forelimb on the right represents Euskelia, while the poorly ossified Mastodonsaurus forelimb on the left represents Limnarchia. Image from Schoch (1999)]. Limnarchia means 'marsh ruler': the name refers both to the longevity of this clade (it is unique in making it into the Jurassic and Cretaceous) and the aquatic adaptations present in many of its members. Limnarchia was phylogenetically defined as the stem-based clade that includes all taxa closer to Parotosuchus than to Eryops (Yates & Warren 2000, p. 87). More recent phylogenies (see supertrees in Ruta et al. 2003, 2007), while supporting the division of 'higher' temnospondyls into Euskelia and Limnarchia, have found some of the clades thought by Yates & Warren (2000) to belong to Limnarchia (notably Dvinosauria) to fall outside of the Euskelia-Limnarchia clade [image below shows Ruta et al.'s (2007) temnospondyl supertree. You can't see all the names of course, but just look how many clades there are in this major radiation].

* A capitosaurian stereospondyl. Stereospondyli is a large and diverse mostly Mesozoic limnarchian temnospondyl clade.

Euskelians can be united on the basis of their broad postparietal bones, by the presence of a distinct articular surface for the radius on the humerus, and by many other characters: as a rough generalization, they were terrestrial animals with robust limbs. As always there were exceptions, and some members of the clade were aquatic. Yates & Warren (2000) found Euskelia to consist of two clades: Dissorophoidea and Eryopoidea. In this article we're going to look at just a few of the dissorophoids: the remaining dissorophoids, and the eryopoids, will be looked at later. There really are that many temnospondyls: it's shocking (I thought about writing 'schochking' but that seemed really lame. It's an in-joke).

Dissorophoids: body armour and 'flat porcupines'

Dissorophoids are most often represented in the literature by Cacops from the Permian of Texas. It was about 40 cm long and had a row of armour plates that grew in a line along the length of its back [reconstructions of Cacops are shown here: the one above is by John Sibbick, the one below is by Samuel Williston]. Cacops belongs to the Dissorophidae, a dissorophoid clade known from North America and Russia and with a range extending from the Upper Carboniferous to the Upper Permian. Their diagnostic median armour (sometimes presumed to afford protection from predators, or to provide support for trunk musculature), combined with their stout, well ossified limbs, absence of lateral-line canals and other features, indicates that that they were terrestrial. Their otic notch is sometimes enclosed by bone on all sides and almost certainly housed a tympanum - an ear drum - that was used in terrestrial hearing.

In Cacops and similar forms the median armour plates were fused to the tops of the neural spines, and in some dissorophids the spines became elongate, the distinctive sculpturing at their tips apparently representing the original armour scute. Hyper-elongate spines, presumed to have formed a sail-like structure superficially similar to that of the synapsid Dimetrodon, were present in Platyhystrix and Astreptorhachis. Though it has been argued that these taxa should be separated from the dissorophids and awarded their own 'family', the Platyhystricidae, this is not useful given that there are intermediate forms with mid-length neural spines, such as Aspidosaurus. What these animals did with their long neural spines is not known. Contrary to what it says in some popular books there is no indication that the spines were associated with the high degree of vascularisation needed for a thermoregulatory role, and Vaughn (1971) thought that they probably initially evolved to provide mechanical support during terrestrial locomotion [adjacent Platyhystrix reconstruction by Arthur Weasley].

Closely related to dissorophids were the amphibamids (here taken to include the micropholids, following Schoch & Rubidge 2005). Characterized by particularly short, undifferentiated ribs, strongly reduced palatal bones and other characters, amphibamids were less than 40 cm long and had proportionally large, robust limbs and short tails. Restorations of amphibamid species were produced by Daly (1994) in her description of the new Carboniferous taxon Eoscopus lockardi: her drawings (two of which are shown here: they depict Eoscopus lockardi with Amphibamus lyelli below) make the animals look something like big-headed, scaly-skinned, short-tailed salamanders, though different species differ in how long their legs appear.

Within some amphibamid species there is a large amount of variation in skull shape, with small individuals being far shorter-snouted than large individuals. Lateral-line canals were absent and in the large basal amphibamid Micropholis from Lower Triassic South Africa, the limb proportions are suggestive of competent terrestrial abilities [skull of Micropholis shown here, from Boy (1985)]. Some amphibamids (Amphibamus and Doleserpeton) were tiny, and exhibited a suite of peculiar features: very thin skull bones, proportionally huge orbits and huge palatal vacuities, and skull bones in which the external sculpture is poorly developed. These forms also possess pedicellate teeth: this is the tooth type characteristic of living amphibians (the tooth crown sits on a flexible base composed of uncalcified fibrous tissue). Micropholis lacked pedicellate teeth and the other mentioned characters (Schoch & Rubidge 2005).

The closely related trematopids (previously referred to by some as trematopsids) were more conservative, and were mostly restricted to the Late Carboniferous and Early Permian of the USA (a German member of the group was reported in 1998 and a Czech one more recently). Strongly adapted for terrestrial life, one of their most distinctive features is a relatively enormous, bizarrely elongate external nostril, the function of which remains unknown: Bolt (1974) suggested that it may have housed a salt gland [skull of the trematopid Phonerpeton from the Lower Permian of Texas shown here, from Dilkes (1990)]. Trematopid vertebrae were well ossified and the trunk region was covered by small, non-overlapping bony scutes in some species at least (like Anconastes vesperus from Late Carboniferous New Mexico). Trematopid skulls are also distinctive in that the otic notch is long and slit-like. In Acheloma, the notch is so small that the tympanum within the notch (assuming, that is, that it was present) would apparently have been too small to function effectively in the transmission of airborne sounds (Dilkes & Reisz 1987). Schoch & Rubidge (2005) found trematopids to be more basal within Dissorophoidea than were dissorophids and amphibamids.

Return to the water: neotenic micromelerpetontids (or not)

While - as noted earlier - euskelians were generally terrestrial animals, a few dissorophoid groups were secondarily aquatic. Long known informally as branchiosaurs, these rather small, salamander-like forms were sometimes regarded as the larvae of large-bodied temnospondyls. Indeed some 'branchiosaurs' have turned out to be the larvae of certain limnarchians, but the others represent two distinct, apparently neotenic dissorophoid clades: Branchiosauridae and Micromelerpetontidae.

Micromelerpetontids are known from the Upper Carboniferous and Lower Permian of Europe and only three genera are known: Limnogyrinus, Micromelerpeton [shown above, from here] and Branchierpeton. All are long-bodied with short limbs. Larval micromelerpetontids were tiny animals (less than 10 cm long) with poorly ossified skeletons and large external gills, but even in adults, lateral line canals and short external gills persisted, so they too were predominantly aquatic (Witzmann & Pfretzschner 2003). 'Large' micromelerpetontids (with skulls nearly 50 mm long) exhibiting features typical of a terrestrial lifestyle have been reported from Germany, and the question remains as to whether these represent primitive members of the group, or advanced forms that have switched from an aquatic lifestyle back to terrestriality, or simply the adults of the smaller aquatic forms.

If we ignore these large, terrestrial forms for the time being, the broad, short micromelerpetontid snout suggests that they were aquatic suction feeders, and they probably preyed on invertebrates, small fish and perhaps other small temnospondyls. Unlike living amphibians, we must remember that these animals possessed a scaly skin, so the adults would presumably have relied less on cutaneous respiration than do living aquatic amphibians. How micromelerpetontids are related to other dissorophoids has provide controversial: they have been regarded as the closest relatives of branchiosaurids or amphibamids, as an aquatic side-branch of the terrestrial dissorophids, and most recently as the most basal of all dissorophoids (Schoch & Rubidge 2005).

And - with branchiosaurids, eryopoids, dvinosaurs and all those tens of limnarchian clades still to go, I must leave. I know you want more, sorry.

For previous articles on temnospondyls and other non-amniote tetrapods please see...

Refs - -

Bolt, J. R. 1974. Osteology, function, and evolution of the trematopsid (Amphibia: Labyrinthodontia) nasal region. Fieldiana Geology 33, 11-30.

Boy, J. A. 1985. Ãber Micropholis, den letzten Ãberlebenden der Dissorophoidea (Amphibia, Temnospondyli; Unter-Trias). Neues Jahrbuch fur Geologie und PalÃ¤ontologie, Monatshefte 1985, 29-45.

Daly, E. 1994. The Amphibamidae (Amphibia: Temnospondyli), with a description of a new genus from the Upper Pennsylvanian of Kansas. The University of Kansas Museum of Natural History, Miscellaneous Publications 85, 1-59.

DeFauw, S. L. 1989. Temnospondyl amphibians: a new perspective on the last phases in the evolution of the Labyrinthodontia. Michigan Academician 21, 7-32.

Dilkes, D. W. 1990. A new trematopsid amphibian (Temnospondyli: Dissorophoidea) from the Lower Permian of Texas. Journal of Vertebrate Paleontology 10, 222-243.

- . & Reisz, R. R. 1987. Trematops milleri Williston, 1909 identified as a junior synonym of Acheloma cumminsi Cope, 1882, with a revision of the genus. American Museum Novitates 2902, 1-12.

Ruta, M., Jeffery, J. & Coates, M. I. 2003. A supertree of early tetrapods. Proceedings of the Royal Society of London B 270, 2507-2516.

- ., Pisani, D., Lloyd, G. T. & Benton, M. J. 2007. A supertree of Temnospondyli: cladogenetic patterns in the most species-rich group of early tetrapods. Proceedings of the Royal Society of London B 274, 3087-3095.

Schoch, R. R. 1999. Comparative osteology of Mastodonsaurus giganteus (Jaeger, 1828) from the Middle Triassic (Lettenkeuper: Longobardian) of Germany (Baden-WÃ¼rttemberg, Bayern, ThÃ¼ringen). Stuttgarter BeitrÃ¤ge zur Naturkunde Serie B (Geologie und PalÃ¤ontologie) 278, 1-175.

- . & Rubidge, B. S. 2005. The amphibamid Micropholis from the Lystrosaurus Assemblage Zone of South Africa. Journal of Vertebrate Paleontology 25, 502-522.

Vaughn, P. P. 1971. A Platyhystrix-like amphibian with fused vertebrae, from the Upper Pennsylvanian of Ohio. Journal of Paleontology 45, 464-469.

Witzmann, F. & Pfretzschner, H.-U. 2003. Larval ontogeny of Micromelerpeton credneri (Temnospondyli, Dissorophoidea). Journal of Vertebrate Paleontology 23, 750-768.

Yates, A. M. & A. A. Warren. 2000. The phylogeny of the "higher" temnospondyls (Vertebrata: Choanata) and its implications for the monophyly and origins of the Stereospondyli. Zoological Journal of the Linnean Society 128: 77-121.

tetrapodzoology Wed, 09/30/2009 - 02:35

Tags

Palaeozoic tetrapods

Categories

Life Sciences

Daly's amphibamids remind me of some of the quadrupedal herps that wander through some of Escher's figures.

One of the people I met for the first time at the meeting was the legendary David MarjanoviÄ.

Bummer, no picture of this semi-mythological being. I want to know if he has pointed ears, like Spock.

I though[t] about writing 'schochking' but that seemed really lame. It's an in-joke.

Heh, for once I get the Tet Zoo in-joke. I think.

her drawings (two of which are shown here: they depict Eoscopus lockardi with Amphibamus lyelli below) make the animals look something like big-headed, scaly-skinned, short-tailed salamanders

...or like the ancestors of Kermit the Frog.

Pfretzschner

'Would you like to buy a wovel?'

wovel

...and I would need to buy a spellchecker.

I need to look up Schoch (1999). Distal carpal 4 is ossified and the others are not? That would mess majorly with everything we thought we knew about limb evo-devo.

More recent phylogenies (Ruta et al. 2003, 2007), while supporting

They don't support anything, they're supertrees (as the titles helpfully mention). They show the consensus of recent results, but they aren't results of a phylogenetic analysis themselves; they are of no interest outside history of science (or when you urgently need a comprehensive phylogenetic hypothesis, would need to make your own data matrix, and can't afford to do that).

Their diagnostic median armour (presumed to afford protection from predators)

Erm, no â it's supposed to be a crocodile-like exoskeleton, providing support for the backbone, much like in chroniosuchians. As armour it belongs on Failblog, what with hardly covering anything.

absence of later line canals

Did you run a spellchecker over the lateral-line canalsâ¦?

Their otic notch is sometimes enclosed by bone on all sides and almost certainly housed a tympanum - an ear drum - that was used in terrestrial hearing.

Possible. In other words, I can't imagine another function for this huge oval structure. However, being legendary, I'd like to see a bit more information about stapes size and anatomy before I commit to that interpretation. Sigurdsen (2009) has an illustration of how tiny, tiny, tiny the stapedes of a goliath frog are.

The closely related trematopids [â¦] were mostly restricted to the Late Carboniferous and Early Permian of the USA (a German member of the group was reported in 1998).

And a Czech one, good old Mordax, in an SVP meeting abstract in 2007. Should get published soon, I suppose.

Whether this was a primitive feature, or whether trematopids become secondarily deaf, is unknown.

Well, a rather small "otic" notch is plesiomorphic, and Trematopidae and Dissorophidae + Amphibamidae ?including Branchiosauridae appear to be sister-groups, so an autapomorphic enlargement (and perhaps gain of a tympanum) look like the most parsimonious interpretation to meâ¦ have I overlooked something?

'Large' micromelerpetontids (with skulls nearly 50 mm long) exhibiting features typical of a terrestrial lifestyle have been reported from Germany, and the question remains as to whether these represent primitive members of the group, or advanced forms that have switched from an aquatic lifestyle back to terrestriality.

Or just simply adults (real adults this time), as an SVP meeting abstract from 2007, with a title that starts with "Finally grown up", argues.

Metamorphosed adults of the branchiosaurid Apateon gracilis were reported in 1991 and (in more ontogenetic detail and in English) in 2006; Apateon caducus, however, really was neotenic according to that same 2006 paper.

Pointed ears would fit, but I have to disappoint. And while my hair is smooth, it's not black. And I'm not even capable of lifting just one eyebrow <sniff>

'Would you like to buy a [v]o[w]el?'

The z is just for fun (some kind of 16th-century affectation or something). Ignore it. :-)

Thanks for those comments. At the time of writing (doubtless it will change in 20 minutes or so), the article is getting top billing in that 'Now on ScienceBlogs' line at the top! Anyway, I'll go make a few corrections/updates now, thanks David and others. Dartian: I do have photos of David and have put one on Facebook. I didn't see pointed ears. Nor does he look like his Spec version :(

On the carpals of Mastodonsaurus, Schoch (1999) says that they're often missing due to small size, and he doesn't say that distal carpal 4 was definitely absent.

And I agree about the Escheresqueness of Daly's amphibamids :)

Trematopidae and Dissorophidae + Amphibamidae ?including Branchiosauridae appear to be sister-groups

Or not. Just started reading the Schoch & FrÃ¶bisch paper in the Systematic Biology issue of June 2009 (Syst. Biol. always takes its time to arrive over here). In those trees where the relationships are resolved, Dissorophidae and Trematopidae are sister-groups with respect to Amphibamidaeâ¦

Nor does he look like his Spec version :(

Unfortunately, though, I'm still uncannily similar to it.

Schoch (1999: 130) doesn't mention any carpals except intermedium and ulnare, but says there's an articulated (if fragmentary) specimen. Eryops is not mentioned in the text at all. Confusing.

Good call on the Escher. They also make me think of Dia de Los Muertes.

@David MarjanoviÄ: "They don't support anything, they're supertrees (as the titles helpfully mention). They show the consensus of recent results, but they aren't results of a phylogenetic analysis themselves; they are of no interest outside history of science (or when you urgently need a comprehensive phylogenetic hypothesis, would need to make your own data matrix, and can't afford to do that)."

Holy Words!

damn it, darren, this is so much fun to read it's almost pr0nographic! it boggles the mind you don't get paid to do this.

What is that taxon with the very long snout? I am super interested...

Incidentally, got a bigger version of the first pic? Would make a nice wallpaper.

What is that taxon with the very long snout?

It says "Trematosauridae" next to it, and trematosaurids are indeed long-snouted marine temnospondyls, but this one almost overdoes it, IIRC.

I like that dissorophids are figured looking just the way dinosaurs were imagined a century and a half ago.

<facepalm> That's what's always so familiar about Cacops! It looks like Owen's Megalosaurus!!!

:-o

Except for the sprawling limbs, it's really remarkably similar.

I was thinking of the Waterhouse Hawkins Iguanodon, myself, but I see the precervical resemblance to M..

How can those of us who would sooner gouge our eyes out with the jagged shard of our own ulna than sign up on Facebook get to see the photo of the legendary David MarjanoviÄ?

Very interesting stuff.

Is there any indication that there could be some kind of neotenic populations of Micromelerpetontids, in a similar way as some extant caudata populations (as in Mesotriton alpestris)?

RE: neoteny/paedomorphosis in micromelerpetontids:

I don't know if this is the case for micromelerpetontids, but at least one species of branchiosaurid seems to show this sort of facultative lifestyle, which Dave already mentioned a few posts up. Of course, this depends on the existence of micromelerpetontids and branchiosaurids as "real" groups; recent analyses are placing both as derived amphibamids way up on the batrachomorph stem (see the Frobisch & Schoch paper previously cited). So it would seem that there is some confusion about how exactly the miniaturized and neotenic dissorophoids all fit together. There are certainly some confounding factors (that is, convergent neoteny, see Wiens et al. 2005) that could be hindering recovery of a "true" phylogeny. So the problem is sort of difficult to resolve at some level, because our understanding of the evolutionary processes driving perceived neoteny in the clade depend on the phylogeny, and our phylogeny is itself pretty bunged up by ontogenetic processes within the clade.

On that, at least, Dave and I will agree.

RE: Platyhystrix, Astreptorhachis, and Aspidosaurus.

Dissorophid armor is not all created equal. In the more derived dissorophoids (Cacops, Alegeinosaurus, Dissorophus, Broiliellus, etc) there are two layers of dorsal ossifications, with a lower osteoderm ossifying to the neural spines of the thoracic vertebrae and the upper osteoderms forming the typical "carapace." In Platyhystrix, Astreptorhachis, and Aspidosaurus, the external armor fuses directly to the neural spine. So, it's not *just* the general appearance of the armor which differentiates the sailbacks from the rest, there are some more robust differences.

Also, contra Dave, armor of Dissorophus is pretty wide and covers a great deal of the dorsal region of the animal. There are also additional lateral ossicles on other dissorophids suggesting that the dorsal armor was probably a little more comprehensive than just the single median row. There are certainly a plethora of alternate explanations for this (Dave cited biomechanical properties of the thoracic skeleton, and there are other possibilities as well) but I'm not sure there is enough data to completely reject a defensive utility of those structures based on the current published literature at this time.

Excellent post - fascinating creatures.

Are you sure you met the MarjanoviÄ - surely it is a mythical being? If you didn't manage to bag a specimen then surely the least we can ask for is a photo to prove it exists (I was going to say a DNA sample, but decided that sounded wrong on so many levels). Having had the odd verbal duel (friendly, obviously), I would have liked to know what he looks like.

As for your previous post about Bristol zoo - its one of my favourite zoos - I guess the fact that we used to go there a couple of times every year when I was a kid, and more recently occasionally take my nephews, means it has lots of fond memories for me. It no longer has elephants etc, but it has sloths, fruit bats and aye ayes which I think more than makes up for it.

those of us who would sooner gouge our eyes out with the jagged shard of our own ulna than sign up on Facebook

That includes myself, just for the record.

So the problem is sort of difficult to resolve at some level, because our understanding of the evolutionary processes driving perceived neoteny in the clade depend on the phylogeny, and our phylogeny is itself pretty bunged up by ontogenetic processes within the clade.

On that, at least, Dave and I will agree.

Yeah, and there are other such cases. For example, some of the similarities between lysorophian lepospondyls and lissamphibians smell of paedomorphosis â if, that is, we assume that lysorophians and lissamphibians had similar ontogenies! If we don't, we're reduced to helpless guesses, even though there are some tetrapod-wide indicators of paedomorphosis in lysorophians (persistent suture between centrum and neural archesâ¦ persistent suture between left and right neural arches, for crying out loud).

Also, contra Dave, armor of Dissorophus is pretty wide and covers a great deal of the dorsal region of the animal.

Oops, true. Exhibit A: Dissorophus multicinctus which resembles armadillos in more than the name. Thanks for reminding me, I was thinking too much of just Cacops (illustrated above).

Hey Darren, I enjoyed your article. One question: did terrestrial temnospondyls (or any at all) have lizard-like "lips"?

Quoting Dave:

Yeah, and there are other such cases. For example, some of the similarities between lysorophian lepospondyls and lissamphibians smell of paedomorphosis â if, that is, we assume that lysorophians and lissamphibians had similar ontogenies! If we don't, we're reduced to helpless guesses, even though there are some tetrapod-wide indicators of paedomorphosis in lysorophians (persistent suture between centrum and neural archesâ¦ persistent suture between left and right neural arches, for crying out loud).

Right. Lysorophians are almost certainly paedomorphic. The persistence of the suture between the centrum and neural arch is one of many paedomorphic features; there are a lot of portions of the dermal skull that are simply incompletely ossified or which never ossify (circumorbital bones, portions of the dermal palate, etc), and retention of a well-developed branchial skeleton into adulthood all point to paedomorphosis as a major driving factor in the origin of the lysorophians. There are, of course, multiple paths towards miniaturization in amphibians, but not all lysorophians are miniature (see: Molgophis and 'Brachydectes' elongatus), nor are all modern paedomorphic amphibians 'miniature.' Ultimately, Dave and I disagree on the importance of these characteristics in context of lissamphibian origins, but paedomorphosis as a major driver in diversification of paleozoic tetrapods is itself interesting considering that paedomorphosis is a major source of variation in modern amphibians as well.

It should be noted that Dissorophis itself is by far the most spectacular. It's armor rivals that of Peltobatrachus, and is deserving of Bakker's neologism "Armadillo toad".

What makes Daly's amphibamids (and the six-legged roll-ups in Escher's 'House of Stairs') look particularly odd is that the fore and hindlimbs are drawn almost the same, with the knees bending parallel to the elbows. Isn't that just wrong?

Checking Escher images, the cute little guys in 'Reptiles' remind me more of Mekosuchus... whose nasal bones I found recently. Probably not so stumpy in real life.

And I spent just long enough on Facebook to find that picture of David. Darren, can you confirm that he was actually shooting laser beams from his eyes?

there are a lot of portions of the dermal skull that are simply incompletely ossified or which never ossify (circumorbital bones, portions of the dermal palate, etc)

Careful there. All this is true if we assume a lissamphibian- or temnospondyl-like ontogeny for lysorophians (or at least their non-paedomorphic ancestors). Well, assuming a lissamphibian-like one begs the question, and the temnospondyls are rather far away on the tree. Unfortunately, the only known lepospondyl skull ossification sequence (a very partial one -- three stages) is that of the highly derived aÃ¯stopod Phlegethontia, and that one is just plain weird, being neither similar to those of lissamphibians or temnospondyls, nor ever leading through a stage similar to what lysorophians look like, so it doesn't help.

Sure, there are a few characteristics of lysorophians that make sense if we assume 1) paedomorphosis and 2) a lissamphibian-like ontogeny, such as the extremely broad cultriform process of the parasphenoid (exaggerated all the way to completely obliterating the interpterygoid vacuities) or the arrangement of the vomerine teeth, which look just like in larval/neotenic salamanders (...just salamanders... not frogs or caecilians). Assumption number 1 is supported by a couple of vertebrate-wide indicators of morphological immaturity, most drastically by the suture between left and right neural arches. But where exactly do we take assumption number 2 from? We have to beware of circular logic here.

In short, we don't know exactly which character states of lysorophians are due to their undisputed paedomorphosis and which are not.

Ultimately, Dave and I disagree on the importance of these characteristics in context of lissamphibian origins

I don't think we do.

What makes Daly's amphibamids (and the six-legged roll-ups in Escher's 'House of Stairs') look particularly odd is that the fore and hindlimbs are drawn almost the same, with the knees bending parallel to the elbows. Isn't that just wrong?

Of course it is. But at least she didn't forget the scales like just about everyone else does.

BTW, I want that picture. :-)

RE: Dave:

Careful there. All this is true if we assume a lissamphibian- or temnospondyl-like ontogeny for lysorophians (or at least their non-paedomorphic ancestors). Well, assuming a lissamphibian-like one begs the question, and the temnospondyls are rather far away on the tree. Unfortunately, the only known lepospondyl skull ossification sequence (a very partial one -- three stages) is that of the highly derived aÃ¯stopod Phlegethontia, and that one is just plain weird, being neither similar to those of lissamphibians or temnospondyls, nor ever leading through a stage similar to what lysorophians look like, so it doesn't help.

Well, sort of. We also have developmental sequences for non-tetrapods (e.g. Eusthenopteron, Dipterus, numerous basal actinopterygians, and various modern taxa, and while there are certainly non-homologies between a lot of the specific bones, the general regions of the skull and their order of ossification seems somewhat conserved, as does the order of ossification of tissue type derivatives (i.e. splanchnocranium vs. neurocranium vs. dermatocranium). So while the temnospondyl and lissamphibian data may not be directly applicable to lepospondyls, I think largely that there are some hard and fast rules concerning the distribution of ossification in space and time in the vertebrate skull. I'm really not convinced at this moment that lepospondyls have flat-out changed patterns of neural crest cell migration early on in tetrapod evolution and thus have acquired a completely unique sequence of chondrification and ossification. I am convinceable, but I'd need to see some significant developmental work backing that up.

I'm really not convinced at this moment that lepospondyls have flat-out changed patterns of neural crest cell migration early on in tetrapod evolution and thus have acquired a completely unique sequence of chondrification and ossification.

Phlegethontia has (Anderson 2002). I'm not saying any other lepospondyl is like that, but Ph. is majorly weird.

Anyway, I just found an example where lysorophians show evidence of deviating from temnospondyl (and apparently lissamphibian, and to some degree even amniote) ontogeny: rib length relative to vertebra length. Relative rib length increases in temnospondyl ontogeny (known from branchiosaurids, micromelerpetontids, Archegosaurus, and Sclerocephalus), fitting the idea that paedomorphosis is responsible for the extremely short (or, in most crown-group frogs and except for the sacral pair, altogether absent) ribs of lissamphibians; lysorophians have very long ribs instead (as does Batropetes, BTW). Peramorphosis for the ribs and paedomorphosis for the rest of the body? Even though elongate lissamphibians have tiny ribs? Sounds unlikely to me.

