Tetrapod Zoology

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The last few weeks have been pretty exciting for people interested in theropod dinosaurs…. but then, you could say this about most weeks: new theropods are constantly being published.

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Last week saw the publication of the weird, functionally two-fingered, short-footed maniraptoran Balaur bondoc from the latest Cretaceous of the Haţeg Basin in Romania (Csiki et al. 2010) [left foot of Balaur shown here, from BBC News]. When Balaur was alive, the Hateg region was an island, so this was another of those weird, island-dwelling dinosaurs we’ve often hoped would exist. I have a vested personal interest, given that its discovery has implications for work I’ve published on Haţeg maniraptorans (Naish & Dyke 2004).

Seeing publication today (in Nature) is the remarkable new Spanish carcharodontosaurian allosauroid Concavenator corcovatus Ortega et al., 2010 from the Barremian Calizas de La Huérguina Formation of Las Hoyas [life restoration above by R. Martín]. The Calizas de La Huérguina Formation is well known as a rich Lagerstätte (a place where fossils are exquisitely preserved, often including soft tissues traces). It has yielded several early bird fossils, the multi-toothed ostrich dinosaur Pelecanimimus, and many other neat fossils.

Concavenator is represented by a near-complete, articulated skeleton (about 6 m long) and is in excellent shape. As usual with new dinosaurs, it’s already much-discussed all over the blogosphere (Ed Yong’s take at NERS here).

Two things in particular make this animal really interesting.

Allosauroids with proto-feathered arms?

ResearchBlogging.org

The big deal about Concavenator – the one thing that probably near-guaranteed its publication in Nature – is that it preserves a row of small bumps on its ulna that look very similar to the ulnar papillae (or quill knobs) present on bird ulnae [see image below, borrowed from NERS]. In birds, these bumps anchor the ‘roots’ of the remiges, the large, vaned feathers that form the main surface of the wing. We’ve already known for a while that these structures aren’t unique to birds, as they’re present in at least some dromaeosaurs (Turner et al. 2007).

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The structures in Concavenator are well-defined and arranged in a definite line, and Ortega et al. (2010) conclude that these are most likely homologous with quill knobs: rather than possessing true feathers, the epidermal structures that grew from these knobs in Concavenator may have been short, stiff filaments. Could this mean that feather homologues first evolved in the neotetanuran common ancestor (the theropod that gave rise to both coelurosaurs and allosauroids), or is this more evidence indicating that quill-like structures were present throughout Dinosauria? As you’ll know, the possibility that the integumentary structures of theropods are homologous with the quills of some ornithischians, and even with the pycnofibers of pterosaurs, has been mentioned several times.

However, I admit to being slightly sceptical. Firstly, the bumps of Concavenator are way up on the lateral side of the ulna, not down close to (or on) the bone’s posterior border as they are in birds (and dromaeosaurs). Secondly, the bumps in Concavenator seem to be irregularly spaced, whereas true quill knobs tend to be spaced quite evenly. Ok, a ‘prototype’ stage may well have existed at some point, so differences like this are certainly not ‘killer’ points.

Thirdly, animals sometimes have weird, irregularly spaced tubercles arranged in lines on various of their bones, typically located on intermuscular lines (they presumably represent partially ossified attachment sites for tendinous sheets or similar structures): I’ve seen them on mammal bones and on a theropod tibia (specimen MIWG.5137, illustrated in Text-Fig. 9.29 of Naish et al. (2001)). In view of the differences apparent between the structures of Concavenator and true quill knobs, and the fact that a plausible alternative explanation exists, I hope you understand my scepticism. You may well argue that interpretation of these structures as prototype versions of quill knobs is more parsimonious. Maybe it is.

Poor, neglected Becklespinax

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The second really interesting thing about Concavenator concerns the neural spines on its dorsal vertebrae. Naturally, we tend to find things particularly interesting when they overlap with our own special interests. One of the dinosaurs I worked on for my PhD was Becklespinax altispinax, a mid-sized theropod from the Hastings Group rocks of East Sussex, southern England. It’s always been a bit of an enigma, and I discussed it at reasonable length in this Tet Zoo article from 2007 [Becklespinax holotype shown here, as illustrated by Richard Owen in the 1850s]. I’ve suggested that Becklespinax might be an allosauroid; if it is close to (or even congeneric with) Concavenator (read on), this identification would be correct, but it would also mean that, within Allosauroidea, Becklespinax is a carcharodontosaur, not a sinraptorid as I’ve proposed.

