Tetrapod Zoology

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Congratulations are in order: well done Dave Hughes, David Marjanovi? and Allen Hazen in particular. No, the creature shown yesterday is not a squabrat from The Dark Crystal (if there is such a thing), Romer’s hellasaur, an old picture of a colugo, a proto-bat, proto-pterosaur, arboreal theropod, antiquated archaeopterygid, tree shrew, climbing duck-possum, arboreal gorgonopsian, proto-ropen, or one of Dougal Dixon’s arbrosaurs: it is, instead, the hypothetical stem-haematotherm depicted in Philippe Janvier’s 1984 article on the Haematothermia concept. It made an appearance both within the article (yesterday’s picture) and on the cover (the original is in lurid colour, but I only have a black and white photocopy: what you see here – and below – is a low-res scan). Janvier’s article is in Spanish and my limited efforts at translating leave me confused as to exactly what Janvier made of the concept: he described it as an exciting idea, but one that failed to take account of the vast amount of data supporting the conventional notion that birds are closer to crocodilians than to mammals (Janvier 1984)…

According to the haematotherm theory, birds and mammals are sister-taxa, united by their endothermy, fully divided heart, respiratory turbinates, and by nerve and vascular characters, as well as others. The best known proponent of this concept has been Brian Gardiner; he published a few reasonably lengthy papers on the subject in high-impact journals, the best known of which is Gardiner (1982). Unfortunately, Gardiner has since become best known for this above all else, whereas his writings on vertebrate phylogeny in general, Piltdown, and on Darwin’s correspondence should be better known. I met him a few years ago (2002 I think) when he acted as external examiner for Alberto Vasconcellos’ Phd thesis, and he was still very keen on the idea then, arguing that if I was happy with the ‘traditional’ version of amniote relationships then that was up to me (i.e., I was stupid). Gardiner didn’t start the whole haematotherm thing however: Søren Løvtrup published on the theory earlier (Løvtrup 1977) and later provided a supporting paper (Løvtrup 1985). Both Løvtrup and Gardiner cited and discussed old observations by John Ray (from 1693!) and Richard Owen (from 1866), both of whom supported the idea of a bird-mammal group that did not include other tetrapods. Owen (1866) actually named this group Haematothermia: Løvtrup and Gardiner seemed to have overlooked this, and consistently used the alternative spelling Haemothermia.

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As was later discussed by a whole string of authors (e.g., Gauthier et al. 1988a, b, Kemp 1988, Benton 1985, 1991), one can only conclude that birds and mammals share characters not seen in other tetrapods by ignoring and excluding a vast amount of contradictory data. Løvtrup and Gardiner both ignored fossils, relied predominantly on soft tissue characters, and included only a handful of characters (literally, three or four) that contradicted the favoured topology and supported the traditional one: neither author included or discussed the huge number of bony and soft tissue characters that unite crocodilians and birds, for example. Furthermore, nearly all of the haematotherm ‘synapomorphies’ could be shown to be more widely distributed than proposed, non-homologous, or just plain wrong (e.g., Benton 1985, pp. 103-106).

As I’m sure I’ve said before, I admit to being a huge fan of what are politely termed non-standard theories, and what are less politely termed as fringe nonsense. Alternative theories like the haematotherm concept can be a good thing, because they force workers to tighten up ‘traditional’ models and to marshal a more convincing supporting data set, but they can also cause people to waste a lot of time when they could be doing something more useful! Whatever, we will be looking at a few non-standard theories in the near future, stay tuned…

And on the subject of using time constructively, I need to go – I am now away for the Big Cats in Britain conference and will be back next week. Have fun in my absence: remember to keep an eye on SV-POW! and also on the continuing debacle that is aetogate.

Refs – -

Benton, M. J. 1985. Classification and phylogeny of the diapsid reptiles. Zoological Journal of the Linnean Society 84, 97-164.

- . 1991. Amniote phylogeny. In Schultze, H.-P. & Trueb, L. (eds) Origins of the Higher Groups of Tetrapods: Controversy and Consensus. Cornel University Press (Ithaca, London), pp. 317-330.

Gardiner, B. G. 1982. Tetrapod classification. Zoological Journal of the Linnean Society 74, 207-32.