Now, ribsâ¦ Jennifer Olori is working on lepospondyl postcranial ossification sequences (a few are known, mostly Microbrachis and Hyloplesion, apart from Phlegethontia), so we can expect to learn something on that soon. For cranial ossification sequences we'll have to wait for more discoveries; Phlegethontia means that all phylogenetic bracketing gives ambiguous results.

David, do you support more, with nowadays data, the lepospondyl origin of lissamphibia?

At the moment, yes, though the distance to the temnospondyl hypothesis (in terms of additional steps needed on at least some data matrices) is not very large.

Also, within the lepospondyl hypothesis, the "nectrideans"-including-aÃ¯stopods could be closer to Lissamphibia than the lysorophians are.

RE: Dave:

Phlegethontia has (Anderson 2002). I'm not saying any other lepospondyl is like that, but Ph. is majorly weird.

I suppose that the early complete ossification of the vertebrae is weird, but the rest of the organism is relatively sensible in ossification sequences. There are also potentially some distinct (functional) reasons for such early ossifications. I'm also somewhat skeptical of the idea that we're seeing as complete an ossification sequence as we think. Basically, there's a lot we don't know about aistopods that needs to be resolved.

Anyway, I just found an example where lysorophians show evidence of deviating from temnospondyl (and apparently lissamphibian, and to some degree even amniote) ontogeny: rib length relative to vertebra length. Relative rib length increases in temnospondyl ontogeny (known from branchiosaurids, micromelerpetontids, Archegosaurus, and Sclerocephalus), fitting the idea that paedomorphosis is responsible for the extremely short (or, in most crown-group frogs and except for the sacral pair, altogether absent) ribs of lissamphibians; lysorophians have very long ribs instead (as does Batropetes, BTW). Peramorphosis for the ribs and paedomorphosis for the rest of the body? Even though elongate lissamphibians have tiny ribs? Sounds unlikely to me.

Well, I think this is one of those cases where we have reason to believe that some aspects of lysorophian anatomy have been modified by paedomorphosis, but not all aspects. I'm not really sure why this should be all that surprising, although I do think this should raise questions as to the exact morphology of the thoracic musculature in lepospondyls in general.

Now, ribsâ¦ Jennifer Olori is working on lepospondyl postcranial ossification sequences (a few are known, mostly Microbrachis and Hyloplesion, apart from Phlegethontia), so we can expect to learn something on that soon. For cranial ossification sequences we'll have to wait for more discoveries; Phlegethontia means that all phylogenetic bracketing gives ambiguous results.

So I've heard. Once again concerning Phlegethontia, though, I don't think it is as completely weird as you're making it out to be. I am curious to see what the basal microbrachomorphs are going to turn up vis a vis development, though.

I suppose that the early complete ossification of the vertebrae is weird, but the rest of the organism is relatively sensible in ossification sequences.

Jugal before premaxilla? Sensible? Zonked out, I tell you.

I don't have the 2002 or the 2003 paper here, but the 2007 book chapter illustrates the three known stages of skull ossification again (in lateral view, which is most likely all that is known):

Smallest: complete caudal half of braincase except crests, frontal, maxilla, surangular, angular.

Intermediate: the above + lacrimal, dentary, rostrodorsal and rostroventral corners of "postfrontal" (likely separate postfrontal and postorbital), jugal, all of ?quadratojugal/squamosal except dorsal process; complete, unbroken ventral margin of orbit and cheek region.

Largest: the above + all the rest: premaxilla, complete and single "postfrontal", dorsal process of ?quadratojugal/squamosal, sagittal and nuchal crests of braincase.

Pretty much all that's normal here is the early appearance of the frontal, don't you think?

I'm also somewhat skeptical of the idea that we're seeing as complete an ossification sequence as we think.

Nobody has said it's complete. I, for one, keep whining about how it's only 3 stages :-)

Basically, there's a lot we don't know about aistopods that needs to be resolved.

Understatement :-)

I'm not really sure why this should be all that surprising,

In principle, paedomorphosis and peramorphosis for different characters of the same animal is not surprising, but I'd expect that to apply to things like dermal vs endochondral skeleton or limb ratios; I just can't think of a reason why the ribs of all things should be peramorphic in an otherwise paedomorphic animal, especially when that never happens in, one would think, comparable lissamphibians.

although I do think this should raise questions as to the exact morphology of the thoracic musculature in lepospondyls in general.

Good point.

BTW, I wouldn't use the term "microbrachomorphs". Even the original paper, Carroll & Gaskill (1978), expresses skepticism about the monophyly of that grouping; and while ("microsaur" phylogeny being extremely volatile in general) Hyloplesion, Microbrachis and Odonterpeton do tend to end up somewhere close to each other (like forming a paraphyletic series), the brachystelechids are usually far off (sometimes forming part of Anderson's Recumbirostra, sometimes not).

Hello darren: could you please tell me what the name of the crown-group tetrapods is? Thank you!

What that name is depends on who you listen to. If you listen to Michel Laurin, it's Tetrapoda (and temnospondyls, anthracosaurs, even seymouriamorphs are not tetrapods). If you listen to most other people, the crown-group currently lacks a name.

Given the current degree of uncertainty about where the Lissamphibia fit on the tree, would it be too much to ask all reputable paleontologists to REFRAIN from naming the crown group of tetrapods for a while? If a name got into currency and there was then a major change of opinon about the contents of the crown group, I think the literature could become very confusing: imagine reading a paper, looking at the date, and asking yourself "What do you suppose the author of this thought was IN xxxx?"

A few years of writing "Crown Tetrapoda" or "Lissamphibia+Amniota" with no one-word name until the situation is clarified would surely be preferable!

Thank you for your answers, i appreciate them
I'd have another question: is is true dat anurans and caudates are temnospondyls and gymnophions are lepospondyls? Sorry for being possibly wrong

This is one of the three hypotheses -- and if you had read the previous comments, you'd already know that.

While we're at it, is it official, down on paper, registered with the Phylocode people, that "Lissamphibia" is the last common ancestor of frogs, salamanders and Gymnophiona with all of its descendents? Because, if it is, and if a phylogenetic hypothesis according to which they aren't closely related is substantiated, the paleontological community will have to issue an embarrassed press release:
"About those Carboniferous and Permian types that we all called "Amphibians" for most of the 20th C, and that we professionals spent the last couple of decades trying to tell you weren't really Amphibians-- well, they are now Amphibians again."

What is that taxon with the very long snout? I am super interested...

It says "Trematosauridae" next to it, and trematosaurids are indeed long-snouted marine temnospondyls

Indeed: it is a reconstruction of Aphaneramma, a lonchorhynchine trematosaurid from the Early Triassic of Svalbard (probably made from the figures of the monographs of SÃ¤ve-SÃ¶derbergh, 1935 or 36). At the time of DeFauw (1989), it was the only trematosaurid for which postcranial material was known - until the description of new material of Wantzosaurus by Steyer (2002) and Trematolestes by Schoch (2006).

Some trematosaurids were found in marine beds (where they co-occur with ammonoids), but not all: some of them were found in lacustrine (Cosgriffius from Arizona), fluvial (Trematosaurus) or fluvio-estuarine deposits (Trematolestes from Germany).

trematosaurids are indeed long-snouted marine temnospondyls, but this one almost overdoes it, IIRC.

Yeah, but did you even see Cosgriffius, or Platyoposaurus ? (OK, the latter is not a trematosaurid, but an archegosaurid, but it's pretty amazing too, isn't it ?)

Platyoposaurus is made of awesome!

To my shame, I hadn't noticed that the triangle-headed Cosgriffius is a trematosaurid. I'm not very familiar with stereospondyls -- most phylogenetic work on limbed vertebrates in general ignores them completely.

While we're at it, is it official, down on paper, registered with the Phylocode people, that "Lissamphibia" is the last common ancestor of frogs, salamanders and Gymnophiona with all of its descendents?

Something similar will be, with the important difference that the definition will contain external specifiers: if (for example) Eryops or Homo fall inside the smallest clade that contains frogs, salamanders & caecilians, that clade must not be called Lissamphibia, and the name self-destructs.

The PhyloCode will only be implemented upon publication of the companion volume. Could take another year or two.

By the way, I have stuff on trematosaurs just about done. Just need to get through eryopoids, dvinosaurids,tupilakosaurids, trimerorhacids, eobrachyopids, archegosauroids, lapillopsids and capitosaurs first.

PhyloCode volume is indeed nearly there, but we're not sure how nearly there, especially given that new submissions are still being produced. Had a long chat about it with Jacques at SVP and have ended up taking on the Theropoda contribution. Email me if you work on theropods and want to be involved.

Names that self-destruct... Fascinating idea: I must get serious and learn how PhyloCode is supposed to work in detail!
Certainly that would help with the "confusing literature" problem I imagined: in the case supposed (in comment #37), a reader finding "Lissamphibia" in an article would at least have a "heads up" that they were dealing with an article written before...
(Thanks, DM: I hadn't been aware of the relevant feature of PhyloCode. I plead amateur status.)

I must get serious and learn how PhyloCode is supposed to work in detail!

http://www.ohiou.edu/phylocode

Can be read in one evening.

There's also a Wikipedia article on phylogenetic nomenclature, but even though I created it, I can't recommend it right now, because some ignoramus added irrelevant mentions of "cladistics" and even "cladism" to it, and I have yet to check what else is now wrong or misleading.

Just need to get through [...] tupilakosaurids [...] eobrachyopids [...] first.

Impressively detailed list... Did you manage to attend Anne Warren's SVP talk about tupilakosaurids and brachyopids (not eo-)?

Darren:

have ended up taking on the Theropoda contribution

All the birds too?

I hope this phylocodery won't eat up precious time that could be spent writing blog posts instead...

Well, I (and a group of colleagues) are only worried about the definition of Theropoda itself, not the definitions of the many constituent clades. Good call though :)

As for 'eating up precious time that could be spent writing blog posts', it's funny to hear you say this. I'm under huge pressure for lots of reasons (and from lots of people) to blog LESS and concentrate on paper-writing MORE. Blog-writing gets me paying work (because publishers and so on see my stuff), but it doesn't help with academic kudos.

As for 'eating up precious time that could be spent writing blog posts', it's funny to hear you say this. I'm under huge pressure for lots of reasons (and from lots of people) to blog LESS and concentrate on paper-writing MORE. Blog-writing gets me paying work (because publishers and so on see my stuff), but it doesn't help with academic kudos.

I realised only after pressing the 'Post' button that I should have been more clear. With 'precious time' I meant the time that's left over for you from taking care of your family, writing technical papers, and various other things such as finding the time to eat and to sleep. I've never presumed anything else than that all those have priority over blogging.

And, you see, for a moment there I was envisaging a scenario where you're pouring through mountains of ornithological literature for the single purpose of being able to create phylogenetic definitions for every muttonbird and buttonquail and whatnot bird taxon...

pouring through

D'oh! 'poring through'.

'Me fail English? That's unpossible!' -Ralph Wiggum

Ruta et al.'s (2007) temnospondyl supertree is just begging to be put onto a T-shirt.. but it would have to be one with a fine weave.

Has anyone suggested yet that sailbacks could have had a sonic use.. as sounding boards, acting as directional emitters, or receivers, for the vibrations of their mating calls, say? Did extinct foms do so? Are there osteological correlates of the vocal sacs (elastic throat pouches) in extant amphibians, that could bear on this?
If some species had hearing that was not acute then tactile detection of booming sound pulses might be useful.. and a big area of sensitive skin held taut between rigid spines, it seems to me, might be a handy organ for that.

David Marjanovic--
Thank you for the references (comment #45)! Have only skimmed so far, but will return to study in detail.
---Note 2.1.2 (in Articles) should be printed in bold Italics, all capitalized!
---4.3(a) might be an embarrassment: I suspect Mike Taylor may be right about the future relative importance of electronic and paper publication.

Has anyone suggested yet that sailbacks could have had a sonic use..

AFAIK not, and that's a good idea! Considerably less likely than the usual one (use as a visual signal), but sails as receivers ought to work.

Note 2.1.2 (in Articles) should be printed in bold Italics, all capitalized!

Nowadays it's not news anymore. The mid-late 1980s, when some people wrote "every node must be named", are over.

4.3(a) might be an embarrassment:

The idea is that you should not need a special apparatus (beyond glasses...) to read any valid publication. It's entirely possible that this will become an embarrassment.

Note 2.1.2 (from the PhyloCode page):

It is not necessary that all clades be named.

and David:

The mid-late 1980s, when some people wrote "every node must be named", are over.

That's all fine and well, but are there also some universal rules about what nodes/clades must be named? If there aren't, how is 'taxonomic freedom' to be avoided?

Allen:

4.3(a) might be an embarrassment

Article 4.3(a):

The following do not qualify as publication: (a) dissemination of text or images solely through electronic communication networks (such as the Internet) or through storage media (such as CDs, diskettes, film, microfilm and microfiche) that require a special device to read

As I interpret it, the key word word in that passage is 'solely'. In other words, that while electronic publication is allowed and even encouraged, the publications should also exist as physical copies. Which is perfectly sensible and indeed farsighted.

I suspect Mike Taylor may be right about the future relative importance of electronic and paper publication.

He may be. But that remains to be seen.

That's all fine and well, but are there also some universal rules about what nodes/clades must be named?

No, why?

If there aren't, how is 'taxonomic freedom' to be avoided?

What do you mean -- how to stop people from immortalizing themselves by naming boatloads of clades and creating frightful messes in the future? Peer review is required for valid publication, for example. Also, there are recommendations against "wholesale conversions" of series of preexisting names, especially by people who haven't worked on the clades in question.

David:

What do you mean -- how to stop people from immortalizing themselves by naming boatloads of clades and creating frightful messes in the future?

Yes, that's what I mean. Who can objectively decide which clades 'need' to be named and which don't? Peer reviewers? They are themselves fallible, subjective human beings. You've said before here on Tet Zoo that splitting and lumping will be 'impossible' under phylogenetic nomenclature; maybe I'm missing something but I don't see how that is possible unless there are some hard and fast rules about what can be named and what can't (e.g., a rule that says that a species pair is too small a clade to be named).

To take a real-world example of a frightful nomenclatural mess: What would be the appropriate number of named clades within the great ape clade Hominoidea (i.e., the LCA of Hylobates and Homo plus all their descendants)? Who on earth can objectively decide that? There are nearly as many opinions as there are experts working on the systematics of extinct and extant hominoids and there certainly is no shortage of already proposed clade names. Is, say, Hominini a superfluous or a necessary clade name? What about Gorillini? Is there a clade called Australopithecini, or, if there isn't, do we need one? What about Hominina? What's the PhyloCode companion volume's stance on the issue of hominoid nomenclature?

This sort of thing has been discussed in the literature on phylogenetic nomenclature; if I remember correctly there's coverage of it in Padian et al. (1999) and Joyce et al. (2004). Because workers only tend to use those clade names that 'matter' (i.e., for the stable nodes that get supported in most analyses), the many others that get named fall by the wayside, and it doesn't matter that they were ever named. If your analysis doesn't find an Australopithecini or Hominina, do those names matter? On the other hand, if your analysis does support those clades, is it a bad thing if the names are already there? Even better if they have a published definition.

Having said all that - most workers seem to be behaving with restraint these days. We went through a phase in the 1980s where every single node was getting named (see Sereno (1986) on ornithischians and Gaffney & Meylan (1988) on turtles). That seems to have died out (so far as I know).

Refs - -

Gaffney, E. S. & Meylan, P. A. 1988. A phylogeny of turtles. In Benton, M. J. (ed) The Phylogeny and Classification of the Tetrapods, Volume 1: Amphibians, Reptiles, Birds. Clarendon Press (Oxford), pp. 157-219.

Joyce, W. G., Parham, J. F. & Gauthier, J. A. 2004. Developing a protocol for the conversion of rank-based taxon names to phylogenetically defined clade names, as exemplified by turtles. Journal of Paleontology 78, 989-1013.

Padian, K., Hutchinson, J. R. & Holtz, T. R. 1999. Phylogenetic definitions and nomenclature of the major taxonomic categories of the carnivorous Dinosauria (Theropoda). Journal of Vertebrate Paleontology 19, 69-80.

Sereno, P. 1986. Phylogeny of the bird-hipped dinosaurs (Order Ornithischia). National Geographic Research 2, 234-256.

Gower & Wilkinson (1996) also included a discussion of why naming (just about) every node is irresponsible and to be avoided...

Gower, D. J. & Wilkinson, M. 1996. Is there any consensus on basal archosaur phylogeny? Proceedings of the Royal Society of London/ B 263, 1399-1406.

Splitting & lumping refer to taking a name and applying it to a different clade than before even though our knowledge of the phylogeny has not changed. That is indeed impossible in PN. Once, for example, Hominoidea has been defined as the MRCA of Homo and Hylobates plus all its descendants, you can't shift the name to, say, the MRCA of Homo and Pongo plus all its descendants, because you can't change the definition.

Cruel abuse of temnospondyl in cheesy German talent show:

http://www.welt.de/fernsehen/article4284636/Sommermaedchen-Das-Fernsehe…

Err... 'Cruel'?

I disagree. Having five fingers per hand, this thing is not a temnospondyl (unless Caerorhachis is one). Apart from its size, it could be a very young Eucrittaâ¦ or a seymouriamorph maybeâ¦

However, dragging anything into Pro7 is most certainly cruel. <vehement nodding>

> Err... 'Cruel'?

Getting dragged out of your pond and into Pro7 by a bunch of amniotes (even if they are moderatly attractive by amniote standards)? Most definitely cruel... :D

> Having five fingers per hand, this thing is not a
> temnospondyl

So all those recostructions of five-fingered temnospondyls in the literature (Bakker's *Cacops* in TDH, waving its five-fingered hand in a semaphore-like movement, to name but one example) and on the internet are wrong :-O?

http://en.wikipedia.org/wiki/Trematopsidae
http://en.wikipedia.org/wiki/Acheloma
http://en.wikipedia.org/wiki/File:Eryops_megacephalus_skeleton_front.JPG

To finally correct myself...

And a Czech one, good old Mordax, in an SVP meeting abstract in 2007. Should get published soon, I suppose.

It's Mordex laticeps. And it still hasn't been published.

So all those recostructions of five-fingered temnospondyls in the literature (Bakker's *Cacops* in TDH, waving its five-fingered hand in a semaphore-like movement, to name but one example) and on the internet are wrong :-O?

Yes.

OK, the early-20th-century reconstructions of the hand of Eryops actually show a prepollex; that would make five "fingers" total. But the disarticulated material needs to be completely redescribed, and AFAIK nobody's doing that.

All actually known and not too disarticulated temnospondyl hands show four fingers, just like how the feet show five toes.

Sea Dragons of Avalon, an Arthurian adventure (part I)

tetrapodzoology — Tue, 04 Aug 2009 10:57:00 +0000

Sea Dragons of Avalon, an Arthurian adventure (part I)

I promised myself back in 2007 that I'd cut down on the number of conferences I attend. There's a problem with that: I'm pretty bad at keeping promises (at least, to myself). This year I'm attending a ridiculous four conferences, and I've just returned from the first of them (please remind me why I have no money, and no spare time). Entitled Sea Dragons of Avalon: the early radiations of the marine reptiles and recovery from the Triassic-Jurassic faunal crisis, with special reference to Street in Somerset and the wider British record, this Palaeontological Association (Pal Ass) seminar included a day of talks on the British marine record, as well as an additional day of field trips to the surrounds (for previous pre-emptive thoughts on the meeting, see here [May 2009], here [July 2009] and here [August 2009]). Yes, more ichthyosaurs and plesiosaurs than you can shake a proverbial stick at...

Any conference that discusses marine reptiles and faunal changes across any given boundary is a good thing, of course, but this meeting was actually much more: its raison d'Ãªtre was to raise a glass to Arthur Cruickshank, a mentor and academic uncle to so many people who work in vertebrate palaeontology today [in the adajcent image, Arthur cuts a specially made cake. Yes, a cake with a historically significant plesiosaur on it: not every day you see that]. Arthur's impact on the plesiosaur world is considerable, and - in a career spanning five decades - he's also produced important contributions on archosaurs and synapsids. It seems high time that his role and influence be properly acknowledged. Because of constraints arising from Pal Ass's charitable status, and (quite separately) from problems that can arise from mixed Festschrifts featuring disparate presentations, we very properly split the meeting into two financially independent elements. It consisted of the Pal Ass seminar proper (held nominally in Arthur's honour, but with an entirely 'logical' programme), and a preceding informal Festschrift-style lunch party and more mixed set of papers. Well done to Mike A. Taylor, Leslie NoÃ¨, David Hill and Jeff Liston for the organisation, to Pal Ass for sponsorship... oh yes, and to me (though my role was very minor).

So, we had two days of talks. As usual, I'm not going to review or discuss all of them, but here are thoughts and recollections on, well, most of them.

Michael Benton reviewed his work on the changing fortunes of dicynodonts across the Permian Triassic Boundary (PTB). Much of this research will be familiar to you if you've read FrÃ¶bisch (2008) and Surkov & Benton (2008). Permian and Triassic dicynodonts occupied fairly different regions of morphospace, suggesting that they were quite different in terms of adaptations and so on, and that Permian-style dicyndonts failed to recover after the PTB. After the talk it only seemed appropriate to ask what Mike thought of the alleged Cretaceous dicynodont reported from Australia by Thulborn & Turner (2003). It seems that (just about) everyone is happy with its identification as a kannemeyeriiform (if I remember correctly, Tom Kemp stated that he'd examined it personally and was convinced by the identification): the question concerns its alleged Cretaceous date. Methinks we need isotope geochemistry or something to pin down its exact age, as has been suggested by others. While on the subject of anomodonts, the scansorial behaviour just proposed for Suminia by FrÃ¶bisch & Reisz (2009) was, needless to say, the talk of the town (figuratively) [adjacent Placerias reconstruction by Matt Celeskey of HMNH].

Adam Smith spoke about the 'Dragons' Dens' (for those not in the UK, I should note that there's a TV series called Dragons' Den): that is, the storage history of the marine reptile collection now kept at the National Museum of Ireland's Beggars Bush store. It's a pretty sorry tale of woeful neglect and mismanagement really, as the many specimens have been moved four times and kept from access for decades. The crown jewel of the collection - the amazing, articulated, near-complete holotype of Rhomaleosaurus cramptoni (casts of which can be seen at various institutions) - was, during the early 1960s, broken into bits with a sledgehammer when it had to be moved in a hurry. A new project on this specimen was initiated in 2004 (Arthur provided advice), and here lies the origin of Adam's Ph.D. work [Adam's world-famous R. cramptoni reconstruction shown here, borrowed from here on The Plesiosaur Directory].

Simon Carpenter discussed the many excellent finds he made in the Kimmeridge Clay at Westbury Quarry, Somerset. These included turtles, a spectacular pliosaur, and the holotype of the metriorhynchid Dakosaurus carpenteri. Unfortunately, the quarry is now closed, so no new discoveries! We also had talks from John Hudson on collecting trips in Scotland, and from Richard Edmonds on the Dorset Jurassic coast and on the problems of setting up a world-class collection centre in the area.

In view of Arthur's involvement with the world of African archosaurs, it seemed fitting that we had at least some archosaur-themed content, and this was fulfilled in the form of David Norman's talk on Heterodontosaurus. The many excellent illustrations demonstrate that the descriptive work on Heterodontosaurus is somewhere near completion [Heterodontosaurus cast shown here, from wikipedia]. Norman reviewed the discovery history of this unusual dinosaur, and also discussed its chewing behaviour. He argued that medial rotation of the mandibular rami was most likely, and hence that transverse grinding of some sort was occurring. Given that heterodontosaurids seem to be very basal within Ornithischia (Butler et al. 2008), it's perhaps surprising that a fairly complicated jaw mechanism was already present, and one that was apparently distinct from the pleurokinesis and propaliny present in later, more derived ornithischians. If you've been following the dinosaur literature you might be interested, as I was, to know what Norman thinks of Holliday & Witmer's (2009) contention that cranial kinesis was most likely absent in non-avian dinosaurs (this research was previously discussed here). Essentially, the response is that Holliday & Witmer didn't discount the possibility of cranial kinesis altogether (they merely discounted certain kinds of kinesis), and that tooth wear data provides compelling support for pleurokinesis and other complex forms of kinesis. I think there's a very interesting debate to be had here.

Mike A. Taylor and Jehane Melluish discussed the extremely interesting Thomas Hawkins, well known (in British vertebrate palaeontology) for acquiring good marine reptile fossils and for writing about them in (to our eyes) a bizarre style that combines scientific observation with a, shall we say, more colourful interpretation. As demonstrated by a number of feuds, disputes and legal cases, Hawkins was a bully and neighbour from hell (to use Mike's term); he seems to have gotten some of his money by marrying at least one rich woman.

Richard Forrest (and an absent Mark Evans) reported the latest developments on the Collard plesiosaur [shown in adjacent pic, and in image below]. This is the small, damn-near-complete, fully articulated juvenile plesiosaur discovered on the beach at Bridgwater Bay, Somerset, by Nick Collard in 2003: quite probably the most extraordinary plesiosaur specimen ever found. It's been CT-scanned and extensively x-rayed. It's probably a rhomaleosaur, and possibly similar to the animal called Plesiosaurus macrocephalus: as discussed here, this species is not part of Plesiosaurus at all, and its affinities and taxonomy remain unresolved.

The flipper tips of the Collard specimen are gently curved posteriorly, suggesting that this was the case in life, and a gap between the coracoids and gastralia might provide support for the presence of a cartilaginous sternum. One peculiarity is that some bones, while clearly visible with the naked eye, don't show up in the x-rays. Apparently, however, this is an artefact caused by pyrite content. The way the pelvis has collapsed indicates that it was originally quite deep... which of course brings us to the subject of plesiosaur body shape, a topic Tim Morris asked about in the comments a while ago. Plesiosaurs are a reasonably diverse bunch (well, within the constraints of a fairly conservative bauplan) and were not all alike. It seems that some (like cryptoclidids) were indeed fairly round in cross-section, while others (like some rhomaleosaurs) were far flatter, and wider than deep. I'm sure the many plesiosaurologists who visit Tet Zoo will provide additional thoughts in the comments. No pressure.