Of the three articulated Becklespinax vertebrae, the two more posterior ones (which I identified as the 10th and 11th vertebrae) have taller spines than the first. And note that these are posterior dorsal vertebrae (Naish 2006, Naish & Martill 2007), not anterior dorsals as has been generally assumed.

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In my 2006 thesis, and in a paper that reported some of the results of this work (Naish & Martill 2007), I suggested that Becklespinax might have looked really stupid: that it might have had a tall ‘sail’ restricted only to the posterior part of the back and sacral region. My reconstruction (which was included in Naish & Martill (2007), and was used online in the 2007 Tet Zoo article) shows this possibility [it's B in the adjacent image]. An alternative idea is that Becklespinax had a continuous sail, in which case the short first neural spine must represent breakage [A, in adjacent image].

What interests me in particular about Concavenator it that it essentially vindicates my stupid suggestion: in this theropod, the 11th and 12th dorsal vertebrae have really tall neural spines, five times taller than the centra. The spine of the 10th vertebra is shorter, but it’s still taller than the preceding 9 dorsals. While I assumed – I would say quite reasonably – that Becklespinax had tall sacral neural spines, Concavenator has really short ones that don’t even make it over the dorsal edge of the ilium. So, Concavenator had a short, tall sail (or hump) that rose abruptly from the posterior part of the back, and was restricted to this part of the back alone. As is obvious from Raul Martín’s excellent life restoration [used at very top], it would have made the animal look like it had a dorsal fin [image below - from NERS - shows Ortega and colleagues working on the spectacular Concavenator holotype].

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While I identified the tall-spined vertebrae of Becklespinax as vertebrae 10 and 11, I could easily be off by a position or two, so identification of the three Becklespinax vertebrae as vertebrae 10-12 works fine too. We don’t know anything about the sacral vertebrae of Becklespinax, but it’s obviously like Concavenator in having tall neural spines on those posterior dorsal vertebrae, and in having a neural spine preceding the two tall ones that was also tall, but not as tall. Ortega et al. (2010) noted that Concavenator is unique in having elongate neural spines on just two of its dorsal vertebrae, but they didn’t discuss the possibility that Becklespinax might have a similar condition, nor did they acknowledge my reconstruction where Becklespinax was given a short, tall sail in the posterior dorsal region (Naish & Martill 2007). This should have been mentioned and cited in their paper, but I can live with it. This sort of thing has happened before.

Becklespinax and Concavenator are further alike in lacking pneumatic fossae on the centra of their dorsal vertebrae, and they seem to be similar in size, too (the centra of Becklespinax are between 75 and 84 mm long, and the tallest neural spine is 350 mm tall; judging by the scale bars, the measurements are about the same in Concavenator). They’re also fairly close stratigraphically and geographically; indeed, the possibility that the Calizas de La Huérguina Formation and Wealden Supergroup might share certain faunal elements has been suggested on a number of occasions.

Given that Concavenator and Becklespinax are so similar, we have to wonder if they’re the same animal. Given that Becklespinax is only represented by three dorsal vertebrae (some other material was mentioned during the 1850s, but it seems to be lost), it’s not possible to be absolutely confident about this, even if they are identical in the anatomy of their posterior dorsal vertebrae (and note that the configuration of neural arch laminae and fossae – well known in Becklespinax because these areas are totally exposed (Naish 2006, in press) – isn’t yet clear for Concavenator).

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I would say that circumstantial evidence counts against them being the same species: Becklespinax is (most likely) from the Valanginian, whereas Concavenator is from the Barremian, and is hence about 10 million years younger [the stratigraphy of the Wealden Supergroup, shown above, should help give you some perspective on where the Valanginian and Barremian are with respect to each other]. Dinosaur species don’t, as a rule, seem to have lasted for more than a couple of million years. Genera, on the other hand, do seem to have durations of 10 million years (or more) in cases*, so it does remain plausible that Concavenator is, after all, a species of Becklespinax. They may differ in that the neural spine apices of Becklespinax are transversely thick and robust (this is, in fact, one of its potentially diagnostic features), but I can’t tell from the paper whether Concavenator exhibits this condition too.