Gauthier, J. A., Kluge, A. G. & Rowe, T. 1988a. Amniote phylogeny and the importance of fossils. Cladistics 4, 105-209.

- ., Kluge, A. G. & Rowe, T. 1988b. The early evolution of the Amniota. In Benton, M. J. (ed) The Phylogeny and Classification of the Tetrapods, Volume 1: Amphibians, Reptiles, Birds. Clarendon Press (Oxford), pp. 103-155

Janvier, P. 1984. El divorcio del ave y del cocodrilo. Mundo Cientifico 32, 14-16.

Kemp, T. S. 1988. Haemothermia or Archosauria? The interrelationships of mammals, birds, and crocodiles. Zoological Journal of the Linnean Society 92, 67-104.

Løvtrup, S. 1977. The Phylogeny of Vertebrata. John Wiley, London.

- . 1985. On the classification of the taxon Tetrapoda. Systematic Zoology 34, 463-470.

Owen, R. 1866. On the Anatomy of Vertebrates, Volume 2. Longmans Green and Co., London.

Comments

  1. #1 Sven DiMilo
    March 6, 2008

    Gardiner, B. G. 1982. Tetrapod classification.

    Ah, that’s the nutso article I was trying to remember when reading yesterday’s speculations on Haematothermia.
    It seems so blindingly obvious (to me) that the ridiculous energetic expense of endothermy could not help but select for a bunch of convergent morphology & physiology that I have trouble believing anyone could take the “phlogenetic implications” of such characters seriously.
    But that’s tetrapod zoology for ya!
    Thanks for yet another fascinating and edifying post.

  2. #2 craig york
    March 6, 2008

    I’d never heard of Haematothermia before reading the last
    couple of postings-considering the amount of time I spend
    on the ‘nutso fringe’ its a little surprising. I can see
    some of the less responsible Cryptozoologists seizing
    on the concept to explain any number of mystery beasts…
    Still, as a memeber of the great unwashed, I can only rely
    on the intelligence and insight of informed sources, and
    for that, and this blog, I thank you. Hope the Big Cat
    conference goes well.

  3. #3 Mike from Ottawa
    March 6, 2008

    goodbye from me

    I hate when you do that!

  4. #4 Zach Miller
    March 6, 2008

    Of course Haematothermia is real. And bats are intermediate between flying primates and birds. IT’S SO OBVIOUS!

  5. #5 Mike from Ottawa
    March 6, 2008

    remember to keep an eye on … the continuing debacle that is aetogate.

    I am following it, and you Mike, Matt and Jeff have done a very good job putting together materials and also shown commendable restraint in what you’ve claimed. You guys are the kind of folk a lawyer would like to have for clients. Ashman? Ennh, not-so-much.

  6. #6 Cameron
    March 6, 2008

    I don’t know Zach, my own studies say otherwise. Darren himself noted a startling, nay, suspicious, similarity between the tarsometatarsus of birds and the metatarsus of, that’s right, jerboas. CLEARLY jerboas represent the primitive condition for Haematothermia, and, uh, other mammals are just atavistic freaks. Also, I think the beady eyes and round bodies make jerboas look startlingly like small passerines.

  7. #7 neil
    March 7, 2008

    Ugh, I’m afraid I’ve unleashed a monster, er, hellasaur…but I’m glad the term is catching on with all the underemployed does and bucks. I just hope I don’t see “heckasaur” showing up in some state bulletin soon…

  8. #8 David Marjanovi?
    March 7, 2008

    I completely failed to notice… this is not an amniote at all. Look, it lacks any trace of eyelids. If it’s a tetrapod in the first place, it’s a neotenic salamander. A long-limbed long-necked heterodont tree-climbing hairy gillless axolotl!!!1!

    If it’s a salamander, that also explains why it has four fingers…

  9. #9 Andreas Johansson
    March 7, 2008

    Hairy gilless axolotl? Surely it’s more parsimonious to assume that the “hair” is, in fact, gills.

  10. #10 Pavel I. Volkov
    March 7, 2008

    Darren, I also want to pose a puzzle. In my site there is a page of “biological freaks”. Go here:
    http://www.sivatherium.h12.ru/biolap/lapsus.htm
    and just try to guess, what is an animal, which plastic figure is pictured at the first photo.