Academics in various disciplines are known to enjoy reconstructing their own 'academic lineages'. In any given field of research, it's often surprising how incestuous things have been, and on how influential one or a handful of individuals have been. Asking the question 'Is there a Cambridge School of Palaeontology?', Tom Kemp looked at Rex Parrington's academic 'descendants'. He tried to find synapomorphies and identified a clade. If you're part of this clade, rest assured that you were mentioned - and perhaps even pictured - somewhere during this presentation.

Our first day finished with Ryosuke Motani's public lecture 'Street's town symbol: the ichthyosaur two centuries since its discovery'. I suppose all I really need say is that Prof. Motani is clearly highly experienced at presenting a huge amount of technical information to a lay-audience in an understandable fashion. He covered his research on eyes, vision and deep-diving, the work on digit homology and flipper anatomy, and also showed how new work in China was ushering in a new phase in ichthyosaur research. It was a very impressive performance, and everyone seemed to enjoy it. On a technicality, one local lady told me that Street is not actually a town, but in fact a village (Europe's largest village, apparently). However, this was most certainly not Ryosuke's fault as we provided him with the title! [one of Chris Moore's ichthyosaurs shown in the adjacent image].

And that's the end of part 1: more in the following article.

For previous articles relevant to some of the material discussed here see...

Refs - -

Butler, R. J., Upchurch, P. & Norman, D. B. 2008. The phylogeny of the ornithischian dinosaurs. Journal of Systematic Palaeontology 6, 1-40.

FrÃ¶bisch, J. 2008. Global taxonomic diversity of anomodonts (Tetrapoda, Therapsida) and the terrestrial rock record across the Permian-Triassic Boundary. PLoS ONE 3(11): e3733. doi:10.1371/journal.pone.0003733

- . & Reisz, R. R. 2009. The Late Permian herbivore Suminia and the early evolution of arboreality in terrestrial vertebrate ecosystems. Proceedings of the Royal Society B doi: 10.1098/rspb.2009.0911

Holliday, C. M. & Witmer, L. M. 2008. Cranial kinesis in dinosaurs: intracranial joints, protractor muscles, and their significance for cranial evolution and function in diapsids. Journal of Vertebrate Paleontology 28, 1073-1088.

Surkov, M. V. & Benton, M. J. 2008. Head kinematics and feeding adaptations of the Permian and Triassic dicynodonts. Journal of Vertebrate Paleontology 28, 1120-1129.

Thulborn, T. & Turner, S. 2003. The last dicynodont: an Australian Cretaceous relict. Proceedings of the Royal Society of London B 270, 985-993.

tetrapodzoology Tue, 08/04/2009 - 06:57

Tags

Categories

Delightful introduction to the conference-looking forward
to the next installment. I am a little baffled by the
R. Cramptoni reconstruction-mainly by what looks
a row of 'floating' ribs along the lower line of the
belly.(I'm probably just mis-interpreting the image.)

Sounds fun! Will anyone be talking about mosasaurs, or this conference strictly sauropterygian (as far as marine reptiles)? And if that's the case, why aren't placodonts getting any love? :-)

A very intersting read. Sounds like a great conference :)

If you think it's confusing for Street to be a "village"... in New York State (and I presume some other US states), a "town" is an administrative area larger that can be larger than a "city". For example, the City of Ithaca (5 square miles) is surrounded by the Town of Ithaca (30 square miles). Plus, the administrative area of a "village" here, though smaller than a "town", can have several population centers within it.

"Given that heterodontosaurids seem to be very basal within Ornithischia (Butler et al. 2008), it's perhaps surprising that a fairly complicated jaw mechanism was already present, and one that was apparently distinct from the pleurokinesis and propaliny present in later, more derived ornithischians. If you've been following the dinosaur literature you might be interested, as I was, to know what Norman thinks of Holliday & Witmer's (2009) contention that cranial kinesis was most likely absent in non-avian dinosaurs (this research was previously discussed here). Essentially, the response is that Holliday & Witmer didn't discount the possibility of cranial kinesis altogether (they merely discounted certain kinds of kinesis), and that tooth wear data provides compelling support for pleurokinesis and other complex forms of kinesis. I think there's a very interesting debate to be had here."

One would have to wonder if the maxillary movements of pleurokinesis could be explained by mandibular rotation instead, something to think about. ;)

-Nick

Freaking Rhomaleosaurus! WE LOVE YOU DARREN

Also, one hopes Street would get into the ears of the Jim Henson company excetutives, Carrol Spinney's "Big Pliosaur" would only a be a heartbeat away.

Darren remember to save your money for ICVM in Uruguay, July 2010! Awesome conference!

Laura Porro, Norman's recent PhD student, is now recommended to become Dr. Porro after a viva with myself and Jeff Thomason last week, and her work answers the kinesis/jaw mechanism questions. I'll leave it to her to explain.

a cake with a historically significant plesiosaur on it

I know I've seen that fossil - or its cast - somewhere... Is it the Rhomaleosaurus/Thaumatosaurus victor holotype?

Asking the question 'Is there a Cambridge School of Palaeontology?', Tom Kemp looked at Rex Parrington's academic 'descendants'. He tried to find synapomorphies and identified a clade. If you're part of this clade, rest assured that you were mentioned - and perhaps even pictured - somewhere during this presentation.

Will this presentation turn into a publication? If not, who do I have to kill to get the ppt file?

what looks a row of 'floating' ribs along the lower line of the belly

are the gastralia, a series of bones in the belly wall that mammals, squamates and derived birds have lost, which is why you're not familiar with them.

There was only one possible choice for the cake decoration (and I should know as I chose it, though I did consider briefly an ATC glider for Arthur!): the classic Street plesiosaur Thalassiodracon hawkinsi (Owen, 1840) and specifically the holotype of the genus and species in the Natural History Museum, London. A very famous specimen used in all manner of books from Hawkins's own massive efforts (available online on Richard Forrest's website www.plesiosaur.com) through Buckland's Bridgwater Treatise ad nauseam.

The historically significant plesiosaur fossil on the cake is the holotype of Thallasiodracon hawkinsii. The original is in the Natural History Museum, London, BMNH 2018. It is well-known in part at least because of the large number of casts which were sold in the 19th century. They turn up in museums all over the world, usually misidentified as Plesiosaurus dolichodeirus due to misidentification in Ward's catalogue.

It was figured by that most eccentric of all fossil collectors (and there is **VERY** stiff competition), Thomas Hawkins (exceedingly unpleasant human being and possible serial killer according to Michael Taylor) in his "Memoirs of Ichthyosauri and Plesiosauri" as "Plesiosaurus tessarestarsostinus", and in "The Book of the Great Sea Dragons" as "Plesiosaurus triatarsostinus". We can be eternally grateful to Richard Owen, who renamed the taxon Plesiosaurus hawkinsi.

This specimen has recently been taken down from the wall for conservation, and Angela Milner reports that some elements have been reconstructed - not unusual for a Hawkins specimen. There will be considerable interest in developments.

It is well-known in part at least because of the large number of casts which were sold in the 19th century. They turn up in museums all over the world, usually misidentified as Plesiosaurus dolichodeirus

Ah, now I know why it looked so familiar; I've seen those misnamed casts. Thanks for the information, Mike and Richard!

exceedingly unpleasant human being and possible serial killer

Serial killer?! Blimey! Details, please!

Re: Thomas Hawkins, possible serial killer.
Mike Taylor gave us an account of what we know about Hawkins, and I think this will be published before too long. According to some records, he was married three or four times - something he thought not worth mentioning in his autobiography. It was known that he was on the lookout for wealthy women of marriageable age, but there seems to be a veil over what happened after his marriages. Given his character, which suggests that he suffered from an extreme personality disorder, a quiet disposal of his wives after he had his hands on their money seems not unlikely.

Richard: seriously? And I thought I was paying attention during Mike's talk...

Oh dear, my fur and whiskers. I'm glad Darren sand that as i don't recall it from my talk! I have a feeling this, rather, arose from something I wondered about aloud in the bar after my talk ... perhaps as the result of someone in the audience arguing that TH was a good guy, just misunderstood. If I recall rightly, I was talking about how the effect of revisiting a subject is often to revisit one's assumptions and impressions afresh, and joked that I was beginning to worry about the speed with which Wife No 1 disappeared - but then she was into her 60s if I recall rightly. Murder, serial or otherwise, is certainly not documented!! He was a serial perjurer, that's for sure. In any case we have only got one wife for sure, for all that local legend did say 3 or 4. See my Oxford Dictionary of National Biography article and a piece in the Somerset Proceedings in 2003 (vol 146 and no, sorry, I don't have pdfs of either) which cover some of what Jehane and I said.

David-thanks for the information. I guess I have some reading to do...not least on this Hawkins fellow. Can
anyone reccomend a good general text on his career? He
sounds a fascininating character. ( And whats the field
without a few skeletons in the closet, anyway?)

Craig:

And whats the field without a few skeletons in the closet, anyway?

Hmm. Leaving aside the possible case of Mr Hawkins, which are the worst actual crimes ever committed by professional paleontologists, anyway? (Baron Nopcsa's murder of his servant surely must feature highly on such a list.)

We might do well to shut down this thread right now. I wish I was joking, but an individual known to many of us in the Mesozoic reptile community was recently charged with the most serious of crimes.

Oh, sorry, I didn't know that. Delete my comment if you think it's inappropriate, Darren.

And/or mine as well, Darren. Apologies for the gaff.

the most serious of crimes

Plagiarism is not unknown even within the world of paleontology.

John wrote:

Darren remember to save your money for ICVM in Uruguay, July 2010! Awesome conference!

I'm gutted that I couldn't get to Avalon, but I'm saving up for Uruguay. Also, there's the Mosasaur 3 conference in Paris in May next year: http://www.plesiosaur.com/forum/index.php?topic=438.0

Laura Porro, Norman's recent PhD student, is now recommended to become Dr. Porro after a viva with myself and Jeff Thomason last week, and her work answers the kinesis/jaw mechanism questions. I'll leave it to her to explain.

Congratulations, Laura. I know her thesis includes some excellent work - looking forward to the papers.

It seems that some (like cryptoclidids) were indeed fairly round in cross-section, while others (like some rhomaleosaurs) were far flatter, and wider than deep. I'm sure the many plesiosaurologists who visit Tet Zoo will provide additional thoughts in the comments. No pressure.

Ok, I'll bite. Perhaps the very fact that you are mentioning the possibility of sternum in the Collard specimen earlier in that paragraph tells us how far we are away from understanding basic questions of body shape in plesiosaurs? On top of that, taphonomy overrides so much, and when comparing Liassic plesiosaurs with Middle Jurassic cryptoclidids you'd have to wonder how much the different taphonomic context affects what you're seeing.

One peculiarity is that some bones, while clearly visible with the naked eye, don't show up in the x-rays. Apparently, however, this is an artefact caused by pyrite content.

Interesting. The Kronosaurus specimen I CT scanned in my thesis had various sutures and cracks infilled with siderite, which showed up pretty clearly on the X-rays. The areas of bone which were hard to distinguish from the matrix seemed to have very similar mineralogy to the matrix (as I undertsand it, it's contrast in X-ray attenuation that is the major signal for showing structure in CT).

By coincidence, I had skimmed the Surkov and Benton paper the day before this post. There is apparently a significant difference between earlier (Permian, early Triassic) and later (late Triassic) Dicynodonts in skull proportions: all the later ones have comparatively high (as opposed to comparatively wide) occiputs. From which geometry suggests that the muscles for raising the head had greater mechanical advantage. From which the successive conclusions drawn were (i) late Dicynodonts tended to be high browsers (ii) so they lived in forests (iii) because this gave them a better chance of escaping from fast-moving archosaurian predators. Plausible, but it seemed to me that each step was more speculative than the preceding one.
--
Sounds like a fun conference. As a Synapsid/Theropsid chauvinist, I'm glad there was at least one talk that WASN'T about marine Sauropsids! (Grin!)

Baron Nopcsa's murder of his servant

Should probably be called a double suicide of him and his gayfriend. It's not clear (to me) if the latter gave informed consent, though...

It's usually stated that Bajazid Elma Doda's death was murder, but one biographical article (Elise 1999) merely said that Bajazid 'died with' Nopcsa. I always think it's unfortunate that Nopcsa's personal life has so often been of more interest than his scientific work. As Weishampel and Reif emphasised, he was no outsider or heterodox thinker in his own day, and contributed a lot. Then again, few of us aim to become King of Albania.

Oh, and I won't even mention that turtle.

Darren:

It's usually stated that Bajazid Elma Doda's death was murder, but one biographical article (Elise 1999) merely said that Bajazid 'died with' Nopcsa.

Indeed, those are the words used by the author* of this article. But surely Nopcsa's own words must count against the suggestion that there was some mutually agreed-upon suicide pact? In his suicide note, Nopcsa wrote that "I shot my longtime friend and secretary, Mr Bayazid Elmas Doda, in his sleep without his suspecting at all". That certianly sounds like a murder confession to me.

* Nitpick: the author's name is Elsie, not Elise.

That's the article I'd checked, thanks. So: Elsie, not Elise.

Thanks for reminding me I need to read that Weishampel and Reif piece. I did read somewhere, about ten years ago, that DW was working on a more complete biography of Nopcsa, but haven't followed up what was already published. I had to learn German just (mainly) to read Nopcsa's work on Cretaceous marine snakes for my PhD, so I invested pretty heavily in the guy not being a complete crackpot. And needless to say, I don't think he was...

He did some good solid work on dinosaurs, crocodiles, birds, varanoids and archaic snakes, which remains poorly known and is worth not only acknowledging but reading afresh to see what has been missed or ignored since. The same goes for his theoretical ideas in palaeobiology. There is supposed to have been animosity or resentment against him during his life, and there certainly seem to have been biases against him since, so that lack of citation is not hard to explain. E.g., Georg Haas was old enough to have met him, but Haas did not use his stuff even though he was certainly aware of it (mentioning without actually citing). Also, being multilingual, a large fraction of his work has never been directly available to monoglot scientists in any country.

...but there was this one scene that really needs to be in a film. As Director of the Geological Survey of Hungary, he hosted a meeting of the PalÃ¤ontologische Gesellschaft in Budapest in 1928 but was apparently mostly absent from the proceedings, being pushed into the hall in a wheelchair and giving a speech on the history of palaeobiology and his 'neo-Lamarckist' ideas on the role of disease-mimicking physiological adaptation in evolution. He included a couple of oblique references to his condition of (apparent) paralysis, but I don't know if anyone knows whether he was actually ill, injured or (I like this idea) experimenting on himself to study changes in his skeleton due to prolonged inactivity. I found a copy of the text in the Institut fÃ¼r PalÃ¤ontologie in Bonn, and part of it goes like this (in my trans., which doesn't seem to be up at the Polyglot Palaeontologist, maybe I forgot to post it):

I had planned for today a lecture on the ossification-delaying effect of aquatic life, but unfortunately I cannot at this time stand before you armed with the full scientific equipment, and I must therefore limit myself to bringing to your attention certain remarkable parallelisms between the skeletal changes of marine vertebrates and those terrestrial vertebrates which suffer from thyroid gland deficiency...

And then he goes a bit needlessly messianic at the end,

Gentlemen! With a weak hand have I tried today to draw aside a heavy curtain, to show you a new dawn. Pull more strongly on this curtain, particularly the younger ones among you; you will notice the morning light becoming ever stronger, and you will witness a sunrise.

It all seems a bit - oh, I don't know, operatic?

That same author, Robert Elsie, has also written an article about Nopcsa's 'secretary'/victim, Bajazid Elmaz Doda. Doda was, by the way, himself the author of at least one book* that was about rural life in - where else? - Albania.

* He finished the manuscript in 1914, but the book wasn't published until in 2007!

"It seems that some (like cryptoclidids) were indeed fairly round in cross-section, while others (like some rhomaleosaurs) were far flatter, and wider than deep. I'm sure the many plesiosaurologists who visit Tet Zoo will provide additional thoughts in the comments."

RE: cryptoclidids and body shape,

O'Keefe and Street (2009). Osteology of the Cryptocleidoid Plesiosaur Tatenectes laramiensis, with Comments on the Taxonomic Status of the Cimoliasauridae. JVP 29(1): 48-57.

Oh, and I won't even mention that turtle.

Kallokibotion bajazidi, apparently a stem-turtle...

The Adelaide Museum in South Australia had a Curator of Mammals in the nineteenth century who would have fitted in well with the gentlemen above. He would place letters inside his prepared exhibits detailing his hatred of seemingly every person he had professional dealings with. They are all still there, he did excellent work. As I recall museum staff take scrupulous care of everything he made, nobody wants to open anything up, and the letters may not be all that he put in there. Also he had a shed out the back of the Museum where he boiled down specimens, and every so often came to the door with a handgun and blazed away at all the local stray dogs congregating there. I will see if I can find his name.
Darren, thanks for the blog. It is the most interesting thing I read these days.

I'm genuinely disappointed to have not been able to have attended the meeting, both because of the subject matter, and in being another of Arthur's academic nephews.
Anyway, I'm back now, so I'll bite too...
Plesiosaur body shape is tricky to reconstruct as they do tend to get flattened. As Daren says, they were reasonably deiverse, within a conservative bauplan, so what seems to be the case for one shouldn't apply to all. The best evidence of a deep bodied plesiosaur, IMHO, is Peloneustes, in which the coracoids seem to have made an angle of roughly 90 degrees (or so) with one another at the midline. However, in others it's more a case of trying to articulate distorted ribs and transverse processes together. That said, an animal with widely projecting lateral cornua on the posterior ends of the coracoids (eg Cryptoclidus) would seem to demand a wider body shape than one without.

Lysorophians and aÃ¯stopods

tetrapodzoology — Sun, 21 Jun 2009 05:33:00 +0000

Lysorophians and aÃ¯stopods

At some stage, I'll have to write full-length articles on lysorophians, aÃ¯stopods, the remaining temnospondyls, nectrideans, microsaurs, and assorted other groups of Palaeozoic and Mesozoic non-amniote tetrapods. Alas, this hasn't happened yet. In the meantime, here are some slides from one of my talks...

Lysorophians are peculiar, long-bodied lepospondyls from the Carboniferous and Permian, best known for Brachydectes. They had strongly reduced limbs and limb girdles and elongate skulls, typically with a strongly emarginated cheek region. Trace fossils suggest that some species were aquatic sidewinders (Braddy et al. 2003), and others seem to have aestivated at the bottom of burrows (Olson 1971). Lysorophians have been regarded by some authors as derived nectrideans allied to aÃ¯stopods, but others find them outside of a clade that includes nectrideans, aÃ¯stopods and others (Ruta et al. 2003)... sorry if all of these terms are new, but you at least know one nectridean as it's featured in every single book ever on prehistoric animals: boomerang-headed Diplocaulus.

As for aÃ¯stopods, these are also long-bodied Carboniferous and Permian animals, imagined by some to be eel-like swimmers, and by others to be terrestrial and fossorial (the slide above says that they included both aquatic and terrestrial forms, but I'm not sure where I got that from. Has this issue been resolved yet?). Limbless and snake-like, they reduced and lost various of their skull bones over time, and some workers have suggested that they exhibited snake-like cranial kineticism (though this has been contested). So much more to say, of course.

For previous articles on Palaeozoic non-amniotes see...

They are, clearly, horribly under-represented so far.

PS (added 22-6-2009): here is something I thought I'd never see. Wow, maybe people do love Palaeozoic non-amniote tetrapods after all...

Refs - -

Braddy, S. J., Morrissey, L. B. & Yates, A. M. 2003. Amphibian swimming traces from the Lower Permian of southern New Mexico. Palaeontology 46, 671-683.

Olson E. C. 1971. A skeleton of Lysorophus tricarinatus (Amphibia: Lepospondyli) from the Hennessey Formation (Permian) of Oklahoma. Journal of Paleontology 45, 443-449.

Ruta, M., Coates, M. I. & Quicke, D. L. J. 2003. Early tetrapod relationships revisited. Biological Reviews 78, 251-345.

tetrapodzoology Sun, 06/21/2009 - 01:33

Tags

herpetology

Palaeozoic tetrapods

Categories

Life Sciences

:-) :-) :-)
*happy happy joy joy*

Aquatic sidewinders? Why would an aquatic animal sidewind?

I don't remember which paper it is that debunks the hypothesis of the kinetic phlegethontiid skull, but it looked very convincing. In general, I suspect most non-mammal tetrapod palaeontologists started out by learning extant squamate anatomy and are therefore accustomed to see lots of mobile joints in every skull, leading to streptostylic gorgonopsians, mesokinetic Archaeopteryx, sort of pleurokinetic anthracosaurs, and of course pleurokinetic ornithopods...

As for aÃ¯stopods, these are also long-bodied Carboniferous and Permian animals, imagined by some to be eel-like swimmers, and by others to be terrestrial and fossorial (the slide above says that they included both aquatic and terrestrial forms, but I'm not sure where I got that from. Has this issue been resolved yet?).

Based on things like the circular cross-section of the body, Germain (2008a, b) argues for a terrestrial lifestyle for all aÃ¯stopods and even suggests that Lethiscus could be the oldest known terrestrial tetrapod, complete with the pun "the first step on land -- without legs".

BTW, you remember how Ruta & Coates (2007) found the adelogyrinids next to the colosteids and far, far away from the other "lepospondyls"? Looks completely crazy at first glance, but it's apparently correct. At least two papers on this are in the works.

Germain D (2008a): Anatomie des LÃ©pospondyles et origine des Lissamphibiens [PhD thesis, partially in English]. Paris: MusÃ©um National d'Histoire Naturelle. 351 pp.
Germain D (2008a): A new phlegethontiid specimen (Lepospondyli, Aistopoda) from the Late Carboniferous of Montceau-les-Mines (SaÃ´ne-et-Loire, France). Geodiversitas 30: 669 -- 680.
Ruta M, Coates MI (2007): Dates, nodes and character conflict: addressing the lissamphibian origin problem. Journal of Systematic Palaeontology 5: 69 -- 122.

I'm sorry, I' not familiarised with these groups... but if they were fossorials.... shouldnt they at least retain, if not reinforse, their skull bone (particulary the skull roof and the postorbital bar)??

It is impossible to have too many posts about pre-Permian tetrapods.

It is also impossible to have too many pre-Permian tetrapod fossils.

It is also impossible to form a consensus on the relationships between many of the various groups. The morphological gaps are impressive. E.g. whence aÃ¯stopods?
Heck, whence "lepospondyls"? [And my personal favorite: whence Acherontiscus?] Lotsa luck forming an authoritative answer. If the creationists ever bothered to read the literature, they would have a field day with the gaps.

I harmonize with Davids sentiments, thanks for the post Darren.

Many thanks for comments, David in particular (I was unaware of Germain's work).

For those who've been following, Tet Zoo did not make it into the top 3 in the 3 Quarks Daily competition. Oh well. Making it into the top seven was an achievement in itself, thanks to all who voted.

WHAT???!!!???!!! Tet Zoo didn't make it into the top 3? That's disgusting. It should have won! BTW, I love those little eely-fishy-amphibiany critters. There so cute! (And, I must admit, I'd never even heard of most of them before. Shocking, I know.) When will you write a full-length article about them?

Derren: I refuse to turn this discussion into one on dinosaurs (I personally can't get enough dinosaurs, but we also can't forget about all the other cool creatures out there, including these little things in the current post. After all, this is Tet Zoo, not Dinosaur Zoo, and one major reason I come here is for the variety). However, there is something I would like to know. As you outlined in Troodontids and Owls - Oh the Irony!, trodontids are very owl-like. Thus my question: Could troodonts turn their heads nearly all the way around, like owls can? I know it's a very idiotic question, but please answer it if you can. Thank you!

I'm really glad to see this post, aÃ¯stopods are really interesting, especially from an evo-devo perspective. The trunk vertebral count is pretty well known to be genetically controlled and strict in some amniote groups, and it's interesting to see where it is flexible in other.

I'm also glad this is a non-dinosaur post.... the number of comments to this one, in comparison to comments on dinosaur posts, it noticeable. I understand the enthusiasm for dinosaurs, but what about all the other tetrapods readers? Dinosaurs are even more interesting in the context of how they fit as tetrapods, but one cannot see that if they ignore the rest.

It reminds me of marine mammal work - I could publish a million papers about Sirenia and Desmostylia, but the only time anyone notices marine mammals is when they are whales or pinnipeds. It almost makes we want to avoid working on whales, except that being so diverse they are great for exploring in a comparative way.

I wonder if that's a subject for another post or blog, the question of what motivates people's interest in specific fossil groups?

I hate to sound overly speculative, but I'd hazard a guess ... er.. opinion... that these beauties did NOT have feathers. Anyone care to challenge me on that? ~

BTW, Darren, more marine/aquatics always appreciated; I note that your 'clustermaps' shows red like crazy but still lots of blue showing! Oh, and, do you think any of these ancient slitherers were electroshocking predators?

I've got a question for Darren (Comment 6). Does anybody know when he usually checks the comments on his articles?

Interesting creatures! Me too, never heard of them before.

BTW - did extinct amphibians have tadpoles (I know, some were neotenic). Do tadoples fossilize? Does a tadpole have a cartillage skeleton - and what happens to it when it metamorphoses?

Jerzy: Yes, tadpoles fossilize, but only rarely. Tadpoles do, indeed, have a cartillage skeleton, which is then replaced with a bony one when they metamorphose.

We find snakes and snake like animals among the reptiles and amphibians and their ancestors, but no snake like animals among the mammals and their ancestors. What is this telling us?

What it tells me is that the ophidiform body plan was lost among the ancestors of mammals fairly soon after reptiles and mammals split, and thus the reptilian and mammalian lines go back a lot further than we think.

Now consider the difference in the placement of the pineal gland in mammals and reptiles.

I'd never heard of any sidewinding trace fossils, amazing to see. But there's absolutely no way they were made underwater; any animal able to sidewind would more easily swim by simple lateral undulation, with no twisting required. The lifting of the body loops in sidewinding is a way of concentrating contact forces at a small proportion of belly area, increasing friction to prevent sliding, so it would be totally pointless where body weight is supported (and locomotion facilitated) by water. Even with a very thin water layer over the mud there'd probably be a lot more lateral and posterior sliding, not such clear straight tracks, so I guess the mud was drained enough to be sticky rather than slippery. I'll go look up the paper now...

Oh, and Michael Erickson, some of your comments on the preceding post reminded me of this. You Americans!

Alan Kellogg: What is this telling us? That for small endothermic animals, surface area / volume ratios matter? But what it tells you is... very strange. The ophidiform body plan was lost among ancestors of mammals (lost? - but they never had it!) - maybe you mean potential for the ophidiform body plan? (BTW, we'd usually say serpentiform, so as not to mix Latin and Greek roots). But what has this got to do with divergence dates or pineal organs?