* Remember, of course, that the boundaries of genera are essentially arbitrary and artificial.

All in all, Concavenator is a remarkable fossil, and I’m not in any way downplaying its importance or quality. Congratulations to Francisco Ortega and colleagues on this fabulous discovery, and in publishing a paper that brings it to global attention.

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I have one more thing to say: what were the tall neural spines for? Ortega et al. (2010) conclude that we just can’t say, though they note that thermoregulatory, display or energy storage functions have all been suggested. I tend to prefer the display option, but only by analogy with the extant tall-spined reptiles that everyone seems to ignore whenever they talk about tall neural spines. Sure, maybe these structures were partially buried in fat or muscle, but the implication from some that they simply must have been like this, and that the existence of ‘dorsal sails’ is a total no-no (Bailey 1997) ignores the fact that all tetrapods aren’t mammals. There are living reptiles with dorsal sails: I really must get photos of sail-backed chameleon neural spines some time [adjacent photo shows body of Meller's chameleon Chamaeleo melleri - best I can do at short notice. Photo by Adrian Pingstone, from wikipedia].

Ironically, I was going to talk about another paper on Cretaceous fossils that was also published today, but it’ll have to wait. And a particularly significant book was also published today. More on that later, too.

For previous articles on allosauroids and other Mesozoic theropods, see…

Refs – -

Bailey, J. B. 1997. Neural spine elongation in dinosaurs: sailbacks or buffalo-backs? Journal of Paleontology 71, 1124-1146.

Csiki, Z., Vremir, M., Brusatte, S. L. & Norell, M. A. 2010. An aberrant island-dwelling theropod dinosaur from the Late Cretaceous of Romania. Proceedings of the National Academy of Sciences 107, 15357-15361.

Naish, D. 2006. The osteology and affinities of Eotyrannus lengi and other Lower Cretaceous theropod dinosaurs from England. Unpublished Ph.D. Thesis, University of Portsmouth.

- . & Dyke, G. J. 2004. Heptasteornis was no ornithomimid, troodontid, dromaeosaurid or owl: the first alvarezsaurid (Dinosauria: Theropoda) from Europe. Neues Jahrbuch für Geologie und Paläontologie, Monatshefte 2004, 385-401.

- ., Hutt, S. & Martill, D. M. 2001. Saurischian dinosaurs 2: Theropods. In Martill, D. M. & Naish, D. (eds) Dinosaurs of the Isle of Wight. The Palaeontological Association (London), pp. 242-309.

Naish, D., & Martill, D. (2007). Dinosaurs of Great Britain and the role of the Geological Society of London in their discovery: basal Dinosauria and Saurischia Journal of the Geological Society, 164 (3), 493-510 DOI: 10.1144/0016-76492006-032

- . In press. Pneumaticity, the early years: Wealden Supergroup dinosaurs and
the hypothesis of saurischian pneumaticity. In Moody, R. T. J., Buffetaut, E., Naish, D. & Martill, D. M. (eds) Dinosaurs and Other Extinct Saurians: A Historical Perspective. Geological Society, London, Special Publications 343, 227-234.

Ortega, F., Escaso, F. & Sanz, J. L. 2010. A bizarre, humped Carcharodontosauria (Theropoda) from the Lower Cretaceous of Spain. Nature 467, 203-206.

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

Comments

  1. #1 John Harshman
    September 9, 2010

    Finally, back to archosaurs. Yay! Two pointless comments:

    1. How very prophetic is the name carcharodontosaurian? Cue Jaws theme.

    2. Just last week I found a cheap copy of Dinosauria II, having made do with Dinosauria I for years. And now it seems that Dinosauria III is desperately needed. Stop finding new fossils, dammit.