  11. #11 Allen Hazen
    March 8, 2008

    Pavel Volkov–
    Neat! And your site makes me wish I could read Russian.
    The black plastic figuring looks to me like a speculative (and– unfortunately, since it is so cute– not very plausible) reconstruction of Ambulocetus. (I say not very plausible because I don’t think there is evidence of flukes evolving at this early stage of Cetacean evolution.)

  12. #12 Pavel I. Volkov
    March 8, 2008

    Allen, it is not Ambulocetus. Just look at its muzzle.
    I think authors of that toy wanted to make a kind of fur seal. But its cetacean-like tail makes this one chimaeric creature.
    This page is dedicated to biological freaks, mainly in ignorant translation from English and German into Russian in popular literature. It’s a problem for education, I think. And you’ll not understand the reason of placing of some examples here. For example, the number of birds in Russian has the unique names, and in English their names look like “main name + specific epithet”. But the photo of gibbon, for example, illustrates the variability of South-American monkeys. And diamond pheasant from china is placed to the article about Issyk-Kul Lake in central Asia.
    The picture of half-cutted Basilosaurus will be soon.

  13. #13 neil
    March 8, 2008

    wow I was well off. Was a wild stab in he dark thou!

    An interesting theory about the bird and mammals being sister groups – even if it is complete nonsense :)

  14. #14 Allen Hazen
    March 8, 2008

    Pavel–
    Well, someone has posted a link to a picture of a Basilisk (also known as a Cockatrice) to the Dinosaur Mailing List, so a Chimaera is fine by me! (Smile.)
    I noticed the seal-like head, but since Ambulocetus is often compared to a Sea Lion, assumed that the model-maker had based an Am… reconstruction on an eared seal. But you’re right: an Ambulocetus ought to have a much longer snout.
    It’s cute, though!

  15. #15 Stevo Darkly
    March 9, 2008

    Mr. Volkov, I have two guesses about the identity of that plastic animal:

    1) It could be a depiction of a sea lion by someone who is only somewhat familiar with sea lions.

    2) It reminds me of a reconstruction of a prehistoric animal that I saw in a newsletter when I was in 8th grade, called Paleoparadoxia. It was portrayed as something like a seal with longer, but oddly splayed, legs, and a vaguely hippo-like head. At the time it was said to be a possible ancestor of whales.

    Nowadays I understand that Paleoparadoxia is classfied as a “desmostylan” and not considered a whale ancestor, and the reconstructions I see today are less seal-like and more hippo-like. Perhaps the plastic animal is based on an old reconstruction of Paleoparadoxia, and the tail is derived from the idea that it was a whale ancestor.

  16. #16 Pavel I. Volkov
    March 9, 2008

    It is not Paleoparadoxia at all. Bu size and constitution this one looks like cross between pig and hippo. I had seen the complete skeleton of this one in Paleontological Museum (Moscow). The main feature of this one is very short tail not resembling whale’s one.
    As for me, I think this animal was made as an image of sea lion. But, of course, whale tail of this one is the obvious mistake. I also think the maker of this tiny monster even does not know such paleontological wonder, as Paleoparadoxia.
    The sleep of mind gives rise to monsters in any time.

  17. #17 Dave Godfrey
    March 9, 2008

    Hmm. It could be an outdated Pakicetus. Virtually all the restorations I recall from before they found the postcrania reconstructed it as looking much more whale-like, sometimes giving it flukes.

  18. #18 Andreas Johansson
    March 9, 2008

    I’m willing to bet it’s supposed to be some kind of pinniped.

  19. #19 Rajita
    March 16, 2008

    I remember reading an article by Gardiner when i was kid. It appalled me so much that I did spend a while turning the whole thing over many time until I convinced myself it was nonsense. But it taught me that the wonders of convergence are wonderful. There was this paper of Simmons et al IIRC which created the mammalian clade Volitantia uniting bats and dermatopterans. Most “synapomorphies” were convergences ! This issue will continue to plague morphological phylogenetics especially given that we do not fully understand correlation between various characters caused by re-use of same or similar molecular pathways in different places.

    As for “aetogate” I do feel it is good to see the palaeontologists taking it seriously. On the whole it seems a more honest field than molecular biology or biochemistry where I know of multiple such infractions most of which are just passed by without even a protest.