John Scanlon, #13

No snake like mammals: Exactly? And how long ago was the shape lost? How far back does one have to go until one finds an ancestor of mammals that was snake like?

On pineal glands: Two questions;

One. Where is the pineal gland located in reptiles?

Two; Where is the pineal gland located in mammals?

Yes, it's located in the brain in both cases, but where exactly in the brain?

Re: "underwater" sidewinding.
The trace fossil sure LOOKS like a trace of sidewinding, and it may be (I wouldn't know) that there are good sedimentological reasons to think the substrate was wet when the sidewinder wound it, but how deep: perhaps sidewinding was used for essentially above-water progression (hence obviating the "why didn't they just SWIM?" objection) when there was only a millimeter of water over the substrate?

Ancestor of mammals that was snakelike?

Well, that would not be any synapsid, amniote, tetrapod, osteichthyan or gnathostome. Basically, some kind of chordate 'worm', say the last common ancestor of mammals and lancelets or conodonts. Precambrian or early Cambrian, say.

@Darren: I dunno if this entry has anything to do with my recent begging for entries on aÃ¯stopods, but either way you have my gratitude.

@Alan: The mammal-"reptile" split is currently thought to have occured in the Carboniferous, 6/7 or so the way back to Acanthostega. How much earlier would you have it?

Of course, depending on how you define "ophidiform", Basilosaurus may qualify.

Jerzy:

Do tadpoles fossilize?

Sometimes, yes. See here, for example.

I'm here, just very busy (so much so that I've again been unable to complete anything new for the blog). Assorted responses...

-- troodontid neck flexibility (comment 6). I don't think anyone has published any comments on deinonychosaur neck flexibility, but given the anatomy of the cervical vertebrae and length of the neck, I'd expect that these animals could turn their heads well round to the side. However, their cervicals were long, and low in number compared to neornithines like owls (where the cervicals are far shorter and apparently with a greater degree of rotational ability). In other words, no reason to imagine owl-like neck flexibility.

-- Brian (comment 7): I love dinosaurs, but I get frustrated by the fact that they sometimes seem to be the only animals that draw in a huge readership. Note how few comments appear when I post about certain groups of living animals: very frustrating, but nothing I can do about it. Also of great interest is the fact that the super-sexy animals â dinosaurs (including birds), hominids â are the only ones that draw in huge amounts of vocal controversy and 'fringe' interest. This is really ironic, as the greatest controversies and areas of uncertainty in evolutionary biology do NOT concern such things as bird origins, or the environmental preferences of early humans, but such things as microsaurs and lissamphibian origins, and the position of snakes and turtles.

-- Did any Palaeozoic/Mesozoic non-amniote tetrapods have aquatic larvae (comment 10)? Note for starters that the term 'tadpoles' is restricted to anurans: the larvae of other animals (including other lissamphibians) should not be called tadpoles (or so I'm reliably informed). We know that some temnospondyls and perhaps some microsaurs, at least, had aquatic larvae and underwent metamorphosis, but the transformations involved may have been less radical than that associated with anurans, and it may be that 'advanced' temnospondyls â like eryopoids, dissorophoids and zatrachydids â and just a few microsaurs (like Pantylus) were the only ones that did this (Schoch 2001). How widespread were larval phases and metamorphosis among tetrapods in general? Though some authors have opined that loss of the larval stage was unique to amniotes (Robert Carroll said this in a few papers from the 1970s and 80s), I get the impression that those tetrapods more basal than temnospondyls and microsaurs (Ichthyostega and similar forms, baphetids, anthracosaurs, nectrideans, lysorophians etc.) did not undergo a profound ontogenetic transformation. A few people who work on these groups are Tet Zoo regulars: they may know more!

-- Sidewinding tracks preserved underwater (comments 13): obviously, you need to read Braddy et al. (2003), the relevant section is on pp. 678-680. They argue that the tracks were indeed produced underwater, and they conclude that the long-bodied animal that made the tracks was indeed undergoing a sort of subaqueous sidewinding. There is another reason to be slightly sceptical: the diagrams (p. 679) show the foot impressions much more clearly than do the trace fossils themselves (p. 678), and the foot impressions are the important bit, as they indicate that these traces were not made by fish (fish often leave S-shaped traces on submerged substrates). However, the authors are pretty convinced about the foot impressions, and are therefore pretty confident that the tracks were made by a long-bodied tetrapod. One of the authors on the paper is also a Tet Zoo regular: does he have comments?

And, Andreas, yes, you were inspirational :)

Right, back to work (TV research)...

Ref - -

Schoch, R. R. 2001. Can metamorphosis be recognised in Palaeozoic amphibians? Neues Jahrbuch fÃ¼r Geologie und PalÃ¤ontologie, Abhandlungen 220, 335-367.

Thanks, fascinating.

Even more interesting are developmental/genetic implications of tadpole. Vertebrate which radically alters its body plan, huge areas of bones, muscles and nerve structures disappear and develop. I wonder why half of genetic papers on cancer, hox genes etc. don't draw heavily from amphibian development.

PS. snakelike mammals? Look at weasels and ground squirrels at land, and otters and whales underwater.

> BTW - did extinct amphibians have tadpoles (I know, some
> were neotenic).

Jerzy,
some non-amniote tetrapods had distinct juvenile and adult forms. Others dropped the adult form and became neotenic. Others dropped the juvenile forms and became peramorphic.
This is one of the reasons why non-amniote tetrapod systematics are such a mess. To quote Palaeos: "Like some peculiar non-Euclidian fold in the universe of physics, this is a region in which the fundamental laws of cladistics may not hold.(...) How can we do good cladistics on animals which may have more than one morph?" Or, even worse, with animals that are known from only one of the two potential morphs? The microsaurs, for example, had effectively jettisoned the adult form. If an adult form of, let's say, *Pantylus*, had existed, it might have looked exactly like an early amniote, and the phylogenetic position of this beast may change entirely. This is, btw, one of the reason why stem tetrapods shouldnÂ´t be called "amphibians", we don't know for sure if temnospondyls or lepospondyls were actually closer related to modern lissamphibians than they are to amniotes.

> Do tadpoles fossilize?

We have fossils of juvenile seymouriamorphs, and some neotenic temnospondyls are so abundant that the remains of their armour are used as index fossils, but those aren't "tadpoles" in the strictest sense.

Darren:

Note for starters that the term 'tadpoles' is restricted to anurans: the larvae of other animals (including other lissamphibians) should not be called tadpoles

That I didn't know. What should the larvae of salamanders and newts be called, then? Just 'larvae'?

Note how few comments appear when I post about certain groups of living animals: very frustrating, but nothing I can do about it. Also of great interest is the fact that the super-sexy animals â dinosaurs (including birds), hominids â are the only ones that draw in huge amounts of vocal controversy and 'fringe' interest.

Cryptozoology also attracts the crowds, no? (Personally, though, I rather prefer the more favourable signal-to-noise ratios in the less 'sexy' subject threads.)

if they were fossorials.... shouldnt they at least retain, if not reinforse, their skull bone (particulary the skull roof and the postorbital bar)??

Sure, but the lysorophians only burrowed into soft mud at the bottom of bodies of water (like lungfish), and the aÃ¯stopods burrowed, if at all, in leaf litter. And while Phlegethontia has indeed lost the parietals, it has a complete ossified braincase roof.

It is also impossible to form a consensus on the relationships between many of the various groups.

Naaah. We're close to having one. :-)

The morphological gaps are impressive. E.g. whence aÃ¯stopods?

Probably from the nectrideans (which are paraphyletic in this case) or right next to them.

Heck, whence "lepospondyls"?

Lepospondyls, amniotes + diadectomorphs, seymouriamorphs, and Solenodonsaurus are all very similar. Westlothiana, the basalmost lepospondyl, was originally thought to be an amniote or very close to them.

And my personal favorite: whence Acherontiscus?

It goes right between colosteids and adelogyrinids, where Ruta & Coates (2007) found it.

Yes, it's located in the brain in both cases, but where exactly in the brain?

In the exact same place. What you're talking about is the fact that the mammalian cerebral hemispheres are so bloated they've overgrown the pineal gland.

Tadpoles: later. I have to go. (Translation: I should have gone 1/4 h ago...)

What should the larvae of salamanders and newts be called, then? Just 'larvae'?

Yes. "Tadpole" is reserved for the stage before the extremely compressed metamorphosis of frogs.

How could I be so rude as to ignore a personal request for comment?
My involvement in the project came about when I was at Bristol and Simon Braddy asked me if there were any long-bodied limb-reduced tetrapods in the Permian. I then told him of Lysorophians. When he showed me pictures of the tracks I immediately said - 'they look like sidewinding tracks'. That was pretty much my input into the paper. To be sure I'd never been quite convinced that they really were footprints on those tracks but they certainly do contain are a series of repeating en-echelon marks that look like sidewinding. If they weren't sidewinding I don't know what the hell those trackmakes were up to.
As an interesting aside, similar marks have since been found in the Clarens Formation by Francois Durand of the University of Johannesburg. Now this is a nice aeolian unit - a perfect environment for sidewinding as we know it but of course being Early Jurassic - no snakes to sidewind. Francois thinks that snakes are an older clade than their body fossil record would suggest, he actually goes so far as to ascribe the Clarens traces to the activities of advanced viperids. Needless to say that idea is not terribly popular but the question still remains what long bodied animal was around to make those tracks? - none that I know of.
Which then begs the question 'Is there some other action that we are not thinking of that can produce a sidewinder like trace?' I really don't know.

I was thinking about the "no mammalian snakes" post. I don't know a whole lot about the details of the vertebrate skeleton, but it seems to me that mammalian backbones are better able to bend vertically, while snakes, amphisbeanians, caecelians, and all these other things have vertebral columns which bend horizontally. Just compare the up and down tailstrokes of a whale with the side to side strokes of everything else. So a mammal just wouldn't be able to slither effectively-it just wouldn't bend well in the right way. Or at least that's my theory. This is supported by the fact that there is a fairly snakelike fossil whale (the name escapes me at the moment). In the water the direction of undulation doesn't really matter.

@Adam: You're presumably thinking of Basilosaurus which I mentioned above.

I did a double-take when I saw Adam Yates say...

I don't know a whole lot about the details of the vertebrate skeleton

Let me note that the Adam in comment 26 is not the same as the Adam in comment 25. The latter is Adam Yates, author of Dracovenator (both the blog and the taxon :)).

Oh, and, as David said, salamander larvae should indeed just be called larvae. However, the name 'eft' is also available (though little used).

Darren:

'Note how few comments appear when I post about certain groups of living animals: very frustrating, but nothing I can do about it.'

Well, sometimes we just read with amazement! It's not that these topics are uninteresting. Topics which generate most comments are usualy not the most interesting - there are some troll topics which generate vomitingly repetitive arguments. Please keep the unusual animals coming!

Thanks!

So, how a skeleton of a larval non-anuran looks like? Is it carillage? Does it have all the bones of an adult + gill arches?

To all, check the article anew: have just added an update.

For those who are interested I've put up a post on the poorly known Clarens side-winding trace up on Dracovenator.

"I don't know a whole lot about the details of the vertebrate skeleton"

After a slew of rejections from journals I'm wondering whether or not that might be true.

230-250 vertebrae? Amazing! I'm guessing the skeletons in the first picture are not to scale with each other? How large did these guys get?

Quick question, which will lay my ignorance bare: how exactly would such a large number of vertebrae have formed? I am guessing that these guys are in some way descended from tetrapods possessing fewer vertebrae; thus, how do you add a vertebra to the vertebral column? I know in humans, at least, extra vertebrae can be present as a result of genetic mutations: is the situation in these amazing lysorophians and aÃ¯stopods just the result of selective pressures favouring such mutations over time, or is there some other way for vertebrae to be "added"?

I'm back (at home now) and I'm looking at the Braddy, Morrissey and Yates paper. There are a couple of issues to comment on: (1) subaqueous vs. terrestrial, and (2) direction of motion. This leads to (3) questioning taxonomic affinity of the trackmaker. Disclaimer: IANA ichnologist, but I do see plenty of reptile tracks about these parts of northern Australia, and I've done a small study of sidewinding in elapids.

(1) I gave reasons above (comment 13) why sidewinding underwater would make no sense. Numerous aquatic snakes sidewind on wet mud or sand, but as far as I'm aware nobody ever reported seeing it done underwater. After a closer look at the figure of Serpentichnus robledoensis (fig. 4, reproduced by Darren above) I now see more evidence of lateral sliding, and the sediment is apparently a very fine-grained mud because those things are tiny, each body impression of the bigger trackway about 88 mm long. So I still think they're subaerial, but the top layer of the substrate was wet and very soft and slippery, not 'sticky' as I judged when guessing a larger body size (30 cm or more). The authors infer that the trackways were "produced in a subaqueous freshwater environment, with intermittent subaerial exposure"; the parallel lineations attributed to a water current are much fainter than the animal tracks but seem to overlie them, and I don't see why they couldn't all have been formed as water rose to very gently cover the tracks.

(2) When a snake sidewinds, waves are initiated by lateral (and posterior) motion of the (usually raised) head end, and travel from front to back (caudad) as in normal lateral undulation. Supposing a starting position with the body at rest, stretched out straight on a nearly frictionless surface: the only possible motions involve pulling one or both the extremities towards the centre of mass. That's what happens: the head (or most anterior part touching the ground) is lifted, pulled back and to one side, and replaced on the substrate. The lateral component causes compression ridges along the side the snake is travelling away from, as it pushes loops in the opposite direction. The rest of the body follows, naturally, and by the time the tail is lifting off the head may already be two full steps away, or more.

But what Braddy et al. depict in fig. 5 requires loops to form at the tail and travel craniad (each lifting cycle moving body segments forward and to the left). This arse-about progress is biomechanically possible, but seems behaviourally unlikely as a normal means of locomotion. However, it does seem consistent with the sliding traces being mainly on the left side (especially in the posterior trunk), with compression ridges to the right... UNLESS
(3) the 'forward-facing pes prints' are actually marks of backward-facing pectoral fins. The supposed drag-marks of 'ventral scales' could also be from fins - they look more like they were produced by a row of spines than scale-margins.

So that's my version: a sidewinder indeed, but not a subaqueous serpentiform tetrapod moving head-forward and to the left (up-slab in Braddy et al's fig 4), rather a subaerial anguilliform fish moving back and to the right (still up-slab, but head-down). Arguments, any?

BTW Darren, what's that coiled skeleton in the photo next to the trackways in the slide? Was that from Carroll '88? (looks familiar but I don't have a copy)

Is there a difference between serpentiform and anguilliform, or is it just the later seems more natural when applied to fish?

Braddy et al. (2003) is a strange paper. What are xiphosurans doing in a freshwater environment, there are nectrideans with just four fingers per hand, I can't see the pes prints of Serpentichnus, what sense does it make to assume sauropsid scales on a lysorophianâ¦

As an interesting aside, similar marks have since been found in the Clarens Formation by Francois Durand of the University of Johannesburg. Now this is a nice aeolian unit - a perfect environment for sidewinding as we know it but of course being Early Jurassic - no snakes to sidewind.

Hm. All I can suggest is Eocaecilia, but of course a sidewinding caecilian would be bizarre enough in itselfâ¦ Eocaecilia does come from an aeolian deposit, though.

I get the impression that those tetrapods more basal than temnospondyls and microsaurs (Ichthyostega and similar forms, baphetids, anthracosaurs, nectrideans, lysorophians etc.) did not undergo a profound ontogenetic transformation.

Apparently all those animals, and most temnospondyls, underwent a very slow transformation. You could define metamorphosis by the point at which the gills disappear* and/or the gill slits close** (and that's done in the seymouriamorph literature), but none of the other changes happen at the same time: one bone ossifies after another, and the body proportions change gradually.

The dissorophoid temnospondyls, as well as the zatrachydid (â¦zatracheid?) ones, concentrated many of these changes, and many new ones, in a shorter period that can be called metamorphosis. (In addition to Schoch 2001, see Schoch 2002, ref below.) This involves the delay of some changes (like the ossification of quadrate and articular) until metamorphosis, a condition that reaches an extreme in the micromelerpetontids and the branchiosaurids (some species of which, perhaps most, were neotenic).

Salamanders and caecilians have an even more clearly defined metamorphosis (which, in salamanders, involves major restructurings of the bones of the palate, like the complete loss of the palatine for example, as well as general bone remodelling), and the frogs show the extreme condition by making sexual maturity, loss of the tail, lots of ossification, and other events part of the package (so much so that even completely aquatic frogs like pipids undergo a complete metamorphosis with the loss of tail, gills, and gill slits).

Lepospondyl ontogeny is completely unknown, except for partial growth series in the neotenic "microsaurs" Microbrachis and Hyloplesion (where even the smallest known specimens have a completely ossified skull and even a completely ossified vertebral column), eight specimens of Phlegethontia which can be grouped into three stages of a growth series (Anderson 2002), and traces of what appears, by comparison to lissamphibians and/or temnospondyls but not Phlegethontia, to be neoteny in lysorophians (lack of certain skull bones, lack of interpterygoid vacuities, retention of sutures between centrum and neural arches and even between left and right neural arches). That's it. To add insult to injury, the skull ossification sequence (as far as it can be reconstructed from those three stages) is utterly unlike those of temnospondyls, lissamphibians, or anything else.

Schoch (2001) says the lepospondyl Pantylus had a slow ontogeny not condensed into a metamorphosis. Neither I nor Michel Laurin (pers. comm. -- he's sitting at the other side of the desk) are aware of any kind of known growth series for Pantylus, and Schoch doesn't cite anything for this. ~:-| I'll write to him.

* There's evidence for gills in apparent adults of the temnospondyls Trimerorhachis, Dvinosaurus, and Gerrothorax, BTW. But these have long been considered completely aquatic and even neotenic.
** In salamanders with incomplete metamorphosis, like cryptobranchids and Amphiuma, the gills disappear, but the gill slits never close -- they're useful for feeding.

On to tadpoles. Tadpoles are basically pharyngula-stage embryos elaborated into a feeding stage; that's why they're so similar to tunicate larvae. The entire skeleton is cartilaginous for a long time (some dermal skull bones appear a bit before metamorphosis); there are no real jaws and no teeth; the tail never ossifies at all. Many tadpoles are herbivorous, while no adult frog is.

Jason S. Anderson (2002): Revision of the aÃ¯stopod genus Phlegethontia (Tetrapoda: Lepospondyli). Journal of Paleontology 76: 1029 -- 1046.
Rainer R. Schoch (2002): The evolution of metamorphosis in temnospondyls, Lethaia 35: 309 -- 327.

Many neat comments and questions here - I don't have time to address them though.

What is the coiled skeleton shown on the slide (comment 34)? It's a skeleton of Brachydectes elongatus (originally described by Olson (1971) as Lysoropus tricarinatus), apparently aestivating at the bottom of a burrow (taxonomic revision provided by Wellstead (1991)).

Refs - -

Olson, E. C. 1971. A skeleton of Lysorophus tricarinatus (Amphibia: Lepospondyli) from the Hennessey Formation (Permian) of Oklahoma. Journal of Paleontology 45, 443-449.

Wellstead, C. F. 1991. Taxonomic revision of the Lysorophia, Permo-Carboniferous lepospondyl amphibians. Bulletin of the American Museum of Natural History 209, 1-90.

Failed to close a <b> tag somewhere near the end of comment 36.

So that's my version: a sidewinder indeed, but not a subaqueous serpentiform tetrapod moving head-forward and to the left (up-slab in Braddy et al's fig 4), rather a subaerial anguilliform fish moving back and to the right (still up-slab, but head-down). Arguments, any?

Fascinating.

What could such a "fish" be? Acanthodes? A baby of one of the more elongate chondrichthyans like Thrinacoselache?

some non-amniote tetrapods had distinct juvenile and adult forms. Others dropped the adult form and became neotenic. Others dropped the juvenile forms and became peramorphic.

Lack of a terrestrial adult morph appears to be plesiomorphic for limbed vertebrates (Schoch 2001).

This is one of the reasons why non-amniote tetrapod systematics are such a mess.

A mess? The only real problem is where the lissamphibians fit. (This particular problem is connected to ontogeny discombobulating phylogeny, though.)

To quote Palaeos: "Like some peculiar non-Euclidian fold in the universe of physics, this is a region in which the fundamental laws of cladistics may not hold.(...)

At least one of the authors of Palaeos.com loves his scenario-based phylogenies so much that he spent a lot of time and webspace on saying "Haaa! I found a hole in cladistics!!!1!" It gets annoying after a while.

How can we do good cladistics on animals which may have more than one morph?" Or, even worse, with animals that are known from only one of the two potential morphs?

Easy: score only adults as known for ontogeny-related characters. See Wiens et al. (2005).

The microsaurs, for example, had effectively jettisoned the adult form.

What??? Do you mean Microbrachis, or do you maybe mean the branchiosaurid and micromelerpetontid temnospondyls?

If an adult form of, let's say, *Pantylus*, had existed,

Pantylus is only known from terrestrial adults (unless Schoch's unsourced claim cited above is right -- as mentioned, I'll write to him).

it might have looked exactly like an early amniote, and the phylogenetic position of this beast may change entirely.

Yeah, right. It might have grown a fifth finger on the already fully ossified hand, a transverse flange on the pterygoid, a fucking supratemporal in the skull, a drastically more plesiomorphic skull-atlas joint, an axis intercentrumâ¦ Look, this is nonsense. I mean, I can't disprove it, but it fails epically at resisting Ockham's Chainsaw.

Wiens JJ, Bonett RM, Chippindale PT (2005): Ontogeny discombobulates phylogeny: paedomorphosis and higher-level salamander relationships, Systematic Biology 54: 91 -- 110.

I always see microsaurs and eel-amphibians briefly described in every "encyclopedia of prehistoric life" type book I read, but there's never enough information on them. Good to read this post, and the ensuing comments.

Steve P @ #33 asked a good question (from the perspective of a developmental biologist at least):

how exactly would such a large number of vertebrae have formed?

Vertebrae develop from embryonic cell populations called somites (the sclerotome part, to be specific), or chunks/balls of mesoderm on either side of the neural tube. The somites themselves are periodically segregated (in pairs) from masses of presomitic mesoderm through a "clock and wavefront" mechanism, driven by a molecular oscillator.

There's an interesting paper by Gomez et al. in Nature, from 2007 (doi:10.1038/nature07020) on somitogenesis in the corn snake embryo, which concludes that the segmentation "clock" in the mesoderm runs faster in this animal, with respect to overall developmental rate. They propose that this leads to the formation of more somite pairs (and hence more vertebrae) in the snake, but the individual somites are much smaller. The corn snake embryo has 315 somite pairs, and the images in the Gomez paper are absolutely fascinating. The paper includes comparisons with somitogenesis in zebrafish, mouse, and chick embryos, and I guess one could extrapolate to the lysorophians and aistopods discussed here.

I just saw the add-on. Yes, I, for one, LOVE Palaeozoic non-amniote tetrapods! Keep 'em coming Darren!

Only one who has never been in thrall to crosswords would say that the word "eft" is rarely used. It's such a pleasing word that it's disappointing that most people rarely find occasion to use it in conversation. I try, I try.

I hate crosswords. Also soduku, sport, cookery programmes and reality TV.

Cheers Barn Owl, I will read that paper (and another associated one I found whilst searching for Gomez et al.) on my lunch break!
#43: Darren, I whole-heartedly agree with you about cooking programs and (especially) "reality" TV shows, though I love soccer (sorry, football; force of habit)...

[aÃ¯stopods] Probably from the nectrideans...

How "probably"? Skulls are kinda quite different. Same for caudals. From stem to stern.

Lepospondyls, amniotes + diadectomorphs, seymouriamorphs, and Solenodonsaurus are all very similar.

Mmm, yes, aÃ¯stopods, Diadectes, easily confused. :-)

[Acherontiscus]...goes right between colosteids and adelogyrinids, where Ruta & Coates (2007) found it.

*fnort*

I haven't seen Ruta & Coates (2007), does it differ much from Ruta et al. (2003)?

The only real problem is where the lissamphibians fit.

Assuming monophyly for the group. Could be two or three problems. Besides, lissamphibian placement is the only problem? I have pointed out the existence of the morphological gaps earlier, and I am far from alone on this. Sure cladists can load up their PAUPs and get their results and be darn sure that they have a definitive answer. But when you have these huge morphological gaps obscured by the problems of pedomorphosis [a problem elaborated on by Schoch (1986), and AFAIK has not been adequately dealt with since]. IMHO cladists should be reminded that it is perfectly respectable to use the phrase incertae sedis.

Ruta M, Coates MI, Quicke DL. 2003. Early tetrapod relationships revisited. Biol Rev Camb Philos Soc. 78(2):251-345.

Schoch, RM. 1986. Phylogeny Reconstruction in Paleontology. Van Nostrand Reinhold.

While we are on the subject of non-dinosaurs, does anybody know of a good diagram of the superficial musculature of a modern crocidilian (any species will do)? I have searched ABSOLUTLEY EVERYWHERE and can't find a single one. (The exception, of course, being a diagram of very questionable accuracy in a kids' book: Zoobooks Crocodiles & Alligators. But even if it is accurate, the animal in the diagram is twisted in such a way that I can't see most of the neck and forelimb musculature.) I am in desperate need of help. If a kind soul out there somewhere could lend me a hand, it would be WILDLY apprectiated. Thank you.

Were'd everybody go? I certainly hope I'm not being pushy, but it's really important that some kind soul answer my question (comment 46). Maybe I should start begging. Here we go... PLEASE PLEASE PLEASE PLEASE PLEASE PLEASE PLEASE PLEASE PLEASE PLEASE PLEASE

> Lack of a terrestrial adult morph appears to be
> plesiomorphic for limbed vertebrates (Schoch 2001).

Yep. But in some cases, the terrestrial adult morph was lost secondarily.

> A mess? The only real problem is where the lissamphibians
> fit.

A rather big problem, especially if you consider the fact that the broad public still calls ALL stem tetrapods "amphibians".

> At least one of the authors of Palaeos.com loves his
> scenario-based phylogenies so much that he spent a lot of
> time and webspace on saying "Haaa! I found a hole in
> cladistics!!!1!" It gets annoying after a while.