  2. #2 Jura
    September 9, 2010

    Thank you! While our ultimate views on where feathers finally wind up originating in dinosaurs likely differs, it’s nice to see someone else at least try to look for other possible explanations for these bumps. I was disappointed to read how readily the authors seemed to accept these structures as quill knobs in the paper. The authors never really addressed possible alternatives, and just stated that they “interpret the bumps to be quill knobs” and therefore (somehow) homologous with bird feathers etc. Much of the deliberation seemed to focus on the tall presacral spines instead. I don’t know, maybe this had something to do with space limitations in Nature (though there was no further mention in the supplementary material either).

    It’s also nice to see someone else point to the fact that we have extant sail-backed animals today, and that maybe we should look at what they do with their sails, if we would like to get an idea of what possible sail-backed dinosaurs did (hint, thermoregulation appears to be a secondary function at best for extant sail-backed taxa). I think I might have a picture of a Basiliscus skeleton around here somewhere. If I find it I’ll try to post it for easy access.

  3. #3 Andreas Johansson
    September 9, 2010

    Sure, maybe these structures were partially buried in fat or muscle, but the implication from some that they simply must have been like this, and that the existence of ‘dorsal sails’ is a total no-no (Bailey 1997) ignores the fact that all tetrapods aren’t mammals.

    I’m trying to imagine Dimetrodon with the spines buried in fat and muscle. Stupd-looking doesn’t begin to cover it.

  4. #4 David Marjanović
    September 9, 2010

    a rich Lagerstätten

    1 Lagerstätte, 2 Lagerstätten.

    If you’re picky, there are 12 regular ways to form the plural in German. (The irregular ways are reserved for loanwords.)

    I’m trying to imagine Dimetrodon with the spines buried in fat and muscle. Stupd-looking doesn’t begin to cover it.

    Also, the spines would just snap if those muscles did anything.

  5. #5 Angela
    September 9, 2010

    “One of the dinosaurs I worked on for my PhD was Becklespinax altispinax” … “and I discussed it at reasonable length”. Two phrases that when used together cause alarm bells to ring. :)

    (Though I did follow the link and the article was within the range of variation for Tet Zoo posts.)

  6. #6 Actuality Science
    September 9, 2010

    I’d read about the Balaur fossil earlier this week, but another cool dinosaur is such a short amount of time! Awesome!

    Interesting comments about the “quill attachment” nubs found on the forearm, I hadn’t really thought to question whether the nubs were early feather attachments or not, but you brought up some good points as to why we should question it. Hopefully next week they’ll publish another dinosaur that gives some more insight into the topic!

  7. #7 Mike Walley
    September 9, 2010

    I have a copy of your book Dinosaurs Life Size on my desk. It is a well-written and beautifully illustrated book, just a quick point on the dinosaur timeline (page 9), Herrerasaurus is not spelt correctly. Now back to Concavenator corcovatus, I share some of your scepticism. If this member of the Allosauroidea is evidence of feathered Theropods which are not akin to the Coelurosauria clade, could this just be an example of convergent evolution as opposed to concluding that more basal Theropods, ancestral to Allosauroidea and Coelurosauria must have been feathered.

  8. #9 Sordes
    September 9, 2010

    What I really don´t understand is that in the sail-issue very often completely different things are compared. Nearly everytime when it comes for example to the hypothetical function of the elongated spines of Spinosaurus, Dimetrodon is given as comparison. But the dorsal spines of this two animals are completely different, the only similarity is that both are elongated. Sadly I had no possibility to look at casts of Spinosaurus skeletons, but I looked at casts of Dimetrodon skeletons. Because I am interested in this special topic since several years, I always look at museums for all types of animals with elongated dorsal spines. Sadly I could nowhere find any skeleton of a modern reptile with really long dorsal spines, but at least some very good taxidermy specimens, which show the structure also very well, for example Hydrosaurus amboinensis or some of the Basiliscus species. Now if you look at them, the structure of the dorsal spines is remarkably similar to Dimetrodon, they are very long, thin and circular in cross-section, and really only covered with skin, quite contrary to the dorsal spines of Spinosaurus, Ouranosaurus or other animals with strong and laterally compressed dorsal spines. I am not saying that there was at any case some kind of hump, but probably at least in some cases, for example in Ouranosaurus. There is also another problem when we look again at Dimetrodon, because there was not only the typical Dimetrodon with which we are all familiar since our first contacts with prehistoric animals, but also a lot of other species, which differ sometimes remarkably in the shape of the dorsal spines, yet with a very conservative bauplan of the rest of the body. Hmmm. So why had some Dimetrodon-types fragile dorsal spines which are round at cross-section, whereas other ones had laterally compressed dorsal spines, which look far more robust? Why had an animal which was obviously(?)more in the macropredatory-nice such a fragile sail at all?

