Tetrapod Zoology

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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).

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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.

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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.

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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.

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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).

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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.

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.

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.

Comments

  1. #1 Lars
    June 29, 2007

    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...]

  2. #2 Zach Miller
    June 29, 2007

    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.

  3. #3 Sordes
    June 29, 2007

    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.

  4. #4 David Marjanovi?
    June 29, 2007

    *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, Vis�an, 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, Vis�an, 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).

  5. #5 Shamini
    June 29, 2007

    Oh if only you could have posted this before my finals – my attempted essay on temnospondyls suffered from a complete memory blank!

  6. #6 Mike
    June 30, 2007

    “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.

  7. #7 Allen Hazen
    June 30, 2007

    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.

  8. #8 Neil
    June 30, 2007

    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!

  9. #9 Randy
    July 1, 2007

    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.

  10. #10 David Marjanovi?
    July 1, 2007

    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.)

  11. #11 Darren Naish
    July 1, 2007

    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.

  12. #12 David Marjanovi?
    July 1, 2007

    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.)

  13. #13 David Marjanovi?
    July 2, 2007

    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 35:309–327.

  14. #14 R. A. W.
    October 31, 2007

    The article (here) says these temnospondyl impressions point towards naked skin?

    What say ye?

  15. #15 David Marjanovi?
    November 1, 2007

    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).

  16. #16 Jean-Michel BENOIT
    April 3, 2008

    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

  17. #17 Dawid Mazurek
    April 4, 2008
  18. #18 David Marjanovi?
    April 24, 2008

    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 35:309–327.

    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):850–862.

  19. #19 David Marjanovi?
    June 10, 2008

    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.

  20. #20 Cristiana Carvalho
    October 18, 2008

    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

  21. #21 Martín
    December 9, 2008

    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.

  22. #22 David Marjanovi?
    December 10, 2008

    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…