Palaeos is full of rants and side-stories, dealing with everything from classical mythology to lovecraftian lore. Some of it is quite enlightening, some of it is entertaining, and some of it is plain weird. As a rule of the thumb, I consider this amusing rather than annoying. I know that they have a strong bias against molecular-based clades in general and afrotheres in peculiar; I haven't recognized an anti-cladistic bias yet, the sheer humungous size of Palaeos means that I haven't read all of it.

> What??? Do you mean Microbrachis, or do you maybe mean
> the branchiosaurid and micromelerpetontid temnospondyls?

*Microbrachis*.

> Pantylus is only known from terrestrial adults (unless
> Schoch's unsourced claim cited above is right -- as
> mentioned, I'll write to him).

This will be helpful :-)

> Yeah, right. It might have grown a fifth finger on the
> already fully ossified hand, a transverse flange on the
> pterygoid, a fucking supratemporal in the skull, a
> drastically more plesiomorphic skull-atlas joint, an axis
> intercentrumâ¦ Look, this is nonsense. I mean, I can't
> disprove it, but it fails epically at resisting Ockham's > Chainsaw.

Oops, I shouldn't have used *Pantylus* as a standard or model microsaur. This was a brainfart - when I hear microsaur, I think *Pantylus*, probably because it is the only member of this otherwise emo-like clade that has some charisma, sort of. *Microbrachis* would have been a better example of a pedomorphic microsaur.

I know that they have a strong bias against molecular-based clades in general and afrotheres in peculiar

Mr White had a change of heart regarding molecular trees some years ago; Palaeos being Palaeos, plenty of anti-molecular rants are still left scattered on the site, but newer pages are much more accepting of them.

(No idea what he thinks of Afrotheria specifically these days.)

Rainer Schoch has, admirably, already replied: He does not remember why he included Pantylus in that list, because he's not aware of any juveniles/larvae either; maybe it was just because he (like everyone else) thinks it was terrestrial (as an adult anyway). He told me to write to Andrew Milner; I'll tryâ¦

How "probably"?

It's the most parsimonious option.

The idea isn't new, either: the name "Holospondyli" for both goes back several decades.

Skulls are kinda quite different.

Forget Phlegethontia and Diplocaulus. Check out Sauropleura, Ptyonius and Lethiscus.

Same for caudals. From stem to stern.

"Nectrideans" and aÃ¯stopods share a fairly long list of pretty weird vertebral synapomorphies.

Mmm, yes, aÃ¯stopods, Diadectes, easily confused. :-)

Look at Hylonomus, Westlothiana and Tuditanus, and tell me that again. :-) Limnoscelis and Tseajaia differ from those mostly by sizeâ¦

I haven't seen Ruta & Coates (2007), does it differ much from Ruta et al. (2003)?

Not as much as it should (they added taxa, added characters, and removed a few correlated characters without properly fusing them; not a single mistake in the matrix was corrected!), but it does differ. You should get it one way or another, because it replaces the 2003 versionâ¦

Test to see if I can write a tree here or if that only works on Pharyngula:

--+--A
`--+--B
`--C

Anyway, Ruta & Coates (2007) find (Scincosaurus (Diplocaulidae (Urocordylidae, AÃ¯stopoda))), of which the first three are "nectrideans", next to Brachydectes (the lysorophian) and nested inside the "microsaurs".

The only real problem is where the lissamphibians fit.

Assuming monophyly for the group. Could be two or three problems.

Yes, but lissamphibian monophyly is by far the most parsimonious assumption from several independent lines of evidence (MarjanoviÄ & Laurin 2007, 2008a, 2008b, in press, and references therein).

Besides, lissamphibian placement is the only problem?

I wrote "the only real problem". It's the only major-league problem in here. There are of course minor-league ones -- "nectridean" monophyly or lack thereof, "microsaur" phylogeny, the position of Solenodonsaurus, the position of anthracosaurs and temnospondyls with respect to each other, the position and monophyly of the "gephyrostegids", the positions of Silvanerpeton and Caerorachis, the position of Casineria (but I repeat myselfâ¦ wait for the papers, or read chapter 8 of this thesis), the exact positions of "whatcheeriids" (probable but questionable monophyly), baphetids, colosteids, and Crassigyrinus with respect to each other, the already mentioned adelogyrinids and Acherontiscus, the exact positions of Acanthostega and Ichthyostega with respect to each otherâ¦ oh, and, temnospondyl phylogeny is a greater mess than one might think. :-) But the general shape of the tree has practically not changed at all since Carroll (1995).

Sure cladists can load up their PAUPs and get their results and be darn sure that they have a definitive answer.

LOL. Guess what I'm working on right now. Or just read our 2008b paper -- I'll post a link later; it's free-access.

Phylogenetics is hard workâ¦ :-)

But when you have these huge morphological gaps obscured by the problems of pedomorphosis (a problem elaborated on by Schoch (1986), and AFAIK has not been adequately dealt with since).

I cited Wiens et al. (2005) above; check it out. Its findings are applied in our 2008b paper and the in-press one.

IMHO cladists should be reminded that it is perfectly respectable to use the phrase incertae sedis.

Nope. Phylogenetics is a science now; you have to quantify your uncertainty. That's what all those bootstrap, jackknife and Bremer values and the Bayesian posterior probabilities are for, as well as all those winning-sites tests and whatnot.

Were'd everybody go? I certainly hope I'm not being pushy, but it's really important that some kind soul answer my question (comment 46).

Where in the world are you? Maybe everyone else was sleeping?

I for one have little idea about myology; I can't help you.

Palaeos is full of rants and side-stories, dealing with everything from classical mythology to lovecraftian lore. Some of it is quite enlightening, some of it is entertaining, and some of it is plain weird. As a rule of the thumb, I consider this amusing rather than annoying.

Oh, I agree: many of them are interesting and/or amusing. I especially enjoy the Jarvik saga: so true, so trueâ¦

this otherwise emo-like clade

:-D :-D :-D

Yes, Microbrachis was clearly paedomorphic (though much less so than any pre-/non-metamorphic branchiosaur).

Test to see if I can write a tree here or if that only works on Pharyngula:

Wow. What an epic fail.

@David: The link to that thesis doesn't work.

Hi,

Did any amphibian clade reversed from neoteny back to metamorphosis, or it is one way track?

"Yes. "Tadpole" is reserved for the stage before the extremely compressed metamorphosis of frogs."
wrote D. MarjanoviÄ

..and male children in the South eastern United States.

I've long been a bit...disappointed that mammals never
came up with the snake body plan, especially after being
razzed about 'Snow snakes' during my youth in North Dakota.
I wonder if isn't simply that the mammels simply haven't
gotten around to it yet...Weasels, minks, and the like
( Mustelids, I think? ) would seem to be good candidates
for an excercise in Spec. Zoology...

Will somebody PLEASE answer my question (comment 46)?

Sorry, I just saw that David had adressed my question, but couldn't help. Thanks anyway, David!

The link to that thesis doesn't work.

It does. Try again.

I wonder if isn't simply that the mammels simply haven't gotten around to it yet...Weasels, minks, and the like ( Mustelids, I think? ) would seem to be good candidates for an excercise in Spec. Zoology...

They already have a doubled resting metabolic rate to compensate for their disadvantageous surface-to-volume ratio. The maximum for endotherms can't be far away.

BTW, this is a computer, not a typewriter. You don't need to hit "Enter" at the end of a line. Line breaks are made automatically. :-)

Regarding mammalian snakes: The star nosed mole is probably the best candidate, it burrows through soft wetland soils and can smell underwater, eats superfast, amazing tentacles, etc.
http://en.wikipedia.org/wiki/Star-nosed_mole

Sort of related to topic..
Question: Sauropods have large pneumantic vertebrae, manatees have big super dense ribs, bony fish have many thin bones; so did early vertebrates (way before dinos) swim upside down with dense vertebrae as part-ossified ballast (like early turtle plastron), making them inverted invertebrates, then after developing an air sac, flip back right side up, then sauropods further lightened the vertebrae due to occasional (upright) shallow water wading and swimming? (I know 'semi-aquatic dinos' are old school, but I figure more primitive dinos were more water dependent, later ones much less so.)

IOW was the backbone & bony rib cage initially a ballast & armor trait? Is a notocord lighter than a vertebral column?

Do sharks have a (buoyant) myelin segmented sheath around the spine, while bony fish and tetrapods have a mineralised segmented sheath around the spine? (comment posted to tetzoo, pharyngula, SVPOW, AAT) Anyone know?

On the mammalian snake issue, has anyone mentioned the possibly legless fossorial hedgehog?

did early vertebrates (way before dinos) swim upside down with dense vertebrae as part-ossified ballast

Nope. Really early vertebrates did not have ossified vertebrae in the first place. They only had dermal bone.

making them inverted invertebrates

The evidence for the inversion hypothesis is a lot weaker than many people think. It looks obvious when you just compare chordates and arthropods, but add mollusks and flatworms, and it all breaks down.

then after developing an air sac, flip back right side up

Why wouldn't they develop it on the side that was up?

then sauropods further lightened the vertebrae due to occasional (upright) shallow water wading and swimming?

So you haven't been able to get Henderson's paper on how at least the most famous sauropods were basically too light to swim? They floated like corks and may have had their center of gravity above the waterline -- don't try this at home.

I figure more primitive dinos were more water dependent

Because of which evidence? Surely you've taken the dinosaur-filled Early Jurassic desert sediments of North America and southern Africa into account...?

was the backbone & bony rib cage initially a ballast & armor trait?

Would really surprise me. The armor was in the skin, and additional ballast wasn't needed.

Is a notocord lighter than a vertebral column?

I think so.

Do sharks have a (buoyant) myelin segmented sheath around the spine

What? Myelin is the isolation sheath around certain nerves. It doesn't occur anywhere else. And there's never enough of it to convey buoyancy -- the heaviest part of your body is the head, which is chock full of myelin.

On the mammalian snake issue, has anyone mentioned the possibly legless fossorial hedgehog?

The longer people look at it, the more probable it appears that it did have legs... we've been through that on the DML-KT...

David: Some people have hardly nothing but myelin in there.

Oh yeah, what was the name of that hedgehog? Googling "legless fossorial hedgehog" didn't get me an instant answer, so... David, still up? I vaguely recall having an online discussion and looking up the paper, but that was several years ago.

John, go here for starters. I asked Dougal Dixon about it; he's not sure where he got the idea of limblessness from, and it doesn't seem to be in the literature. Weird.

Thanks Darren! Should have searched the blog I was on, instead of the whole known universe. Of course!

It happens that several (but I'm not sure exactly how many) Proterix specimens are known, and NONE of them shows legs, and there's not a hint of a pectoral girdle or pelvic girdle to be seen. Either the hedgehog had crap luck preserving its limbs, or it had no limbs at all. I think Occam's Razor favors the latter.

That kind of preservation appears to be fairly common. Keep in mind that the mammalian pelvis-sacrum connection is just laughable (except in xenarthrans) -- in humans, it actually functions as a hinge joint during giving birth!!! --, and that it took people decades to figure out whether Diplocaulus had limbs.

"...it took people decades to figure out whether Diplocaulus had limbs."

Wow, I didn't know that. Thanks!

ARGH! Why didn't I read the text in the first picture more attentively? No known aÃ¯stopod has lost the postorbital bar. Instead, there's a temporal fenestra behind it. The triradiate bone in Phlegethontia is the squamosal, and the thing that looks like an antorbital fenestra is the orbit. The jugal is there (rostral to the squamosal), and dorsal to it is what appears to be a postfrontal-postorbital fusion product (judging from limited ontogenetic data) and contacts the frontal, which extends far caudally (just reaching the pineal foramen).

Well, I reckon I was looking at Anderson et al. (2003) when I wrote this: they state that the postorbital was lost between Ophiderpeton and Phlegethontia. I don't have Anderson's more recent papers to hand - Anderson (2002) is the one that smacks down the notion of cranial kineticism - but I guess I was fooled by the fact that (in Phlegethontia) the dorsal ramus of the jugal appears to lie adjacent to the lateral wall of the braincase.

Ref - -

Anderson, J. S. 2002. Revision of the aÃ¯stopod genus Phlegethontia (Tetrapoda: Lepospondyli). Journal of Paleontology 76, 1029-1046.

- ., Carroll, J. S. & Rowe, T. B. 2003. New information on Lethiscus stocki (Tetrapoda: Lepospondyli: Aistopoda) from high-resolution computed tomography and a phylogenetic analysis of Aistopoda. Journal of Paleontology 40, 1071-1093.

Oh - did you know that Bob Carroll has a new book coming out entitled The Rise of Amphibians: 365 Million Years of Evolution? It's due out this month, apparently.

they state that the postorbital was lost between Ophiderpeton and Phlegethontia.

Oh. Yes, they call the fusion product the postfrontal; Anderson (2002) goes on to show his ontogenetic mini-series, which has two tiny bones in place of the "postfrontal", one in the rostrodorsal corner, the other in the ventral one. Anyway, the bar is not lost.

did you know that Bob Carroll has a new book coming out

No, I had no idea.

Let's just hope he doesn't label the braincase of Phlegethontia "parietal" again. He's done that at least twice now.

Raise your hand if you love Palaeozoic non-amniote tetrapods. :)

I thought that, at least in American usage, "eft" referred to a terrestrial stage in the critter's life-style: the Red Eft, which after a while goes back to the water (and I think regrows a fin around its tail, and maybe changes color?) to breed. The relevant crittr being some species of newt. ("Eft" and "Newt" being, of course, etymologically connected.)

The relevant crittr being some species of newt.

Yes, the salamandrid Notophthalmus viridescens, which has a greenish aquatic adult morph. It's especially noteworthy for keeping its lateral-line organ throughout life: it's normal and functional in the aquatic larva, then sinks deep into the skin in the juvenile "red eft" stage, and then comes back out and works again in the adult (Schoch 2001).

Besides, it has been pointed out to me that I promised a link to my & Michel Laurin's 2008b paper in comment 50 but still haven't coughed it up. Here goes.

David, just a little question.
Do you know where to find info about family Ostodolepididae?
Or if you have something to say me about those microsaurs.
:)

Thanks.

DM Thank you.

Tetrapods of 2007 (happy birthday Tet Zoo part II)

tetrapodzoology — Sat, 26 Jan 2008 05:33:32 +0000

Tetrapods of 2007 (happy birthday Tet Zoo part II)

2007 - Tet Zoo's second year of operation - has come and gone. The previous article was a brief personal review of the year, and here's more of the same (sort of) if you can handle it...

As if Tet Zoo wasn't enough to deal with, in September my partners-in-crime Mike P. Taylor and Matt Wedel [shown here; Mike is the less big one] decided, with me, to start up a new zoological blog, but this time devoted to something a little more specific: namely, sauropod vertebrae (and nothing else, pretty much). So on October 1st, Sauropod Vertebra Picture of the Week, or SV-POW!, was born. Despite murmurings from some that we might struggle to find enough stuff to say for 52 posts, let alone any more than this, there is no doubt whatsoever that SV-POW! is going to be a long-term thing. Already it is world-famous, much-visited and aptly described by wikipedia as 'incredible' and 'highly popular among palaeontology afficianados'. It doesn't quite have the depth or breadth of Tet Zoo of course, but, hey, nearly 14000 visits within less than four months says it can't be wrong.

Technical research in 2007 and beyond

For whatever reason, I continued to produce and publish at least some academic research during 2007. In April, Dave Martill and I published part I of our review of British dinosaurs in the Journal of the Geological Society of London (part II is due to appear in May 2008) and, in May, the paper that Barbara Sánchez-Hernández, Mike Benton and I produced on the vertebrate fossils of Galve in Spain (Sánchez-Hernández et al. 2007) was published in Palaeogeography, Palaeoclimatology, Palaeoecology (we call it Palaeo3). In November, Mike P. Taylor and I published our long-awaited, earth-shattering new British sauropod, Xenoposeidon in Palaeontology, and the world went nuts. The appearance of Martill et al.'s book The Crato Fossil Beds of Brazil: Window into an Ancient World in December meant that my papers on Brazilian Cretaceous turtles (Naish 2007) and birds (Naish et al. 2007) were finally out.

Other academic work, yet to see the light of day, plodded along during the year. Mark Witton and I spent, literally, the better part of 2007 slowly putting together a big manuscript on the palaeobiology of azhdarchid pterosaurs, and even now it's too early to say when it'll see publication (though it has been submitted). And together with Mike P. Taylor, Paul Upchurch, Adam Yates, and Matt Wedel, I thrashed out a couple of articles on... well, wait and see! Dave Hone and I also worked together on cranial crest distribution in archosaurs. I've been unable to deal with what is, arguably, my priority: the publication of the several papers that should come out of my 2006 phd thesis. Eventually, the papers on Yaverlandia, Eotyrannus, Becklespinax and Valdoraptor will see publication, but I don't know when. At least one Wealden theropod paper did get well underway however (co-authored with Steve Hutt, Steve Brusatte and Roger Benson). A paper on Neovenator and an associated iguanodontian, co-authored by Dave Martill and the late David Cooper, was delayed, again [adjacent image shows me selt-consciously working on Valdoraptor, and surrounded by Wealden sauropod vertebrae. Photo courtesy Mike P. Taylor].

Despite the fact that I've been consistently un-funded, and have a family and have had to do a lot of crappy jobs, I remain somewhat smug about the fact that I manage to publish more technical research papers than many salaried academics I can think of. Yeah, they can often argue that they have teaching to deal with, but I don't see them staying up until 3 or 4 in the morning to get their papers written. In fact, just what the bloody hell do other academics do with their time? And, no, I do not have those of you in mind who publish three or more papers a year. Although my time at the University of Portsmouth effectively finished with the completion of the phd, I'm pleased to say that I was awarded the position of honorary research associate late in 2007, so, for the time being at least, I can continue to justify leaving my posters on the wall, and my taking up of valuable desk space.

The tetrapods of 2007

2007 was a particularly interesting year for several groups of animals I've written about on Tet Zoo, but then I think you might say that about most years. On Palaeozoic tetrapods, we had a pretty good sampling of new papers on temnospondyls (particularly on mastodonsauroids), including on their scalation, colour patterns (Werneburg 2007) and on direct evidence for their role in Permian food webs (Kriwet et al. 2007) [adjacent image shows food chain figure from Kriwet et al. (2007). Temnospondyl eats acanthodian. Xenacanthid shark eats temnospondyl]. Non-mammalian synapsids (including dicynodonts, burnetiamorphs, traversodontids and tritylodontids) were in the journals a bit, and we saw the new Mesozoic mammals Nanocuris, Ferganodon, Gondtherium, Yanoconodon, Dakshina, Bharattherium, Argentodites, Argentoconodon, Pseudotribos and Maelestes! If you google Dakshina you'll see why it was a poorly chosen name - anyway, it may well be synonymous with Bharattherium.

A major work on Mesozoic turtles saw publication (Joyce 2007) and the incredible long-necked gliding Mecistotrachelos was described (Mecistotrachelos is a possible protorosaur and relative of Tanystropheus: it's shown at the top of the image below). Having mentioned Tanystropheus, Nosotti's new monograph on this taxon appeared, finally updating Wild's classic (but much outdated) work of 1973. And on weird gliding reptiles, a new specimen of Coelurosauravus was described, and the Cretaceous gliding lizard Xianlong was announced. New basal snakes, long-bodied anguimorphs and mosasauroids joined the ranks, as did the beautifully preserved Cretaceous iguanian Saichangurvel, the most basal member of the newly recognized gobiguanian clade. Choristoderes were in the news what with the discovery of a two-headed baby.

Research on Triassic archosaurs, including crurotarsans and early dinosaurs and their relatives, had a good year, and several new Mesozoic theropods, including a giant dromaeosaur-eating compsognathid (Sinocalliopteryx: shown in middle of adjacent image), new therizinosauroids, an alvarezsaurid, and the immense oviraptorosaur Gigantoraptor, were published. The tenth Archaeopteryx specimen - the best one yet - was monographed (Mayr et al. 2007), and feather quill knobs were reported in Velociraptor (Turner et al. 2007). It was also a significant year for the sauropodomorph dinosaurs we used to call prosauropods, with an important volume devoted entirely to these neglected dinosaurs seeing publication. A surprising amount was published on ceratopsians, including announcements of new species as well as new data on their biology, phylogeny and distribution. At last, a good response to all that nonsense about skim-feeding in pterosaurs was published (Humphries et al. 2007).

As goes fossil Cenozoic tetrapods, the research renaissance on fossil penguins, beaked and baleen whales, and sloths continued, a lot of neat new stuff was published on phorushacids (I'll be covering this later), and several papers appeared on both new and old island-dwelling crocodilians. Key new papers appeared on raoellids (a group of Eocene artiodactyls now thought to be the sister-taxon to whales), early plesiadapiforms (basal members of Primates), the fossorial mesotheriid notoungulates, and bizarre little Necrolestes from the Miocene of Patagonia. New fossil hominids, including those from Georgia, Lake Turkana in Kenya and Flores, continued to be big news, as was the discovery of Neanderthals in central Asia and Siberia, and the late Miocene Chororapithecus [shown at bottom of adjacent image], allegedly the oldest known member of the gorilla lineage (Suwa et al. 2007).

On living animals, we had the amazing announcement that wolves Canis lupus might be three phylogenetically distinct species (Aggarwal et al. 2007), and the publication of Leonard et al.'s paper on a hitherto undocumented robust-skulled Pleistocene wolf morph from Beringia (Leonard et al. 2007). The announcement of a resurrected clouded leopard species caused a stir. Continuing argument over the validity of the Kouprey Bos sauveli resulted in at least four new papers on this subject, and the dwarf Antarctic killer whale was recognised as distinct in a study by Pitman et al. (2007). Morphological synapomorphies were finally identified for Afrotheria (Sánchez-Villagra et al. 2007). Long-awaited papers on the phylogeography and taxonomy of giraffes appeared, and equally long-awaited was Livezey & Zusi's (2007) massive analysis of neornithine bird phylogeny. This is the ultimate morphology-based look at bird phylogeny, but it certainly hasn't ended the debate and already other ornithologists are complaining about it (e.g., Mayr 2007).

More was published about the bird-eating habits of noctule bats, chimps were shown to hunt using spears, and it was proposed both that the origin of bipedality may have originated near the base of Hominoidea (Filler 2007), and that hominoid bipedality originated in arboreal taxa that first used bipedality as a means of locomoting on flexible branches (Thorpe et al. 2007a, b). The Giant peccary Pecari maximus, Mindoro stripe-faced fruitbat Styloctenium mindorensis [shown in adjacent image], Otto's sportive lemur Lepilemur otto, Manasamody sportive lemur L. manasamody, Uganda mangabey Lophocebus ugandae, White-lipped keelback Amphiesma leucomystax (a Vietnamese natricine snake), Ashe's spitting cobra Naja ashei, Central Ranges taipan Oxyuranus temporalis, Gorgeted puffleg Eriocnemis isabellae (a hummingbird from Colombia), Rufous twistwing Cnipodectes superrufus (a tyrant flycatcher) and Solomon Islands frogmouth Rigidipenna inexpectata were all formally described during the year. A surprising amount was published on burrowing snakes. Speciation by allochrony - a real big deal, but apparently missed by science journalists - was documented in the Madeiran or Band-rumped storm petrel Oceanodroma catro (Friesen et al. 2007).

Toward the end of the year I became increasingly involved in writing about living amphibians, firstly because I wanted to help out with the EDGE amphibians project (which of course launched earlier this week), and secondly because I was asked to help promote the Year of the Frog launch. I've always been passionate about conservation but have rarely had the chance to do much about it. At least now I can say I've done something: if you're interested in amphibians, and concerned about the global declines that many species are experiencing, please sign the Amphibian Ark petition - go here, it only takes about 20 seconds to complete the process.

So, here we are, in 2008. My own future is uncertain and frightening, but I don't think it can get worse. We have a lot to forward to in 2008 and beyond.

Refs - -

Aggarwal, R. K., Kivisild, T., Ramadevi, J. & Singh, L. 2007. Mitochondrial DNA coding region sequences support the phylogenetic distinction of two Indian wolf species. Journal of Zoological Systematics and Evolutionary Research 45, 163-172.

Filler, A. G. 2007. Homeotic evolution in the Mammalia: diversification of therian axial seriation and the morphogenetic basis of humans origins. PLoS ONE 2, No. 10, e1019 doi:10.1371/journal.pone.0001019

Friesen, V. L., Smith, A. L., Gómez-Diaz, E., Bolton, M., Furness, R. W., González-Solis, J. & Monteiro, L. R. 2007. Sympatric speciation by allochrony in a seabird. Proceedings of the National Academy of Sciences 104, 18589-18594.

Humphries, S., Bonser, R. H. C., Witton, M. P. & Martill, D. M. 2007. Did pterosaurs feed by skimming? Physical modelling and anatomical evaluation of an unusual feeding method. PLoS Biology 5, No. 8, e204 doi:10.1371/journal.pbio.0050204

Joyce, W. G. 2007. Phylogenetic relationships of Mesozoic turtles. Bulletin of the Peabody Museum of Natural History 48, 3-102.

Kriwet, J., Witzmann, F., Klug, S. & Heidtke, U. H. J. 2007. First direct evidence of a vertebrate three-level trophic chain in the fossil record. Proceedings of the Royal Society B 275, 181-186.

Leonard, J. A., Vilà, C., Fox-Dobbs, K., Koch, P. L., Wayne, R. K. & Van Valkenburgh, B. 2007. Megafaunal extinctions and the disappearance of a specialized wolf ecomorph. Current Biology 17, 1146-1150.

Livezey, B. C. & Zusi, R. L. 2007. Higher-order phylogeny of modern birds (Theropoda, Aves: Neornithes) based on comparative anatomy. II. Analysis and discussion. Zoological Journal of the Linnean Society 149, 1-95.

Mayr, G. 2007. Avian higher- level phylogeny: well-supported clades and what we can learn from a phylogenetic analysis of 2954 morphological characters. Journal of Zoological Systematics and Evolutionary Research doi: 10.1111/j.1439-0469.2007.00433.x

- ., Pohl, B., Hartman, S. & Peters, D. S. 2007. The tenth skeletal specimen of Archaeopteryx. Zoological Journal of the Linnean Society 149, 97-116.

Naish, D. 2007. Turtles of the Crato Formation. In Martill, D. M., Bechly, G. & Loveridge, R. F. (eds) The Crato Fossil Beds of Brazil: Window into an Ancient World. Cambridge University Press (Cambridge), pp. 452-457.