  9. #10 Zach Miller
    September 9, 2010

    Great rundown, Darren. I assume that if Concavenator turns out to be the same genus as Becklespinax, the latter would have priority?

  10. #11 AnJaCo
    September 9, 2010

    If the mating habits of large theropods were at all like those of birds and reptiles generally (i.e. male on top), then the ‘lumbar hump’ might have been an impediment to mating, suggesting that the specimen may be a male. Of course if such large beasts adopted a side-by-side mating posture then, well, never mind.

    The hump could have been an indicator of age/maturity and possibly gender at distance. Either or both would be useful bits of information for conspecifics.

    An ontogenetic series would be interesting and informative of course, as with all extinct critters [er, organisms, can't ignore the plants etc.]. So when are the next twenty random individuals of Concavenator going to be described? :-)

  11. #12 Nathan Myers
    September 9, 2010

    Am I alone in hoping this clumsy “Concavenator” name falls by the wayside, in favor of the appalling but bold Becklespinax?

    If, in fact, these things did have feather-like structures, is there any reason why the dorsal structure couldn’t be interpreted as support for a dorsal feather display? The same might be suggested for most flimsy dorsal extrusions we find on theropods.

  12. #13 gray Stanback
    September 9, 2010

    Something tells me that, 25 years from now, this is going to be one of those “stock dinosaurs” that you see in books for little kids, just because it looks so weird.

  13. #14 Augusto Haro
    September 9, 2010

    Great post Darren! You may be right in that the line of knobs can correspond to an intermuscular line, and this can be tested looking for the presence of a homologous intermuscular line between specific muscles inserted there on the extant archosaurs bracketing Concavenator.
    With respect to the difference in position, the knob line in your comparative figure seems to be aligned with the lateral corner of the distal articular surface in both specimens. May this suggest homology?
    Well, not necessarily, because Concavenator is most closely related to animals without the knobs than with those with them, so at present it may be most parsimonious to see the acquisition of the knob lines in Concavenator and among maniraptorans as convergences.

  14. #15 Steve P
    September 9, 2010

    “In my 2006 thesis, and in a paper that reported some of the results of this work (Naish & Martill 2007), I suggested that Becklespinax might have looked really stupid: that it might have had a tall ‘sail’ restricted only to the posterior part of the back and sacral region.”

    I recall seeing an image of “Altispinax” that looked very much like your reconstruction in A New Look at the Dinosaurs by Alan Charig – had this idea been postulated before your thesis was written?

  15. #16 John Scanlon FCD
    September 9, 2010

    AnJaCo:

    the ‘lumbar hump’ might have been an impediment to mating, suggesting that the specimen may be a male. Of course if such large beasts adopted a side-by-side mating posture then, well, never mind.

    In a lateral approach, it seems possible and might have been advantageous for the male to grasp the female’s lumbar eminence with the manus. Dinosaur love handles.

  16. #17 Eric
    September 9, 2010

    As cool as the sail is I think that the quil nobs probably have greater implications.

    After all not only are allosaurids now added to the list of the feathered dinos. But since Concavenator has scales as well as the quil nobs then perhaps it is time to rethink the whole scales equals non-proto-feathered.

    Okay so maybe it’ll just turn out that proto feathers can’t be located on any place but the arms, but Concavenator is still pretty cool!

  17. #18 William Miller
    September 9, 2010

    “I’m trying to imagine Dimetrodon with the spines buried in fat and muscle. Stupd-looking doesn’t begin to cover it.”

    Seems like it would have been quite top heavy and unstable, too, if the sail had any significant weight.