- ., Martill, D. M. & Merrick, I. 2007. Birds of the Crato Formation. In Martill, D. M., Bechly, G. & Loveridge, R. F. (eds) The Crato Fossil Beds of Brazil: Window into an Ancient World. Cambridge University Press (Cambridge), pp. 525-533.

Pitman, R. L., Perryman, W. L., LeRoi, D. & Eilers, E. 2007. A dwarf form of killer whale in Antarctica. Journal of Mammalogy 88, 43-48.

Sánchez-Hernández, B., Benton, M. J. & Naish, D. 2007. Dinosaurs and other fossil vertebrates from the Late Jurassic and Early Cretaceous of the Galve area, NE Spain. Palaeogeography, Palaeoclimatology, Palaeoecology 249, 180-215.

Sánchez-Villagra, M. R., Narit, Y. & Kuratani, S. 2007. Thoracolumbar vertebral number: the first skeletal synapomorphy for afrotherian mammals. Systematics and Biodiversity 5, 1-7.

Suwa, G. Kono, R. T., Katoh, S., Asfaw, B. & Beyene, Y. 2007. A new species of great ape from the late Miocene epoch in Ethiopia. Nature 448, 921-924.

Thorpe, S. K. S., Crompton, R. H. & Alexander, R. McN. 2007a. Orangutans utilise compliant branches to lower the energetic cost of locomotion. Biology Letters doi:10.1098/rsbl.2007.0049

- ., Holder, R. L. & Crompton, R. H. 2007b. Origin of human bipedalism as an adaptation for locomotion on flexible branches. Science 316, 1328-1331.

Turner, A. H., Makovicky, P. J. & Norell, M. A. 2007. Feather quill knobs in the dinosaur Velociraptor. Science 317, 1721.

Werneburg, R. 2007. Timeless design: colored pattern of skin in early Permian branchiosaurids (Temnospondyli: Dissorophoidea). Journal of Vertebrate Paleontology 27, 1047-1050.

tetrapodzoology Sat, 01/26/2008 - 00:33

Tags

Categories

Nice post...Let's hope 2008 will be as good!!
For the history it's Saichangurvel (not Sachiangurvel)

Darren,

Thank you very much for your efforts. I have really enjoyed your blog, which I consider one of the best, if not THE best, on the web. I have not always agreed with your conclusions, but I have found your articles fascinating and well argued.

I hope your skills and abilities are recognised by those in a position to reward them, such as by a decent job that pays well (though obviously one that leaves you enough time to keep Tetzoo going).

Once again, thank you and best wishes, have a wonderful 2008.

Thanks Georgios and Mark for your kind words and support. Mark: out of interest, which conclusions of mine haven't you agreed with? All the best.

Good luck from all local tetrapods!

BTW - considered moving elsewhere? This must be *** of university not to give you position.

Mesozoic turtles and "the incredible long-necked gliding Mecistotrachelos" in close proximity spark pleasant mental images of flying turtles..... Hmmm. Next April 1?

Darren,

your publication record is genuinely impressive given your commitments. All I would say is that teaching is indeed a time sapper, but so is the grant writing. To write a proper serious grant takes me (at the moment, I am sure it will accelerate with time) about 3 weeks full time, and I write 3 or 4 a year. Plus teaching and supervising student projects etc. It soon mounts up.

Still, well done and keep the publications coming. You'll be dlighted to know the crest stuff is well on track! I'll try and give you a month or two before the next session!

Best wishes for work, life and research!

About those skimming pterosaurs... I have been thinking about the extreme headgear on some. One substantial effect I have not seen discussed is that it would give the head a very large moment of rotational inertia per unit of excess lofted mass. That could make it actually useful, allowing the creature (e.g.) to dip its beak/snout in the water while flying (and maybe catch something) without having its whole head snapped instantly downward, as happens to birds that dip on the wing. It might be equally effective for snatching lizards sunning themselves on high rocks without risk of (pterosaur) neck trauma, so this isn't actually an argument for skimming.

If you google Dakshina you'll see why it was a poorly chosen name

That might have been deliberate.

a new specimen of Coelurosauravus was described

What? Where?

And what is the new alvarezsaurid???

Morphological synapomorphies were finally identified for Afrotheria

Autapomorphies. One taxon has autapomorphies (auto- "self), two taxa share synapomorphies (syn- "together"). Hey, it's not my fault Hennig loved making up technical terms just for the fun of it. :-}

This is the ultimate morphology-based look at bird phylogeny, but it certainly hasn't ended the debate and already other ornithologists are complaining about it (e.g., Mayr 2007).

Well yes. There are almost no fossils in the matrix. No wonder it gets such surprising results. Livezey & Zusi were not megalomaniac enough :o)

Plus, a few hundred of the characters are parsimony-uninformative. Adding yet more taxa ought to help here, too.

It's been a great year for tetrapods! Speaking of which, does anybody have a copy of the Sinocallipteryx paper? That's one compsognathid I can't get my hands on.

Thanks for comments everyone, and for best wishes etc. Quick responses to a few things... mostly to David, as usual :) ...

New Coelurosauravus specimen..

Schaumberg, G., Unwin, D. M. & Brandt, S. 2007. New information on the anatomy of the Late Permian gliding reptile Coelurosauravus. Paläontologische Zeitschrift 81, 160-173.

New alvarezsaurid is Achillesaurus mannazonei..

Martinelli, A. G. & Vera, E.I. 2007. Achillesaurus manazzonei, a new alvarezsaurid theropod (Dinosauria) from the Late Cretaceous Bajo de la Carpa Formation, Río Negro Province, Argentina. Zootaxa 1582, 1-17.

Use of term 'synapomorphies' for one taxon: you're right, but what I (and Sánchez-Villagra et al.) are saying is 'we found a synapomorphy that unites afrotherians'.

And.. Sinocalliopteryx. There is a pdf out there, stay tuned and I'll send it (unless anyone beats me to it).

Thanks, sir! And just because you know I'd ask: How 'bout Achillesaurus too? :-)

This is a wonderful blog! I am very glad that I stumbled upon it in 2007 -- I learn so much here that I would not have heard of otherwise, about tetrapods living and extinct.

Happy birthday, and please do continue! Here's to a great 2008!

Happy Blog-birthday!

Your posts are always unique, well researched, and well-written, and I enjoy them very much.

Don't know whether you've seen Dr. R. Lang's origami pteranodon in the Redpath Museum, but here's a link just in case you haven't (a small birthday present, I guess):

http://www.langorigami.com/art/monumental/monumental.php4

You, sir, are a zoologist without peer. Congratulations on your second year bringing the tetrapods to the masses. Your work here, your intimidating publishing record, your sitcom-worthy adventures in making a living--any one of the three would be an achievement. That you managed them all at the same time is nuts. If you get into an academic job we're all doomed. But I wish you the best of luck. Someone's bound to notice and offer you an endowed chair one of these days.

Thanks for finding a picture that doesn't make me look like Fatsquatch.

Survivors, diggers, herbivores, first giant terrestrial vertebrates: the caseids

tetrapodzoology — Mon, 16 Jul 2007 04:48:05 +0000

Survivors, diggers, herbivores, first giant terrestrial vertebrates: the caseids

Among the many, many groups I have yet to cover on Tet Zoo are stem-group synapsids: Synapsida is the tetrapod clade that includes mammals and all of their relatives, and there is a long tradition of referring to non-mammalian synapsids as 'mammal-like reptiles' (other names include protomammals and paramammals). Because synapsids are not part of Reptilia*, referring to them as 'mammal-like reptiles' is both technically incorrect and misleading, hence the push to use their proper name.

* Reptilia and Synapsida are sister-taxa within the tetrapod clade Amniota.

The photo here was provided by Matt Wedel and shows the mounted skeleton of the Early Permian non-mammalian synapsid Cotylorhynchus hancocki, as mounted at the Oklahoma Museum of Natural History. Because I haven't had time to finish any proper articles lately, this provides me with a good excuse to talk briefly about Cotylorhynchus and its relatives. Or, not so briefly, as it turns out...

Cotylorhynchus is the best known representative of the basal synapsid clade Caseidae, a group that is odd for lots of reasons. While caseids are among the most basal of all synapsids, they don't make their first appearance until relatively late in basal synapsid history: they debut in the Early Permian, whereas four of the six other basal synapsid clades (varanopids, ophiacodontids, edaphosaurids and sphenacodontids) were all present in the Carboniferous*. Caseids must therefore have a long ghost lineage that extends back to the Carboniferous (Reisz et al. 1998), and the very earliest, most primitive members of the group remain unknown.

* All of these basal synapsids were formerly grouped together as Pelycosauria: because this group is paraphyletic, 'pelycosaur' is only used informally today. Eupelycosauria is a formal clade name however - it's the sister-group within Synapsida of Caseasauria [read on].

Caseids almost certainly descended from small carnivorous forms, but experts have disagreed as to whether their closest relatives were the eothyridids or varanopids. Reisz (1980) noted that caseids shared with eothyridids the same sort of tilted anterior margin of the premaxilla (where the dorsal surface of the snout tip extends further rostrally than the mouth), an elongated external nostril, and a shortened face where the maxilla contributed to the margin of the orbit (in other basal synapsids, the lacrimal and jugal keep the orbit and maxilla well apart). Consequently he grouped the two together in a clade, for which the name Caseasauria Williston, 1911 already exists. I think that eothyridids look like good 'proto-caseids'; unlike caseids, they possessed enlarged caniniform teeth and were presumably predatory [adjacent image is life restoration of Cotylorhynchus].

Indeed, caseids are unusual among basal synapsids in that all known members of the group were herbivorous, as is demonstrated by their proportionally small skulls, spatulate teeth, absence of any sort of caniniform region in the dentition, and by their massive broad bodies* (Sues & Reisz 1998). So far as we can tell, these features were true of Oromycter dolesorum, the oldest and apparently most basal caseid (Reisz 2005). Probably c. 1 m long, it was much smaller than some of the later members of the group: Cotylorhynchus romeri (the presumed ancestor of the slightly larger, geologically younger C. hancocki) from the late Early Permian reached 3.5 m in length and had an estimated weight of 330 kg (Stovall et al. 1966). It was gigantic compared to many of its relatives and contemporaries, and in fact it and C. hancocki were the largest 'pelycosaurs' and largest terrestrial vertebrates of their time.

* Some caseids, such as Caseopsis agilis, were slimmer-bodied than the best known forms, but were still otherwise similar.

As you can see from the accompanying picture, Cotylorhynchus had a massive scapulocoracoid, enormous flaring ends on its humeri, stout forearm bones, and broad, robust hands with large claws. Large retractor processes on the ventral surfaces of the unguals show that caseids could flex their claws with a very powerful motion, and the articulatory surfaces of phalanges weren't perpendicular to the bone's long axis, but oblique to it, thereby providing a much larger surface area for flexor muscles. These features all suggest that 'in life the animal did considerable digging for its food supply' (Stovall et al. 1966, p. 23). I wonder if they constructed burrows. Articulated specimens confirm that the digits had a considerable range of motion: in a specimen kept at the Cleveland Museum of Natural History, the toes are folded right under the rest of the foot, with the claws pointing backwards towards the tail. One odd thing I'd like to know more about concerns the apparent variation that exists in the size of the hand claws of Cotylorhynchus: some specimens seem to have rather longer unguals than others (look at figs. 13 and 14 in Stovall et al. (1966)). Is this genuine variation? If so, it is sexual or ontogenetic or what?

Why is the early history of caseids so poorly known? Olson (1968) proposed that these animals spent the early part of their evolutionary history in areas that were well away from the lowland/deltaic environments that were best incorporated into the fossil record. This hypothesis is supported by the discovery of the new basal caseid Oromycter in an upland depositional setting, and specimens from upland environments at the rich Bromacker site in Germany provide further support for this (Reisz 2005). The inference is that it took caseids a considerable time to change from living in remote upland habitats to the better-sampled, lowland flood-plain environments where most of our Carboniferous and Permian fossils come from.

Despite the fact that they were so archaic within the synapsid family tree, caseids became the most abundant Early and Middle Permian herbivores in North America at least, out-living their herbivorous cousins the sail-backed edaphosaurids. Ennatosaurus from Russia shows that caseids survived to near the end of the Middle Permian to live alongside dinocephalians and other therapsid synapsids [image of Ennatosaurus above borrowed from here].

As always there's much more to say, but that'll have to do. This was only meant to be a picture of the day submission, but I suppose I got carried away. I must do more stem-group synapsids in the future.

Refs - -

Olson, E. C. 1968. The family Caseidae. Fieldiana: Geology 17, 223-349.

Reisz, R. R. 1980. The Pelycosauria: a review of phylogenetic relationships. In Panchen, A. L. (ed) The Terrestrial Environment and the Origin of Land Vertebrates. Academic Press (London/NY), pp. 553-592.

- . 2005. Oromycter, a new caseid from the Lower Permian of Oklahoma. Journal of Vertebrate Paleontology 25, 905-910.

- ., Dilkes, D. W. & Berman, D. S. 1998. Anatomy and relationships of Elliotsmithia longiceps Broom, a small synapsid (Eupelycosauria: Varanopseidae) from the Late Permian of South Africa. Journal of Vertebrate Paleontology 18, 602-611.

Stovall, J. W., Price, L. I. & Romer, A. S. 1966. The postcranial skeleton of the giant Permian pelycosaur Cotylorhynchus romeri. Bulletin of the Museum of Comparative Zoology 135, 1-30.

Sues, H.-D. & Reisz, R. R. 1998. Origins and early evolution of herbivory in tetrapods. Trends in Ecology & Evolution 13, 141-145.

tetrapodzoology Mon, 07/16/2007 - 00:48

Tags

Palaeozoic tetrapods

picture of the day

stem-synapsids

what a wonderful group of animals and so often completly ignored.
personally I've been arguing they are more 'reptile-like mammals' than 'mammal-like reptiles' for years!

Nice post on caseids. Fascinating animals; they are so ugly that they become beautiful again, like french airplanes of the interwar years (look here: jnpassieux.chez-alice.fr/html/FarmanF120.php for an example that had a diminutive radial engine attached at the same position were caseids had their equally tiny heads:-)). What is frustrating about stem synapsids, however, is the fact that the anatomically most primitive ones, like eothyridids, appear so late in the fossil record.

BTW, if we are already in the Permian: Give us gorgonopsians, please!

Absolutely wonderful post, Darren; thank you for writing this one up. Like you mentioned, despite the terms inaccuracy "mammal-like reptile" still seems to be in wide use, and a clarification in more popular works needs to be made. Like Phil said, thanks for giving another often-ignored group some much-needed attention.

Wow, a fascinating group. Their robustness and sprawling suspension is somehow tortoise-like, no? It's hard not to believe they were burrowers. They had to be slow-pokes, and digging burrows with those spades in front would offer protection against predators, and perhaps provide a means of regulating body temperature. Neat creatures.

Johannes, if you´re interested in Gorgonopsians you could like this photo of a Dinogorgon quinquemolaris-skull I made some time ago: http://bestiarium.kryptozoologie.net/?p=79

other names include protomammals and paramammals

But the best term (for both succinctness and precision) is "stem-mammal".

"Protomammal" makes it sound like they are the ancestors of mammals, when most were not. It also sounds like they appeared before mammals, when many were contemporaneous. As noted elsewhere on this blog, I think, some were still around even into the Cretaceous.

"Paramammal" is a bit better, but to me it makes it sound like their similarity to mammals may only be due to coincidence. At the very least, it emphasizes the similarity without any hint that that similarity is due to common ancestry.

"Stem-mammal", on the other hand, says exactly what the group is: all members of the total group (Pan-Mammalia/Synapsida/Theropsida) which are not members of the crown group (Mammalia).

Woohoo! Finally, some hot synapsid action!

Okay, a bit of an evolutionary origination query: in reading, it seems a bit of question whether or not the amniotes are paraphylitic? The reason I am asking is that while reading up a bit, I get the impression that one of three scenarios took place: there were three separate originations out of the amphibians (synapsids, diapsids, anapsids); there were two (synapsids and diapsids with the anapsids deriving out of the diapsids); or there was a single event from the amphibians and the th events of the *apsids were all subsequent.

I would think that it was the last, but some of the impressions I've been getting make it seem that the amniotes are not monophylitic at all. umm. Can I get a clarification from those that are pros int he area?

Again, thanx for more on our synapsid paleo-cousins, Darren!

Great post! How did those things even operate with such tiny heads?! Isn't some variation on "Pelycosauria" still around to include Dimetrodon, Edaphosaurus, and their cousins?

While some large sauropods and tortoises probably have similarly tiny heads, I've long wondered how Cotylorhynchus managed to get by without a long neck. Something as simple as getting a drink of water must have been a hilariously awkward undertaking, if it ever did drink that is. I yearn for the day to see a CGI caseid bumbling around, well, and many other things.

Sigh, too bad people out there don't pay attention to all the fascinating beasties out there besides dinosaurs.

But the best term (for both succinctness and precision) is "stem-mammal".

"Protomammal" makes it sound like they are the ancestors of mammals, when most were not. It also sounds like they appeared before mammals, when many were contemporaneous. As noted elsewhere on this blog, I think, some were still around even into the Cretaceous.

"Paramammal" is a bit better, but to me it makes it sound like their similarity to mammals may only be due to coincidence. At the very least, it emphasizes the similarity without any hint that that similarity is due to common ancestry.

"Stem-mammal", on the other hand, says exactly what the group is: all members of the total group (Pan-Mammalia/Synapsida/Theropsida) which are not members of the crown group (Mammalia).

Yeah, ok. But - to clarify - I was specifically referring to vernacular names that have historical precedent in the literature. Out of interest, has anyone ever referred to stem-group synapsids as 'stem-mammals'? There have been a few efforts to get the name Mammalia extended all the way down to the synapsid root (Ax 1987 for example, I think), but they clearly haven't been successful.

Phil More,

Agree regarding reptile-like mammals. As a matter of fact, there might be a case for amphibian-like mammals.

For my part I reserve "proto-mammals" for the ancestors of marsupials --- which would include the triconodonts/monotremes. Quasi-mammals would include groups such as the multituberculates and docodonts.

A synapsid post! The mammalian chauvinist thanks you!

(i) Neat that the life reconstruction of Cotylorhyncus is from the same angle as the photo of the mounted skeleton. Lucky accident, or did Matt Wedel have this in mind when he took the photo?

(ii) The most striking thing about the skull of Casea is its IMMENSE nostrils. Any speculation about function? (Totally groundless speculation: Basal amniotes had no very efficient air-pumping mechanism -- synapsids of the Therapsid line seem to have evolved the mammalian system with a muscular diaphragm, suggesting that more basal forms weren't good at deep breathing -- and the caseids, as recent elvovers of large body size, needed air any way they could get it: enlarging the diameter of the airways evolved in response. As I said, TOTALLY groundless speculation!)

(iii) (To Will Baird) Available evidence is that amniotes arose from one branch of the paleozoic tetrapod tree (somewhere not TOO far from Seymouriamorphs). So whther they are mono- or poly- becomes something of a matter of definition: do we draw the line between amniote and pre-amniote just above or just below the last common ancestor. Similar questions arise with mammals: do multituberculates have a MAMMALIAN common ancestor with us or not? Even if not, though, they are now seen as having a more recent (and more mammal-like) common ancestor with us than some early 20th C. speculations suggested.

Great post, and good point about the incorrectness of "mammal-like reptiles", I had actually never thought about that before but you're very right, as usual. ;)

Is the museum you mentioned the one in Norman, Oklahoma? I got to spend the night there over Christmas break, they have some fantastic exhibits. We got to tour some of the collections, they've got some magnificent Australasian bird specimens, and I even got my picture taken with their voucher Jackalope. ;)

> there were three separate originations out of the amphibians (synapsids, diapsids,
> anapsids); there were two (synapsids and diapsids with the
> anapsids deriving out of the diapsids); or there was a single event from the amphibians
> and the th events of the *apsids were all subsequent.

Most sources tend to support your third alternative, in other words: monophyly of amniotes. Try palaeos or Tree of life for a start.

BTW: Be careful when using the term "amphibians" for stem tetrapods. It is by no means clear which stem tetrapod clade is the ancestor of lissamphibians (Temnospondyls? Lepospondyls?), but either alternative would leave many other stem tetrapod clades that are not closer related to lissamphibians than to mammals, birds or turtles.

Fat-bodied, lived in upland environments, small, obligate herbivores, possibly good digging skills?

Sounds like a marmot analogue.

Neat that the life reconstruction of Cotylorhyncus is from the same angle as the photo of the mounted skeleton. Lucky accident, or did Matt Wedel have this in mind when he took the photo?

Lucky accident! I had never seen that life restoration when I took the photo. I was just trying to find an angle that showed how deeply, deeply weird this animal is. Unfortunately the photo does not convey the scale very well--that skeleton is probably 9 or 10 feet from nose to tail.

I just posted some more photos of the specimens on display at the OMNH. Click the "posted by" link below.

It is very strange to stand in front of that fat, squat, pin-headed neckless freak, which looks like nothing so much as a microcephalic chuckwalla, and think that when it was alive, it was the largest terrestrial vertebrate of all time--the Amphicoelias of the Early Permian.

Great post, Darren. There are so many interesting but obscure clades from the Late Paleozoic that you could probably spend a year doing nothing but. I know that your mandate is broader, and I appreciate it, but this post shows that there is a market for these weirdos. Keep 'em coming.

I never noticed some Caseids had such small heads.

Great post on an underrated group of Synapsids.

Thanks for writing what you did. My education in biology ended with the obligatory class in college, but the wonder of life's variety, past and present, great and small, still enthralls me.

And I have been voted "coolest mom ever" by a five year old for being able to look at a cast of a dinosaur skeleton and at a glance name the species (thanks to Peter Dodson's book, I knew it was C. belli.)

I thought that skeleton was missing its head, until I saw the life restoration and took another look at the photo. That is indeed one deeply, deeply weird animal.

But then all those early synapsids are deeply weird to me. If I were completely unfamiliar with them and dinosaurs and had to pick one group to have been the work of evolution and another the work of an artist's imagination, I'd pick those early synapsids as the work of an artist. They seem much more alien than the dinosaurs which seem to make more 'sense' as functioning animals.

most interesting. now I finally know something about those tiny-headed skeletons. thank you.

>Caseids must therefore have a long ghost lineage that extends back to the Carboniferous
If I may suggest something...maybe the Caseids arose from another synapsid clade during the Permian and (not sure what the technical term is) evolved in a more basal direction while/followed-by specializing as diggers.

tis just a thought.

Did *any* Caseids survive to the Triassic?

Did *any* Caseids survive to the Triassic?

Not so far as we know, no.

Many thanks to everyone for their comments - sorry that I don't have time to respond to everything.

- Varanopseidae is incorrect; Varanopidae is correct.
- Please, please, drop the name Reptilia. It only sows confusion and comes with centuries of baggage. Just say Sauropsida; it's the same anyway.
- Eupelycosauria was a bad idea -- so bad that the PhyloCode now recommends against it.
- Caseids are mind-boggling, but the edaphosaurids had a way cooler dentition: incisor analogues outside (premaxilla, maxilla, dentary), molar analogues inside (pterygoid, coronoid III, prearticular -- yes, prearticular, like in lungfish -- yes, prearticular, a bone that we have in the middle ear).
- No, Ennatosaurus is not Late Permian. It is Middle Permian. There is no Late Permian in Russia (according to A Geologic Time Scale 2004), unfortunately.

----------------

- A long row of reversals leading to caseids? There's no evidence for that. It would be a mightily unparsimonious hypothesis. They, plus Eothyrididae, really must have a ghost lineage that leads way back into the Carboniferous.
- Are caseid nostrils really enormous relative to body size? Or only to skull size, which would be expected given the absurdly tiny skull?
- No, there is no version of Pelycosauria around anymore. Dimetrodon is more closely related to you than to Edaphosaurus.

Fat-bodied, lived in upland environments, small, obligate herbivores, possibly good digging skills?

Sounds like a marmot analogue.

Ten times the length of a marmot, not small!

[from Darren: thanks David, I will correct the article in view of some of these comments. But I'm not dropping Reptilia until everyone else does]

> Caseids are mind-boggling, but the edaphosaurids had a way cooler
> dentition

When discussing the early permian terrestrial herbivorous "giants", we should not forget Diadectes. This animal is really weird and fascinating: A terrestrial herbivorous tetrapod that is not even an amniote.

There have been a few efforts to get the name Mammalia extended all the way down to the synapsid root (Ax 1987 for example, I think), but they clearly haven't been successful.

To be clear, I'm not advocating this. "Stem-X" means "everything closer to X, a crown group, than to any other crown group, but not part of X". Or, put another way, "pan-X (total group) minus X".

I wrote:

There is no Late Permian in Russia (according to A Geologic Time Scale 2004), unfortunately.

But Benton and friends doubt thisâ¦

This animal is really weird and fascinating: A terrestrial herbivorous tetrapod that is not even an amniote.

Well, no, but almost. It may well have laid amniotic eggs (â¦if the alleged traces of lateral-line canals in various diadectomorphs are misinterpreted, that is).

Temnospondyls the early years (part II)

tetrapodzoology — Mon, 09 Jul 2007 06:01:07 +0000

Temnospondyls the early years (part II)

At last, I fulfill those promises of more temnospondyls. Last time we looked at the edopoids, perhaps the most basal temnospondyl clade: here we look at the rest of the basal forms. Scary predators, marine piscivores, late-surviving relics, and some unfortunate beasts burned alive in forest fires...

Studies on temnospondyl phylogeny mostly agree that 'post-edopoid' temnospondyls form a clade, the most basal members of which include Capetus, Dendrerpeton and Balanerpeton (Milner & Sequeira 1994, 1998, Holmes et al. 1998, Ruta et al. 2003a, b) [though some workers have found some of these taxa to be more basal than edopoids (Steyer et al. 2006)]. In contrast to the condition in edopoids, the interpterygoid vacuities of 'post-edopoids' are rounded at their anterior ends, the jugal (the bone that forms the cheek region) is shortened, and the configuration of skull bones is overall less archaic and fish-like.

Among these basal 'post-edopoids', Dendrerpeton (from the Upper Carboniferous of Nova Scotia and Ireland) had a rather large skull with laterally facing orbits, a short body, and well-developed, robust limbs. It lacked lateral line canals and grew to c. 1 m. These features suggest that it was predominantly terrestrial (Holmes et al. 1998). Several species have been named (Milner 1996). Studies of a well-preserved, three-dimensional ear indicate that Dendrerpeton had a frog-like tympanum (ear drum) suited for the perception of airborne sounds (Robinson et al. 2005). This discovery provides support for the idea that lissamphibians descend from temnospondyls (a subject we'll come back to much later), and indicates that at least some basal temnospondyls were listening to noises. But what were they listening to? Were they vocalizing, perhaps during the breeding season? It's previously been argued that the temnospondyl stapes was too massive to support a tympanum (see Laurin & Soler-Gijón 2006), so note that we have to be cautious in inferring the presence of a tympanum in all temnospondyls.

The Canadian Dendrerpeton specimens come from the famous Joggins Tree Stump Locality where the fossils of several tetrapod taxa (and the earliest land snails) have been discovered inside the hollowed trunks of lycopsid trees. It used to be thought that the animals had fallen into these natural traps and eventually died there of starvation, but the presence of abundant charcoal within the deposits now raises the possibility that the animals were taking refuge from forest fires, and that at least some of these unfortunate creatures were roasted alive (Falcon-Lang 1999, Scott 2001) [the adjacent picture depicts the early reptile Hylonomus, trapped in a hollow tree stump and about to be killed as a forest fire advances overhead].

Another basal temnospondyl is Balanerpeton woodi from the Viséan of East Kirkton in Scotland, a famous locality that has yielded a phenomenal diversity of Carboniferous invertebrates, fishes and early tetrapods. With a length of about 50 cm, Balanerpeton was superficially like a big salamander but it was odd in that, while the 40-42 teeth lining each half of the upper jaw were small, the 25-30 in each half of the lower jaw were much longer. The absence of lateral line canals, ossified wrist and ankle bones, and the apparent presence of eyelids indicate that it also was a terrestrial animal, although its larvae were aquatic (Milner & Sequeira 1994) [Balanerpeton skeletal reconstruction and life restoration immediately below is from Milner & Sequeira (1994), and borrowed from here].

Also somewhere around the base of Temnospondyli was Capetus palustris from the famous Upper Carboniferous Nýřany* desposits of the Czech Republic: this is one of the richest Upper Carboniferous fossil sites in the world, yielding at least 700 tetrapod fossils, discovered from the 1870s onwards. Previously, Capetus was regarded by some authors as an edopoid, close either to Edops or to the cochleosaurids, but recent studies have shown that it is not an edopoid, being closer to Balanerpeton (Steyer et al. 2006).

* Thanks to Greg Morrow for supplying the html need to produce a caron (wedge or inverted circumflex).

Capetus was a fairly scary looking, broad-headed predator with a deep posterior lower jaw: its skull was about 40 cm long, suggesting a total length of c. 1.5 m. As Sequeira & Milner (1993) noted, this makes Capetus one of the largest tetrapods in the Nýřany assemblage. Its teeth were mostly subconical, but those in the anterior part of the lower jaw seem to have been slightly laterally compressed, and possibly with weakly developed keels. As is the case in edopoids and some other basal temnospondyls, its skull bones lack lateral line canals. Sequeira & Milner (1993) suggested that Capetus was an alligator-like amphibious predator specializing on slow-moving tetrapod prey, and that it exploited a different lifestyle from that pursued by its contemporaries, the cochleosaurid Cochleosaurus, and the baphetids Baphetes and Megalocephalus. It was apparently rare in the fauna, with only eight fossils out of 700 from the Nýřany assemblage belonging to this taxon [the life restoration at the top of the article depicts Capetus. As is always the case with Palaeozoic tetrapods, life restorations of the animals being discussed here are few and far between (see previous lamentations on aetosaurs), so I had to resort to knocking one up myself. It's not bad, but it's not good either. Freely available for use, so long as Tet Zoo is credited].

Among the most surprising of the basal temnospondyls is the recently described Saharastega moradiensis from Niger. The big deal is that - while Saharastega is apparently way down near the base of Temnospondyli (and hence close to the Carboniferous taxa Balanerpeton and Capetus) - is it from the Upper Permian Moradi Formation, and hence was very much a 'late-survivor', hanging on for long, long after other basal forms had bit the dust. As we saw in the edopoid article, the Moradi Formation seems to contain a strongly provincial, relictual fauna. Saharastega had a fairly nondescript, flattish and subtriangular skull with widely separated and laterally-facing orbits located close to the skull margins. The tabular horn - a pointed projection, growing from the tabular bone at the rear corner of the skull - was particularly odd in this taxon in being directed laterally, rather than posteriorly, and the jaw joint was positioned unusually anteriorly. These peculiarities suggest that Saharastega was doing something interesting, but we don't know what that was. Although originally argued to belong to Edopoidea (Sidor et al. 2005), restudy has shown it to be outside of this clade (Steyer et al. 2006) [adjacent image shows Christian Sidor with Saharastega skull].

Another basal temnospondyl, the Upper Carboniferous Spanish taxon Iberospondylus schultzei, is interesting in that it was discovered in sediments deposited in coastal marine waters (Laurin & Soler-Gijón 2001, 2006). In contrast to the taxa we've looked at so far, it possesses lateral line canals, and therefore was very likely to have been aquatic (though we'll return later to how reliable lateral line canals are in demonstrating aquatic habits). Furthermore, the articulated condition of one of the specimens indicates that little post-mortem transport had occurred, so Iberospondylus was local to the environment in which it was preserved. It's been known for some time that at least some temnospondyls were marine animals (and we'll look at these other marine temnospondyls in a later post), but the basal position of Iberospondylus within temnospondyl phylogeny suggests that members of the group were able to inhabit the marine environment very early on in the group's history. As Laurin & Soler-Gijón (2001) argued, there are indications that this might have been true of even more basal tetrapods: if so, this would explain how Devonian tetrapods became near-globally distributed so early on in their evolution [Iberospondylus skull shown in adjacent image].

This ends our look at the most basal members of Temnospondyli - or, at least, it does according to the phylogenetic schemes I've decided to follow. You will note that at least some of these animals, including the edopoids, Dendrerpeton and Balanerpeton, were apparently terrestrial or mostly terrestrial. It is inferred that a total length of perhaps 40 cm or so was primitive for the group, but a size of 1.5 m or more was evolved within Edopoidea, and also exhibited by broad-skulled Capetus. Some basal temnospondyls were aquatic, and even marine, and some hung on until as late as the Late Permian: about 40 million years longer than we'd thought prior to 2005.

Later, more 'advanced' temnospondyls can be imagined to form a 'higher temnospondyl' clade and, when we come back to temnospondyls in the future, it's members of this group that we'll be looking at.

Refs - -

Falcon-Lang, H. J. 1999. Fire ecology of a Late Carboniferous floodplain, Joggins, Nova Scotia. Journal of the Geological Society, London 156, 137-148.

Holmes, R. B., Carroll, R. L. & Reisz, R. R. 1998. The first articulated skeleton of Dendrerpeton acadianum (Temnospondyli, Dendrerpetontidae) from the lower Pennsylvanian locality of Joggins, Nova Scotia, and a review of its relationships. Journal of Vertebrate Paleontology 18, 64-79.

Laurin, M. & Soler-Gijón, R. 2001. The oldest stegocephalian from the Iberian Peninsula: evidence that temnospondyls were euryhaline. Comptes Rendu de l'Academie des Sciences Paris, Science de la vie 324, 495-501.

- . & Soler-Gijón, R. 2006. The oldest known stegocephalian (Sarcopterygii: Temnospondyli) from Spain. Journal of Vertebrate Paleontology 26, 284-299.

Milner, A. R. 1996. A revision of the temnospondyl amphibians from the Upper Carboniferous of Joggins, Nova Scotia. Special Papers in Palaeontology 52, 81-103.

- . & Sequeira, S. E. K. 1994. The temnospondyl amphibians from the Visean of East Kirkton, West Lothian, Scotland. Transactions of the Royal Society of Edinburgh: Earth Sciences 84, 331-361.

- . & Sequeira, S. E. K. 1998. A cochleosaurid temnospondyl amphibian from the Middle Pennsylvanian of Linton, Ohio, U.S.A. Zoological Journal of the Linnean Society 122, 261-290.

Robinson, J., Ahlberg, P. E. & Koentges, G. 2005. The braincase and middle ear region of Dendrerpeton acadianum (Tetrapoda: Temnospondyli). Zoological Journal of the Linnean Society 143, 577-597.

Ruta, M., Coates, M. I. & Quicke, D. L. J. 2003a. Early tetrapod relationships revisited. Biological Reviews 78, 251-345.

- ., Jeffery, J. & Coates, M. I. 2003b. A supertree of early tetrapods. Proceedings of the Royal Society of London B 270, 2507-2516.

Scott, A. C. 2001. Roasted alive in the Carboniferous. Geoscientist 11 (3), 4-7.

Sequeira, S. E. K. & Milner, A. R. 1993. The temnospondyl amphibian Capetus from the Upper Carboniferous of the Czech Republic. Palaeontology 36, 657-680.

Sidor, C. A., O'Keefe, F. R., Damiani, R., Steyer, J. S., Smith, R. M. H., Larsson, H. C. E., Sereno, P. C., Ide, O. & Maga, A. 2005. Permian tetrapods from the Sahara show climate-controlled endemism in Pangaea. Nature 434, 886-889.

Steyer, J. S., Damiani, R., Sidor, C. A., O'Keefe, R., Larsson, H. C. E., Maga, A. & Ide, O. 2006. The vertebrate fauna of the Upper Permian of Niger. IV. Nigerpeton ricqlesi (Temnospondyli: Cochleosauridae), and the edopoid colonization of Gondwana. Journal of Vertebrate Paleontology 26, 18-28.

tetrapodzoology Mon, 07/09/2007 - 02:01

Tags

herpetology

Palaeozoic tetrapods

Categories

Life Sciences

Ahh, I was wondering why Saharastega did not feature in the edopoid post. It is a most puzzling creature indeed. Personally, and with all due respect to Seb Steyer and Ross Damiani, who are both colleagues and good friends, I doubt that it is a temnospondyl at all. Those laterally directed, downturned, deep tabular horns are strongly reminiscent of another Palaeozoic an-amniote. As indeed are the lateral placed eyes and the hugely broad interorbital skull roof and the supraoccipital bone. I speak of Seymouria, one of the few Palaeozoic an-amniotes to actually feature regularly in popular literature. Saharastega does have the typical temno-like interpterygoid vacuities but so does the russian seymouriamorph Kotlassia. So i think (like Nigerpeton) Saharastega may be a late-surviving southern extension of an otherwise early Permian Laurasian group. I wonder others think.

cheers

Adam

From this site:

Ř Ř Latin Capital Letter R With Caron (Capital R Hacek)
ř ř Latin Small Letter R With Caron (Small R Hacek)

Just a few notes...

- There is no point in citing Ruta et al. (2003b): it's a supertree, it doesn't tell us anything new. Have you seen their 2007 paper, though?
- Thus spake the mighty Robert L. Carroll in 1964 (p. 187): "Dissorophus multicinctus [an Early Permian terrestrial temnospondyl] has the parasphenoid partially fused to the base of the stapes. This situation also prevails in Eryops and Edops." Fused! :-o Deaf as a salamander, I say -- and that without the unique and deeply bizarre "otic flange" of Iberospondylus that closes the otic/spiracular channel.
- The point of Laurin & Soler-GijÃ³n is that intolerance of saltwater is a unique derived feature of Lissamphibia (or some larger clade), while tolerance (as seen in amniotes, temnospondyls, and Tulerpeton, and probably Ichthyostega also) is normal. Traditionally temnospondyls and everything else since the origin of digits were usually considered freshwater animals because "they were amphibians", to the point that sometimes accompanying fauna like xenacanthids was considered to have lived in freshwater simply because temnospondyls were found at the same site.
- If Capetus was an alligator-like predator, why does it lack lateral-line canals? The crocodiles have gone to the trouble of evolving their own analogous organs. Surprising as it is (in the presence of the more likely terrestrial near-amniote Solenodonsaurus), Capetus must have been more terrestrial than that, or I have overlooked something big... It doesn't happen to have an unusually smooth skull, does it?
- HTML code? Can you input the Unicode number instead? Test:
Å (copied from the Windows character table)
&U+0159; (Unicode number between HTML symbols)
I wrote this post after changing the coding in which I viewed the webpage to "Unicode (UTF-8)".
- Baphetes, and Sequeira 1994. :-]

Okay, so if you put a modern amphibian into salt water osmosis will dry the poor critter out, causing a painful death. Was there enough of a difference in ocean salinity to account for ancient marine amphibians, or is it more likely that they had adaptations that allowed them to absorb water and shed salt?

Thanks Greg and Dave. Do you think other scienceblogs enjoy peer review? :)

The alligator analogy for Capetus was based on skull shape I think. Note that the Capetus in my crappy drawing is doing its hunting on land. It doesn't have smooth skull bones, but strongly sculpted ones. Well said on stapes anatomy and saltwater tolerance. Note that even lissamphibians aren't as saltwater intolerant as you might think - there being at least some anurans that frequent, and breed in, brackish water. Large Bufo toads that live on beaches have been reported to swim in the sea. Plus anuran phylogeny shows us that even lissamphibians have made multiple over-water dispersals in their history (by rafting, not swimming of course).

And why did I cite supertree studies? Because I choose to, Agent Smith.

Only just saw Adam's post (went into the junk folder for the usual mysterious/unknown reason). Wow.. or, yikes - surely not. That is interesting - unfortunately we only have their brief Nature paper to go on right? Steyer et al. (2006) refer to a 'Damiani et al. in press' JVP paper that monographs Saharastega: I haven't yet seen this, does anyone know if it's out? I don't know as the last two issues of JVP have yet to arrive here at Tet Zoo towers (and yes, I have made inquiries about this).

Ross Damiani, Christian A. Sidor, J. Sébastien Steyer, Roger M. H. Smith, Hans C. E. Larsson, Abdoulaye Maga, and Oumarou Ide: The vertebrate fauna of the Upper Permian of Niger. V. The primitive temnospondyl Saharastega moradiensis, JVP 26(3), 559 -- 572 (11 September 2006)

Abstract:
"The skulll of the temnospondyl amphibian Saharastega moradiensis, from the Upper Permian Moradi Formation (Izégouandane Group, Izégouandane Basin) of northwestern Niger, is described in detail. Saharastega moradiensis is the most primitive known temnospondyl from Gondwana and possesses a combination of plesiomorphic and apomorphic character states, which suggest affinities with the Edopoidea, a clade of basal temnospondyls from the Upper Carboniferous and Lower Permian of Euramerica. These include the exclusion of the lacrimal from the orbital margin, the exclusion of the vomers and palatines from the interpterygoid vacuities, and the presence of an intertemporal ossification. Autapomorphies of the new taxon include the presence of narrow and elongated, transversely oriented nostrils; an extensive tongue-and-groove contact between the premaxillae and maxillae; tabulars that possess exceptionally large, laterally and ventrally directed 'horns'; and an extraordinary 'occipital plate' that may be formed, at least in part, by a supraoccipital ossification. A phylogenetic analysis of select Paleozoic temnospondyls indicates that S. moradiensis is the sister taxon to the edopoids, represented in this analysis by Chenoprosopus and Edops. This suggests that S. moradiensis represents a late-surviving member of a clade that is the sister group [sic] of the Edopoidea. Members of this clade may have been restricted to equatorial northwest Africa during the Late Carboniferous and Early Permian, an area that was not affected by the extensive glaciation that covered much of southern Pangea."

The outgroups are Greererpeton and Proterogyrinus; the ingroup consists only of temnospondyls.

I get JVP about a month after it appears, and the Austrian mail is extremely slow...

I wrote:

Å (copied from the Windows character table)

This displays correctly when I view the page as Unicode, but not when I view it as "Western European (ISO-8859-1)".

Oddly, Greg Morrow's post displays correctly both ways.

Darren: Your Capetus is pretty good as it manages to look like an entirely plausible animal that doesn't seems off balance or otherwise just plopped on the page.

I may not know temnospondyls by I know what I like.

Hey, it's my old boss Chris Sidor! He should be back from Tanzania tomorrow. I remember seeing the Saharastega holotype in a drawer when I was inventorying. Not being a theropod, it couldn't get me _too_ excited... ;)

Crassigyrinus, or... How I'd love a giant killer Carboniferous tadpole for a pet

tetrapodzoology — Wed, 04 Jul 2007 16:01:30 +0000

Crassigyrinus, or... How I'd love a giant killer Carboniferous tadpole for a pet

Today I submitted another one of those long-delayed manuscripts. Yay. I also got to work preparing one of the three conference talks I'm supposed to be giving this year - how the hell I'm going to pull off all three I'm not sure. Anyway, leaving well alone the whole picture-of-the-day debacle, it's time for a proper post. Last time we looked at the edopoids, one of the most basal clades of temnospondyls, and in the next post I plan to write about some of the other basal temnospondyls.

Ever trying to recycling old text that sits, un-used, on disks, drives and memory-sticks, here I'm going to avoid temnospondyls, yet stay within the world of Palaeozoic tetrapods. We're going to look at one of the most peculiar and mysterious of tetrapods from its time: the bizarre Crassigyrinus scoticus - a large freshwater predator shaped something like a giant tadpole...

Crassigyrinus was a truly bizarre animal, known only with certainty from sediments deposited in ponds and lakes of Early Carboniferous Scotland (Godfrey (1988) reported a possible specimen from Greer, West Virginia). During the Carboniferous, Scotland was near to the equator and covered with swamps and lakes that were inhabited by diverse fishes and tetrapods. These included the giant swimming anthracosaur Proterogyrinus, snake-like aïstopods, and small, terrestrial temnospondyls. Large scorpions, eurypterids and millipedes were also present.

Crassigyrinus is all but absent from textbooks published prior to 1990, so you might think that it's a new discovery. But that's not so: the first good specimen (a partial skull) was collected in the 1850s by the famous Scottish geologist, journalist, social campaigner and folklorist Hugh Miller (1802-1856). This wasn't officially named and described until 1929 however when David M. S. Watson (1886-1973) described and named it: the specimen consisted only of the lower half of the skull, and Watson mistakenly thought that Crassigyrinus was shallow-skulled, hence the generic name he chose (Crassigyrinus means 'shallow wriggler', or something like that). During the 1970s and 80s, two additional specimens were discovered (the skull of one of these is shown, in dorsal view, in the adjacent image: borrowed from here). The most exciting of these was a nearly complete skeleton discovered near Fife by Stan Wood, a well known professional fossil collector. This specimen provided much new information on the body of this bizarre beast, revealing its tiny limbs and primitive spinal column for the first time. We also now know that the skull of Crassigyrinus, while long, was not really shallow.

Macromerium scoticum, named in 1890 for a lower jaw from the same locality as the more recently discovered Crassigyrinus specimens (Lydekker 1890), is now regarded as the type specimen of Crassigyrinus (Panchen 1985), despite previous arguments that it was quite different and more likely to belong to a baphetid (the generic name Macromerium is not available for Crassigyrinus as the type species belongs to an anthracosaur [I think]). Anyway, the reason that Crassigyrinus only appears in textbooks post-1990 is that 1990 is the year when the first good life restoration was published.

Crassigyrinus was long-bodied, with a large, blunt-nosed head equipped with huge eyes and a ferocious array of teeth. Thickened bony ridges ran along the dorsal midline of the snout and between the eyes, and it is inferred that they helped the skull to withstand stress when the animal bit prey. Its massive palatal teeth and wide gape (it could probably open its jaws as wide as 60º) further suggest that it was a powerful predator with a strong bite. Its peculiar stunted forelimbs were tiny and the humerus was only 35 mm long (the whole animal was about 1.5 m long). Various foramina on the humeral surfaces recall those seen in Ichthyostega, Acanthostega and lobed-finned fishes like Eusthenopteron (Panchen 1985, 1991). The hindlimbs were much larger than the forelimbs, and in the pelvis the ilium lacked a bony connection to the vertebral column (a classic feature of aquatic tetrapods). The tail is unknown but is assumed to have been long and laterally compressed.

Crassigyrinus has often been argued to combine a perplexing array of fish and tetrapod features, with the result being that its phylogenetic affinities have proved controversial. However, our views on how fishy it was have changed in recent years, as claims that it possessed several bones not normally seen in tetrapods - including a preopercular at the back of the skull and an anterior tectal and lateral rostral near the nostril - now seem erroneous (Clack 1998). The bones identified as anterior tectals and lateral rostrals seem instead to be misplaced, misinterpreted nasals and vomers.

It's not just the bones of the nasal region that have proved problematical, but the nostril and its supposed associated openings as well. Three Crassigyrinus skulls are now known, but for a long time there was just the Hugh Miller specimen, and this was always somewhat confusing as it seemed to have two nostril openings. Panchen (1967) argued that the lower of the two - the one closer to the edge of the mouth - was the true nostril, and he also thought that it was continuous with a groove that connected this opening with the jaw margin (which would then make this groove a nasolabial groove). However, he later regarded the lower opening as some sort of sensory structure (Panchen & Smithson 1990), and this explains why the most oft-reproduced life restoration of Crassigyrinus - an excellent stippled drawing produced by Michael Coates* - equips Crassigyrinus with a barbel located at the same place as the supposed sensory pit (see above for that pic: borrowed from here).

* Whom, thanks to Carl Zimmer, I always associate with Spot the dog (Zimmer 1998).

Alas, it was not to be. Clack (1998) described how further examination of both the original specimen and one of the new ones demonstrated how the supposed sensory pit was merely an artifact of preservation; not a real anatomical feature. No barbels in Crassigyrinus, no second nostril, no nasolabial groove [psst - want to know more about stem-group tetrapods? Then buy Clack (2002), shown in adjacent pic].

At the back of the skull, prominent notches just behind the eyes might once have been interpreted as having accommodated ear drums. However, it now seems that in many stem-group tetrapod lineages, these notches actually housed spiracles (small remnants of the gill system), and it is likely that this was their function in Crassigyrinus (Panchen 1985, Clack 2002).

The huge eye sockets of Crassigyrinus were diamond-shaped, and placed quite high up on the skull and close together. The inferred large size of the eyes suggests that it was able to see well in dark or murky water. Its cheek region bears canals that presumably housed a lateral line system and a distinctive sort of surface ornament on its skull bones suggested to Clack (1998) that it might have had weed-mimicking skin flaps like those seen on matamatas and wobbegongs. These have yet to be shown in any life restoration, with the exception of a yet-to-be-published piece that I advised [clue: it's in Tom Holtz's new dinosaur encyclopedia]. A bowl-shaped depression - the interpremaxillary fenestra - connected the dorsal surface of the snout tip with the palate, but it doesn't serve any obvious function except as an exit point for an enlarged dentary fang pair: another tetrapod where teeth from the lower jaw pierce the skull roof. Special notches on the lower jaws seem to have housed the enlarged palatal fangs.

The rest of the skeleton of Crassigyrinus is quite primitive in many details. Its vertebrae are simple and lack enlarged interlocking processes (zygapophyses), and the back of its skull does not have the distinct ball-shaped component called the occipital condyle. However, this is thought not to be a primitive character (because a properly formed occipital condyle is present in many fishes), but a paedomorphic one (Panchen 1991). The ribs, while well-developed, lack distinct facets for articulation with the vertebrae, and hence also appear primitive or degenerate compared to those of most other tetrapods. A consequence of this combination of features is that Crassigyrinus has even been regarded by some as the most primitive of tetrapods*, or even as a non-tetrapod: Panchen (1991) reported this (and contested it), noted that 'it is a tetrapod, contrary to the opinion of some of our colleagues' (p. 116). The idea that Crassigyrinus was a late-surviving relict was considered by Ahlberg & Milner (1994) who noted that 'Instead of being the first tetrapod to 'return to the water', [Crassigyrinus] may be the last survivor of the primitive tetrapods that never left the water' (p. 512).

* Incidentally, there are two different understandings of the term Tetrapoda: the conventional/traditional version - the one I use here at Tet Zoo - and the crown-group version, where Tetrapoda in the conventional sense is replaced by Stegocephali. Guess which I prefer. No time to discuss this now.

However, new evidence from other Carboniferous tetrapods, and new phylogenetic studies, have shown that Crassigyrinus is more likely to have been secondarily primitive, rather than a basal relict: it was fairly close to the base of Tetrapoda, but its alleged fish-like characters are either erroneous or secondarily reacquired. It also used to be argued (e.g. Panchen & Smithson 1988) that Crassigyrinus was close to the anthracosaurs and perhaps more closely related to amniotes* than to stem-group tetrapods, but the evidence used to support this is generally regarded as erroneous nowadays. Because of its uniqueness, Crassigyrinus has at times been given its own special new taxonomic groups: Panchen (1973) made it the sole member of a new 'family', Crassigyrinidae, within its own 'order', Palaeostegalia [adjacent life restoration by M. Collins borrowed from here. Note the barbel].

* Amniota is the tetrapod clade that includes synapsids and reptiles, and hence excludes all the tetrapods that used to be called 'amphibians'.

How did Crassigyrinus live? Compared by various authors to moray eels, amphiumas and sirenids, it perhaps lurked among waterweed and submerged branches, remaining concealed, partly thanks to its weed-like skin flaps. It would have detected prey with its huge eyes and lateral line system and, bursting from cover with undulations of its tail and body, it would have grabbed fishes and other animals with its deep, toothy skull. Large fangs allowed it to keep hold of slippery prey and it could open its jaws extremely wide to grab and swallow large prey. Crassigyrinus was probably a major predator of smaller vertebrates and may have been one of the dominant predators in its environment. Its proportionally tiny limbs indicate that it was unable to move on land. All in all - a pretty surreal Carboniferous beast, and I wish we knew more about it.

Finally.. what's with the picture at the top? I recently learnt that the Impossible Pictures series Prehistoric Park (which, like Primeval, kinda went under my radar) included an episode where Nigel Marven captured a live Crassigyrinus. Oh.

Refs - -

Ahlberg, P. E. & Milner, A. R. 1994. The origin and early diversification of tetrapods. Nature 368, 507-514.

Clack, J. A. 1998. The Scottish Carboniferous tetrapod Crassigyrinus scoticus (Lydekker) - cranial anatomy and relationships. Transactions of the Royal Society of Edinburgh: Earth Sciences 88, 127-142.

- . 2002. Gaining Ground: the Origin and Evolution of Tetrapods. Indiana University Press, Bloomington and Indianapolis.

Godfrey, S. J. 1988. Isolated tetrapod remains from the Carboniferous of West Virginia. Kirtlandia 43, 27-36.

Lydekker, R. 1890. On two new species of labyrinthodonts. Quarterly Journal of the Geological Society, London 46, 289-294.