  18. #19 Boesse
    September 10, 2010

    >the ‘lumbar hump’ might have been an impediment to mating, >suggesting that the specimen may be a male. Of course if >such large beasts adopted a side-by-side mating posture >then, well, never mind.

    Think about porcupines. They have waaay more to prick their pricks with (so to speak) than Concavenator. Besides… with a laterally thin sail or ‘fin’, the male’s thorax could go on either side, which would be a prerequisite in the first place, since it would obviously have to go on one side or the other. Hmm… reminds me of that massive paper that came out on dinosaur sex.

  19. #20 AnJaCo
    September 10, 2010

    John Scanlon:

    it seems possible and might have been advantageous for the male to grasp the female’s lumbar eminence with the manus.

    Sounds very awkward. And how would such an odd behaviour originate/evolve? Also, I am thoroughly unconvinced that any theropod used their manus for grasping anything. But that’s another argument.

    Boesse:

    the male’s thorax could go on either side

    Not impossible. But still a bit restrictive perhaps.

    With such large animals the males probably had to have both feet firmly on the ground, unlike most [all?] birds who tread on the back of the female while [often] holding the nape of the female in the mouth. This gives them a kind of ‘three point stance’ for stability. Using the hyper-flexible tail [an under-appreciated character of birds and their close relatives IMHO] a moment of cloacal apposition is all that most birds need [I remember that those crazy ducks have their own style]. Non-avian theropods didn’t have this luxury and probably had to have an intromittent organ of some sort. So if a theropod employed a bird-like mating posture of treading on the back, then the ‘lumbar hump’ might be straddled, but this would require the hyper-flexible tail, which they don’t have, so assuming a male-on-top posture, the male’s belly would probably have to rest directly on the back of the female to some extent. The hump would be in the way. Could a male just slip to the side a bit? Perhaps. But given that strong control of the female by the male is the general rule in the mating of reptiles and birds, and slipping to the side might diminish this, my suspicion is that they wouldn’t/didn’t. My 2¢. Thanks for reading.

  20. #21 Darren Naish
    September 10, 2010

    Thanks for comments. So far, it seems like most people in the research community are also thinking that those quill knobs might not, after all, be quill knobs, and are also thinking that a close relationship (and possible congeneric status) between Becklespinax and Concavenator is likely. The generic name Becklespinax was published in 1991, so (Zach: comment 10) obviously has priority.

    Steve P (comment 15): artist Peter Snowball did indeed depict Becklespinax (labelled Altispinax) with a short, tall sail, but he showed it on the animal’s shoulder region. This was because the three vertebrae were assumed to be anterior dorsals (an error that started with Owen in 1855 and influenced the look of the Crystal Palace megalosaur). Some of this is covered in the 2007 Becklespinax article here.

  21. #22 Stu of the Peak
    September 10, 2010

    Interesting that at least two possible sail-backed theropods are now known from the Barremian of Europe; add to that the unique vertebra found by Steve Hutt (Hutt and Newbery, 2004) on the IOW which he assigns to D12, D13 or D14 of a baryonychid and you’ve got a hat-trick of high-spined carnivores, although the IOW animal sported a much lower sail than Becklespinax or Concavenator.

    Stephen Hutt and Penny Newbery; 2004. An Exceptional Theropod Vertebra from the Wessex Formation (Lower Cretaceous) Isle of Wight, England. Proc Isle of Wight Nat. Hist. Archaeol. Soc 20; 61-75.

  22. #23 AnJaCo
    September 10, 2010

    …but then Concavenator probably dealt with the “problem” however Spinosaurus et al. did.

  23. #24 Eric
    September 10, 2010

    Heh looks like I kinda jumped to conclusion there :).

  24. #25 Zach Miller
    September 10, 2010

    Something I just noticed: the caudal neural spines have strange little thorns, fore and aft. What the heck were THOSE fore?

  25. #26 Jerzy
    September 10, 2010

    So how this differs from mammals like toxodon or bison, which have noticeable shoulder hump to lift the heavy head?

  26. #27 Steve P
    September 10, 2010

    Re #21: Cheers for the correction and the information, Darren – fascinating stuff as always!