Panchen, A. L. 1967. The nostrils of choanate fishes and early tetrapods. Biological Reviews 42, 374-420.

- . 1973. On Crassigyrinus scoticus Watson, a primitive amphibian from the Lower Carboniferous of Scotland. Palaeontology 16, 179-193.

- . 1985. On the amphibian Crassigyrinus scoticus Watson from the Carboniferous of Scotland. Philosophical Transactions of the Royal Society of London B 309, 505-568.

- . 1991. The early tetrapods: classification and the shapes of cladograms. In Schultze, H.-P. & Trueb, L. (eds) Origins of the Higher Groups of Tetrapods, Controversy and Consensus. Comstock/Cornell University Press (Ithaca and London), pp. 110-144.

- . & Smithson, T. R. 1988. The relationships of the earliest tetrapods. In Benton, M. J. (ed) The Phylogeny and Classification of the Tetrapods, Volume 1: Amphibians, Reptiles, Birds. Clarendon Press (Oxford), pp. 1-32.

- . & Smithson, T. R. 1990. The pelvic girdle and hind limb of Crassigyrinus scoticus (Lydekker) from the Scottish Carboniferous and the origin of the tetrapod pelvic skeleton. Transactions of the Royal Society of Edinburgh, Earth Sciences 81, 31-44.

Zimmer, C. 1998. At the Water's Edge: Macroevolution and the Transformation of Life. Free Press, New York.

tetrapodzoology Wed, 07/04/2007 - 12:01

Tags

herpetology

Palaeozoic tetrapods

Categories

Life Sciences

"Incidentally, there are two different understandings of the term Tetrapoda: the conventional/traditional/total-group version ... and the crown-group version...."

I don't see too many people use it as a total group (i.e., everything closer to crown-tetrapods than to lungfish). Rather, it seems to me that most people use it as a crown group or as an apomorphy-based clade, based on the presence of "feet". (Whatever, exactly, "feet" are.)

More discussion here: http://www.phylonames.org/forum/viewtopic.php?t=17

[from Darren: oh yeah, thanks for correction. Will ammend text accordingly]

Nice post! Explains why it seemed to me that every book I read that mentioned C. seemed to hang it on to a different branch of the family tree! Secondarily aquatic (with features acquired by pedomorphism) sounds like an excellent recipe for taxonomic difficulty.

First Temnospondyls, than Crassigrynus. To quote Stimpy: Happy happy, joy, joy :-)!

BTW, sorry for spoiling the paca episode :(, but then I always thought we were supposed to find the sea lion photo on your flickr site ...

BTW, sorry for spoiling the paca episode :(

It's ok, I forgive you :) My fault for not choosing a more obscure image.

Crassigyrinus always fascinated me, especially the strange proportions with those giant eyes and the tiny forelimbs. The reduction of the forelimbs is really interesting, as it seems that the reduction of the hindlimbs is often prefered in evolution. It´s sad to read that the tentacle on the snout didn´t exist, it made it even stranger. In overall shape (especially with the old picture which show a tentacle) it looks a bit catfish-like, not only cause of the body shape, but also cause of the giant mouth. It is also still on my to-do-list for sculptures, I hope I will manage to make once a model of it. My current project, a Blainville´s beaked whale awaits still finishing.

"secondarily primitive" -- what a great phrase!

I go along with the dual belief that it was a left over from the more basal tetrapods, but was showing a degeneration of numerous traits as well. Sorta-like an Acanthostega descendant going all caecilian on you...

Large scorpions, eurypterids and millipedes were also present.

As soon as you leave the tetrapods, British understatement comes back, eh?

(Crassigyrinus means 'shallow wriggler', or something like that)

I thought "thick tadpole"?

I bet there are not enough tooth rows in the lower jaw in the top picture, BTW...

I thought "thick tadpole"?

Oh yeah, how stupid of me (even I know that anything 'crassi-' means thick). I wondered where I got 'shallow wriggler' from, but had a recollection of reading it in Clack's excellent Gaining Ground: yup, there it is on p. 205. Hmm.

Aquatic form with rear legs much less reduced than forelimbs. That sounds familiar. Some Archaeoceti are similar. In that case it has been hypothesized that the rear limbs were used during mating, could that apply to Crassigyrinus too?

Huge head, powerful jaws, tiny forelimbs? Sounds like an aquatic abelisaur!

*waits for stifled laughter*

Awesome post, though, Darren. Crassigyrinus certainly throws a wrench into the already-sketchy phylogeny of early tetrapods, which is a debate I am fascinated by.

Incidentally, as I recall, Laurin argues that the crown group sense of Tetrapoda is the "traditional" sense. (I forget his exact points, though.) Perhaps it would be more fair to say you use an apomorphy-based definition rather than the crown group definition and leave it at that.

Incidentally, as I recall, Laurin argues that the crown group sense of Tetrapoda

No, he argues that in those cases when it can be told how most of the literature ( = mainly neontologists) uses it, that sense is usually the crown-group.

I think this includes many cases where people simply didn't care and used the same halfway widely known name for several nested clades, but I haven't checked.

> It would have detected prey with its huge eyes and lateral line system

Electroreception might have been useful for detecting prey and/or avoiding obstacles in muddy water, too. The electroreceptive sense is usually associated with the lateral organ in modern fishes, and the lateral line system was also present in many basal tetrapods. Is there any evidence for the presence of electroreceptive or electrogenic organs in basal tetrapods?

[from Darren: electroreception is thought to have occurred in aquatic seymouriamorphs, as they appear to possess electroreceptive organs on the skull bones. I haven't seen it advocated for other early tetrapods however]

from Darren: electroreception is thought to have occurred in aquatic seymouriamorphs, as they appear to possess electroreceptive organs on the skull bones. I haven't seen it advocated for other early tetrapods however

Apparently it's universal: the same paper that mentions the organs in Discosauriscus says salamander larvae have it, too. But no, it's not the same thing as the lateral-line organ, nor in the same places.

Evidence for electrogenic organs is absent, if we ignore one interpretation of the baphetid orbit expansion.

The Prehistoric Park (TM) Crassigyrinus model had the wobbegong-style webbing present on the facial area as-per Jenny Clack's direction. We had it toned down form whata wobbegong looks like 'cause it was difficult to scuplt, and animate. Overall, I felt we did a pretty good job on that sculpt... other than the forelimb being a little too big, but that was a miscommunication issue with the sculptors... the detail really showed up fully before colour was added.. really it was a shame the model got so little screen time, cause it kicked ass (and bit a chunk out of Nigel, even t-rex didn't manage that).

there was a really good promo pic taken of crassy in the water on its own, but it was never used.

Temnospondyls the early years (part I)

tetrapodzoology — Fri, 29 Jun 2007 09:00:21 +0000

Temnospondyls the early years (part I)

Like plethodontid salamanders, Wealden dinosaurs, and rhinogradentians, the remarkably successful and diverse tetrapods known as temnospondyls have been riding the Tet Zoo wagon right since the earliest posts of ver 1. But, to my shame, I've never gotten round to completing one of the ten or so posts that I plan to publish on them. If you're interested in tetrapod evolutionary history and haven't heard of temnospondyls before, it's time to get learning, as they were one of the most diverse, abundant and ecologically significant tetrapod groups of the Palaeozoic and early Mesozoic [adjacent pic shows random compilation of different temnospondyls, including the palate of the immense Brazilian archegosaurid Prionosuchus plummeri]. Furthermore, they survive to the present: if, that is, you agree with the conclusions of some experts...

It's easy to become frustrated with the fact that people aren't more familiar with the amazing diversity of Palaeozoic life: most people think that vertebrate evolutionary history begins and ends with dinosaurs, mammoths and Neanderthals, and it's always been a problem that so few sources provide an adequate overview of the diversity that existed before the dinosaurs. As a child it bugged me that the same few Palaeozoic animals were featured in every single prehistoric animal book, as if they were the only ones that ever existed: the lepospondyl Diplocaulus, the anthracosaur Pholiderpeton (then known as Eogyrinus), the seymouriamorph Seymouria, the diadectomorph Diadectes, and that most famous of temnospondyls, Eryops. In reality, these are just the tips of many icebergs. To make matters worse, those few temnospondyls that feature in the popular or semi-technical literature are consistently portrayed inaccurately, and that includes good old Eryops: take Maurice Wilson's painting shown below - nice painting, but not really an accurate depiction (neither morphologically nor ecologically).

So where do you go if you want to learn about the full and wondrous diversity of temnospondyls, or indeed of any Palaeozoic tetrapods? That's a very good question, as there just aren't readily accessible texts devoted to these animals. Publishers only want dinosaurs. Dinosaurs dinosaurs bloody dinosaurs, although Cenozoic mammals and pterosaurs have also been the subjects of a few recent non-technical volumes. A major revision of temnospondyls has recently appeared: Schoch and Milner's Handbuch der Paläoherpetologie volume (Schoch & Milner 2000). However, it only covers the stereospondyls, an advanced temnospondyl sub-group. Furthermore, like all volumes in the handbuch series, it is horrendously expensive (I did at least, once, see a copy).

Anyway, enough of the preamble. In this and future posts I'll be providing a group-by-group overview of temnospondyls, concentrating on those groups and taxa that are particularly interesting in terms of palaeobiology, evolution or life appearance. I am, obviously, not attempting a full technical review or anything, and if you're seriously interested in that sort of thing it's mandatory that you get hold of Schoch & Milner (2000) as well as a ton of the primary literature. Temnospondyl phylogeny still has its grey patches and areas of argument, but several studies have been devoted to analyzing the relationships of large chunks of the temnospondyl tree (e.g. Yates & Warren 2000) and supertree studies devoted to the phylogeny of Palaeozoic tetrapods have also incorporated temnospondyls (Ruta et al. 2003a, b), so we do have agreement on the main branching order.

What are temnospondyls? They're a tetrapod clade (traditionally - and erroneously - lumped together with several other groups in an assemblage termed the labyrinthodonts), and they're perhaps, but perhaps not, ancestral to extant lissamphibians (we'll come back to that issue later). Their closest relatives appear to be the Carboniferous baphetids and colosteids, and the Carboniferous-Permian anthracosaurs, and if you want to know more about those groups I'm afraid you'll have to want for quite a bit longer. Characteristic temnospondyl features include particularly large openings on the palate (termed interpterygoid vacuities), palatal tusks, a diamond-shaped interclavicle, scapulae that possess ornamented surfaces, and distinctive vertebrae and pelvic bones. Their most distinctive features - the interpterygoid vacuities - remain of unknown function (so far as I can tell from the literature). Lateral line canals on the skull bones of some species suggest that they possessed neuromasts: the specialised cells that fish use to detect pressure changes in water. The absence or presence of lateral line canals in temnospondyls have therefore been widely used to help inform guesses about lifestyle, but as we'll see when we get to some groups this is not always reliable. Note that modern amphibians (like the giant salamander shown below) are atypical compared to temnospondyls and other Palaeozoic forms in being naked-skinned: with a few exceptions, you should imagine temnospondyls and their kin as scaly. Again, more on this in the future.

Which phylogenetic definition should be favoured for Temnospondyli is a bit tricky, and I want to avoid that issue for now. They include terrestrial, amphibious and wholly aquatic forms, brackish-water and marine forms, small generalist predators, large and formidable super-newts, giant small-limbed pseudo-crocodiles, frog-headed lurkers, the famous tusked toilet-bowl heads [like gigantic Mastodonsaurus giganteus, shown in image above. That skull is 60 cm long], sail-backed and armoured forms.. and others. The smallest were less than 30 cm long; the biggest may have approached 10 m in length (Cox & Hutchinson 1991). They are so diverse that it is difficult to pick a representative member. While many lineages become devoted to life in water, others were strongly, or entirely, terrestrial.

We begin our tour with taxa right down at the base of the group. These animals mostly lived in the Carboniferous (some survived to as late as the Late Permian), at a time when the southern continents were clustered together deep in the south and partly covered by an ice cap, and a conjoined Europe and North America were located on the equator.

Often regarded as the most primitive temnospondyl group is Edopoidea (previously known as Edopsoidea). Unlike more advanced kinds they exhibited an archaic pattern of palatal bones, and still possessed various additional bones at the back of the skull. Edopoids also had particularly big premaxillae (the bones that form the tip of the snout) and proportionally small external nostrils. Within the clade, the most basal member seems to be Edops from the Lower Permian of the USA, a broad-skulled animal with large palatal teeth. It was fairly big, at 2 m in length. Fragmentary remains from the Viséan (one of the early sections of the Carboniferous) of Scotland appear to come from Edops or a close relative and hence predate the type Edops material of the Permian.

Cochleosaurids were long-snouted edopoids, ranging in length from c. 30 cm to perhaps 3 m, known from swamp and lacustrine habitats of Nova Scotia, Ohio, the Czech Republic, Ireland and Africa. Lateral line canals are absent (with one exception: read on), so they are thought to have been mostly terrestrial (although it is known that they produced aquatic gilled larvae). While their skulls are decorated by a sculpturing of pits and furrows, a distinctive feature of the group is that a zone along the skull midline is only lightly sculptured (Sequeira 1996, 2004, Milner & Sequeira 1998). Cochleosaurids might have been amphibious predators and they have typically been imagined as rather crocodile-like in basic lifestyle [life restoration of Cochleosaurus above from here]. The broader-skulled forms were perhaps similar to Edops in being amphibious ambush predators of fish and smaller tetrapods, while some of the more narrow-snouted cochleosaurids, like the cochleosaurine Chenoprosopus milleri, may have foraged on land for arthropods and small tetrapods. However, even Edops is interpreted as terrestrial by some workers (Schoch 2001, p. 341).

Nigerpeton, the only African cochleosaurid, is closely related to Chenoprosopus but is in many ways a highly unusual member of the group. It was gigantic compared to some of its relatives, with a long, flattened skull 45-56 cm long, and its lateral line system contrasts with their absence in other edopoids. Like many temnospondyls, Nigerpeton possessed particularly large fang-like palatal teeth as well as enlarged teeth in the lower jaw, but the degree of heterodonty it possessed is extraordinary: the teeth at its premaxillary tips were large, and tooth size then declined posteriorly before increasing again in the maxilla, before decreasing again further posteriorly. Particularly big fangs - bigger than those lining the jaws - were present in patches on parts of the palate, while huge fangs near the lower jaw tip fitted through special openings in the skull roof when the mouth was closed [in the adjacent image, the big holes near the snout-tip are not the nostrils (those are much further back), but are instead the openings for the fangs of the lower jaw]. Protruding lower jaw teeth are also seen in a much later group of temnospondyls, the mastodonsauroids (and are also present in some living crocodilians). These specialized teeth suggest that Nigerpeton was an effective carnivore, presumably capable of grabbing large tetrapods (Steyer et al. 2006). While other cochleosaurids are Carboniferous and from the Northern Hemisphere, Nigerpeton is unusual in being from the Upper Permian of Niger. Discovered alongside captorhinids, pareiasaurs, and the late-surviving basal temnospondyl Saharastega, Nigerpeton provides further support for the idea that Late Permian west African was home to a strongly endemic fauna (Sidor et al. 2005, Steyer et al. 2006).

Edopoids - perhaps the most basal temnospondyl clade we know of - therefore included mid-sized terrestrial and amphibious taxa as well as late-surviving big-toothed macropredators. And - already - we have we stop as I need to go get a haircut. Much much more on temnospondyls to come later, honest.

Refs - -

Cox, C. B. & Hutchinson, P. 1991. Fishes and amphibians from the Late Permian Pedra de Fogo Formation of northern Brazil. Palaeontology 34, 561-573.

Milner, A. C. & Sequeira, S. E. K. 1998. A cochleosaurid temnospondyl amphibian from the Middle Pennsylvanian of Linton, Ohio, U.S.A. Zoological Journal of the Linnean Society 122, 261-290.

Ruta, M., Coates, M. I. & Quicke, D. L. J. 2003a. Early tetrapod relationships revisited. Biological Reviews 78, 251-345.

- ., Jeffery, J. & Coates, M. I. 2003b. A supertree of early tetrapods. Proceedings of the Royal Society of London B 270, 2507-2516.

Schoch, R. R. 2001. Can metamorphosis be recognised in Palaeozoic amphibians? Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen 220, 335-367.

- . & Milner, A. C. 2000. Stereospondyli. Handuch der Paläoherpetologie, Teil 3B. Verlag Dr. Friedrich Pfeil, München.

Sequeira, S. E. K. 1996. A cochleosaurid amphibian from the Upper Carboniferous of Ireland. Special Papers in Palaeontology 52, 65-80.

- . 2004. The skull of Cochleosaurus bohemicus Fric, a temnospondyl from the Czech Republic (Upper Carboniferous) and cochleosaurid interrelationships. Transactions of the Royal Society of Edinburgh 94, 21-43.

tetrapodzoology Fri, 06/29/2007 - 05:00

Tags

herpetology

Palaeozoic tetrapods

Categories

Life Sciences

Wasn't Koolasuchus a temnospondyl? This would give the group a temporal range ending in the Cretaceous, as I recall.

[from Darren: yes, there are Jurassic and Cretaceous temnospondyls. Patience, patience...]

Yes, Koolasuchus is a temnospondyl. A real "living fossil" among dinosaurs. I believe there's another Cretaceous-age temnospondyl somewhere in the world (Asia?), so the group could have a significant post-Triassic history and we just haven't found them yet.

There is a very good book with the title "Saurier-Expedition in die Urzeit" by Rainer Schoch, which deals mainly with the actual special exhibition in the Löwentormuseum Stuttgart. There is also a big and very interesting part about early amphibians (and also many other prehistoric creatures you won´t find in most mainstream paleo-books), including several photos of the life-sized reconstructions in the museum.

*jumping with joy* :-)

The dots on the palatine and vomer of Prionosuchus... are they all denticles?

[from Darren: wait for the post :) ]

The Carboniferous doesn't have official 'Lower' and 'Upper' divisions: in order of youngest to oldest it is divided into the Tournaisian, Visï¿½an, Namurian, Westphalian and Stephanian.

Oh, here you're out of date by 3 years (at least): http://www.stratigraphy.org/gssp.htm

[from Darren: bugger]

What you list is the old western European scale. There are now an official Lower ( = Mississippian) and Upper Carboniferous ( = Pennsylvanian), the former consisting of Tournaisian, Visï¿½an, and Serpukhovian, and the latter comprising the Bashkirian, Moscovian, Kasimovian, and Gzhelian. In other words, the marine parts of the western European and Russian Carboniferous have become the basis for the official scale.

The Bashkirian-Moscovian boundary coincides with the Westphalian B-C boundary, IIRC.

and its lateral line system contrasts with their absence in other edopoids.

Careful: lateral-line canals on skull bones only work one way as evidence. In extant lissamphibians that have lateral line organs, they always stay in the skin and don't leave traces on the bones. How sculptured are edopoid skulls?

[from Darren: we're only talking here about osteology, though good point]

I believe there's another Cretaceous-age temnospondyl somewhere in the world (Asia?)

Not that I've heard of. Large numbers of Jurassic temnospondyls have been found in Asia, though (all within the last 20 years).

Oh if only you could have posted this before my finals - my attempted essay on temnospondyls suffered from a complete memory blank!

"Furthermore, they survive to the present: if, that is, you agree with the conclusions of some experts..."

Crap. It's 1:35am and I read that and know I have to read past the fold. Your posts are demanding reading but contain too much cool stuff to put off 'til tomorrow.

BTW, there's a copy of Schoch and Milner's Handbuch der Paläoherpetologi volume on ABEBOOKS.COM for a mere 125USD.

Cladistics is good, science advances, paleontology is better and more interesting, but... When I was a kid (school in 1950s and 1960s) there were a bunch of animals we could call "Paleozoic amphibians," and NOW THERE IS NO SHORT WAY TO REFER TO THEM COLLECTIVELY!

But a couple of suggestions for anyone who wants to get STARTED on learning about them: REALLY introductory stuff so you can appreciate Darren's more detailed posts:
---on the WWWeb, there are a bunch of good pages at Toby White's Palaeos.com
---book designed to appeal to both academic and popular markets: Jenny Clack's "Gaining Ground" (Indiana Univ. Press)-- it's maybe more about the earliest tetrapods than about advanced temnospondyls, and not much on taxonomic survey, but a good introduction to the biology of those Paleozoic lower tetrapods I used to have a name for.

I remember years ago try to find out if there was a marine Paleozoic "amphibian" (with no luck) as I always thought I strange that such an aquatic group never entered the sea - but now you tell us there are marine temnospondyls - thanks for answering one of my very old questions :)

Also I remember seeing the skull in the 3rd picture down in Germany and being baffled by a tooth from the lower jaw emerging out of the top of the skull!

The "Palaeontology" volume of the "Amphibian Biology" series has decent reviews of temnospondyls, among many other groups. The volume isn't cheap, but its price is alot better than the Handbuch series.

When I was a kid (school in 1950s and 1960s) there were a bunch of animals we could call "Paleozoic amphibians," and NOW THERE IS NO SHORT WAY TO REFER TO THEM COLLECTIVELY!

Actually... did you really ever want to refer to Eryops and Brachydectes at the same time? :-)

(Brachydectes is almost all that taxonomic revisions have left of the Lysorophia. Those animals -- a lepospondyl group; the closest relatives of the lissamphibians according to Michel Laurin and some of his students -- seem to have been eels for all practical purposes, though with tiny legs and presumably lungs.)

David - I suspect that Allen more had in mind things such as Ichthyostega, Diplocaulus and Eryops (though, ok, any collective term for those taxa would have to include lysorophians as well). One could argue that the fact that there was a catch-all term for these many groups - be it labyrinthodonts or the old (not Laurin-esque) version of Stegocephalia or whatever - actually masked and obscured diversity, a bit like 'dinosaur' is used by some lay-people for every vertebrate from the pre-Holocene Phanerozoic.

By the way: the next post is on Crassigyrinus, hopefully with more temnospondyls after that.

Cool! Crassigyrinus is awesome. :-)

(For the record: I don't like Michel's definition of Stegocephali at all. But there are too few contributors to the companion volume of the PhyloCode to prevent it from going through, it seems.)

To answer my own question: "The skull roof has a densely pitted surface and lacks any traces of lateral line sulci" in Edops craigi (ref p. 321). That ought to mean that the skin was directly attached to the skull like in crocodiles, probably leaving no space for a lateral-line organ. "Its occurrence and distribution" (same page) suggest a "semiterrestrial" way of life, too.

Rainer R. Schoch (2002/12/15): The evolution of metamorphosis in temnospondyls, Lethaia 35:309327.

The article (here) says these temnospondyl impressions point towards naked skin?

What say ye?

The scales are in the dermis, so they won't show up in any but the most detailed skin impressions. They are "fish"- and caecilian-type scales, not "reptile"-type scales (which are thickened outgrowths of the epidermis).

I don't know if she has recently published on the subject, but papers and books by Jennifer A. Clack tell a lot on this subject.
Cheers to all
Jean-Michel

Here are some photos of Metoposaurus in situ material I photographed, have fun :)
http://allocrioceras.deviantart.com/art/Metoposaurus-skull-75553924
http://allocrioceras.deviantart.com/art/Metoposaurus-skulls-75554024

Clack hasn't published much on temnospondyls...

Anyway, I wrote:

To answer my own question: "The skull roof has a densely pitted surface and lacks any traces of lateral line sulci" in Edops craigi (ref p. 321). That ought to mean that the skin was directly attached to the skull like in crocodiles, probably leaving no space for a lateral-line organ. "Its occurrence and distribution" (same page) suggest a "semiterrestrial" way of life, too.

Rainer R. Schoch (2002/12/15): The evolution of metamorphosis in temnospondyls, Lethaia 35:309327.

And that's all wrong.

Although it has long been known that the sensory canals were subdermal (enclosed) among Devonian tetrapods, where their course is usually revealed by pores opening to the external surface, enclosed sensory canals may be more common among early tetrapods than is commonly believed, and these may not in all cases connect to the external surface by way of a marked series of pores. It was demonstrated above that at least a quadratojugal sensory canal was present and enclosed in Eryops, Edops, and Ossinodus, and it is likely that the entire sensory system was enclosed in cochleosaurids which have been considered to lack sensory sulci. In support of this hypothesis there is evidence of a [sic] enclosed sensory canal system on the quadratojugal in Chenoprosopus (Langston, 1953), while in Nigerpeton (Steyer et al., 2006) several sulci are visible where the external surface of the skull has eroded away (Milner, pers. comm., 2006). In these taxa there are no large external pores marking the course of the canals, as is also the case for the quadratojugal canal in Ossinodus, Edops and Eryops. The sensory canal system is likely to have been present but enclosed in parts of the baphetid skull; it is marked by open canals in the preorbital region but only appears more posteriorly on the inner surface of the quadratojugal (above). Hence, among early tetrapods, external absence of a line of pores does not necessarily mean that a particular sensory canal is absent. The absence of a system of sensory canals or pores on the outer surface of the skull in particular early tetrapods has been taken to be an indication that these taxa lack this sensory system that is associated with aquatic sensory perception, and that such tetrapods are more terrestrial than those in which the sensory canal system is expressed. The morphology found in Ossinodus suggests that 'the absence of evidence is not necessarily evidence of absence.'

From p. 860 of

Anne Warren (2007/12/12): New data on Ossinodus pueri, a stem tetrapod from the Early Carboniferous of Australia, JVP 27(4):850862.

It gets better. Dendrerpeton looks as terrestrial as Eryops, has never been considered aquatic, and also lacks visible lateral-line canals... in the skull. The ventralmost row of dorsal scales, on the other hand, contains the postcranial lateral-line canal. This is shared with the perennibranchiate Gerrothorax and has (in theory) been known since the original description by Dawson in 1882. I had no idea till today, when I read the chapter on temnospondyl phylogeny in Pawley's thesis.

These are seriously weird animals.

Hello! I am an portuguese student doing a study of an pre-historic animal, the Mastodosaurus.Could you force some information about him?
Thank you,
Cristiana Carvalho
cristiana_macieira@hotmal.com

Hi, i'm from South America, and my english is not "that good".
I have this "little" question : In the end, the temnospondyls are or not amphibians?

Thanks.

In the end, the temnospondyls are or not amphibians?

There is no consensus on that, because some think that the lissamphibians (frogs, salamanders, caecilians) are temnospondyls (in this case the temnospondyls are amphibians), while others think that the lissamphibians are lepospondyls (in this case the temnospondyls are not amphibians).

I'm working on this problem, as are several other people