  27. #28 Andreas Johansson
    September 11, 2010

    So how this differs from mammals like toxodon or bison, which have noticeable shoulder hump to lift the heavy head?

    By not being near the shoulders, for a start.

  28. #29 Andrea Cau
    September 11, 2010

    @25:
    Zach, these are accessory neural spurs, often present in several basal tetanuran caudal vertebrae. Probably, they’re partly ossified interspinous legaments.

  29. #30 Jerzy
    September 12, 2010

    Maybe Becklespinax / Concavenator were semi-aquatic like otters and propelled themselves by sideways motion of tail.

  30. #31 Gwen
    September 12, 2010

    I agree with Jura, it seems everyone is happily jumping on the “quill knobs yay!” bandwagon. It’s nice to see someone examining the other possibilities.

    Although it is interesting to see quill-knob-like structures, given that one paper that said that Allosaurus had maniraptor-like wrists.

  31. #32 eddie
    September 13, 2010

    The sail put me in mind of dimetrodon, but then I got ytoy your post on basilisks.

    http://scienceblogs.com/tetrapodzoology/2009/01/something_new_about_basilisks.php

    The one shown there has a great sail, plus it has back legs much longer than front.

  32. #33 farandfew
    September 13, 2010

    Looking at the reconstruction I just can’t shake the feeling that Fred Flintstone has just hit it on the pelvis with a hammer.

  33. #34 Matt
    September 13, 2010

    While everyone seems fascinated with the sail and the possible quill knobs, am I the only person to think those feet seem awfully tiny?(at least in the reconstruction)

  34. #35 Kris
    September 13, 2010

    [from Darren: sorry, delayed by spam-filter]

    Good stuff… And here’s a very good, and very thought provoking photograph (you’ll see what I mean when you view it) of a crested chameleon (Chamaeleo cristatus).

    http://www.arkive.org/media/3C/3C5F61D2-5EA8-472F-B28E-6BA000A40023/Presentation.Large/photo.jpg

    I searched everywhere for a skeleton shot so as to see what the spines looked like, but no luck.

    However, here’s a shot of the skeleton of a veiled chameleon (Chamaeleo calyptratus).

    http://bioweb.wku.edu/faculty/huskey/Veiled%20chameleon%20skeleton%20rostral2.jpg

    It too has laterally compressed/elongated neural spines. As indicated from the photograph linked below, this chameleon does not have a fleshy hump…. just a nice, broad, flat display surface (yes, I know of at least one chameleon species that uses its broad body to thermoregulate… lives in the high mountains (it snows there) of the African Rift Valley).

    http://wwwtsrca.tripod.com/sitebuildercontent/sitebuilderpictures/maleveiledsmallest.jpg

    So… as Darren mentioned, based just on analogy’s sake, I’m convinced Concavenator (and indeed other sailed and plated dinosaurs) were using their goofy and metabolically expensive structures for what said structures are usually evolved for…

    Kris

  35. #36 Paul W.
    September 14, 2010

    I don’t know how to quote but I agree with Matt (post #34). However, looking at the specimen its self, it does look to have tiny toes. I wonder if that has any locomotive implications? I can’t imagine them being able to get around in soft surfaces very well and it reminds me of something like what I have noticed in some Carnotaurus reconstructions.

  36. #37 Matt
    September 14, 2010

    The tiny feet really stood out in the 3D animation someone made which got some tv airtime. It looked to be either a direct copy of this reconstruction.
    The walk seemed quite unnatural.

  37. #38 Paul W.
    September 14, 2010

    The reconstruction is probably a slight exaggeration but it must have got around somehow. If anything, in the reconstruction, the right foot looks slightly better proportioned than the left one which looks too weak to carry it.

  38. #39 Matt
    September 14, 2010

    Just looking at the skeleton, the feet are quite obscured, so it’s difficult to tell where the small feet came from.
    Perhaps I need to go look at some related animals to see if there really is a scale disparity or if it’s all in my head.

  39. #40 Paul W.
    September 15, 2010

    There are breaks in the matrix but purely from the untrained eye (mine) it does look like it has stubbier toes (as opposed to ‘foot’) than the average Allosaur. Of course, it could be a preservation issue.

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