Tetrapod Zoology

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So I’ve done the pterosaur meeting; now you all know all about it. But what about the 55th Symposium on Vertebrate Palaeontology and Comparative Anatomy, held at the University of Glasgow between August 29th and September 1st, and described for some reason as ‘The best conference ever’, I hear you cry? After much deliberation I have decided to do a brief rundown of the tetrapod talks: and my intention is to be as brief as possible about talks and their contents, not to review them at length or properly summarise them. As usual, I regret that I’m only covering those talks that appealed to me personally; I can’t be bothered to review everything. If you want to know more about any of the talks I mention (as well as about those that I don’t), remember that the abstracts are available online at the SVPCA site here. Ok, here we go…

[in the adjacent images, Adam Smith and Peggy Vincent ponder the neck of the Hunterian Museum's Cryptoclidus (Dougal Dixon is at far left). In the lower image, Matt Williams poses with the Bath cast of Rhomaleosaurus cramptoni (from here)]

In some senses, this meeting had a fishy theme to it. You might expect this given that the organiser, Jeff Liston, recently completed his phd on the Jurassic pachycormid Leedsichthys, but not only did we have the usual run of talks on placoderms, chondrichthyans, sarcopterygians and actinopterygians, the field trip that ended the conference was at the relatively local, famous, fish-bearing sites of Bearsden and Lot’s Wife. Because I love falling down hillsides (thanks Neil), tumbling into streams, rooting around in the mud, and getting soaked to the skin by way of Scottish rain, I decided to go along. I found bugger all, save for a live pseudoscorpion and some fox shit. Oh yeah, and some chunk of fossil arthropod. I also cut my finger open thanks to a strategically positioned chunk of glass. The photo below shows what we looked like after the event (photo courtesy Emma-Louise Nicholls). I’m down at the front, my hand on Jon Jeffery’s inside leg (he’s reclining). Anyway, enough with the nostalgia.

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So on to the talks. Once fish were out of the way, Marcello Ruta looked at temnospondyl diversity across the Permo-Triassic boundary, and Alexandra Houssaye examined the issue of how reliable identifications of isolated squamate vertebrae are (quite a problem when several Cretaceous clades evolved similar long-bodied morphologies). My former office-mate Sarah Fielding spoke about her work on Jurassic testudines: a number of Jurassic testudine clades (including Platychelidae, Notoemydidae, Eurysternidae and Plesiochelyidae) are alleged to have been marine, but this is based on their shell shape (which is unreliable as a guide) and depositional environment (also unreliable). However, by looking at evidence for cranial salt glands, and by compiling ternary plots of limb proportions, it can be shown that these turtles were predominantly marine after all. Marc Jones gave a really good talk on cranial sutures in tuataras: one interesting snippet he mentioned is his discovery that Sphenodon punctatus and S. guntheri can be distinguished osteologically. The idea that these two species might be distinguishable was recently challenged by Worthy & Holdaway (2002).

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Most people interested, or involved, in zoology know that dinosaur research has undergone a renaissance within the past few decades, and pterosaur research arguably has too. Less well known is that a major new research cycle is now well underway in the field of plesiosaur research, and this is definitely reflected in the number of conference talks that are now devoted to this amazing group of animals. Hilary Ketchum covered her new work on plesiosaur phylogeny: her study appears pretty comprehensive and is based on personal examination of most relevant specimens. In agreement with O’Keefe (2001), she found polycotylids to be part of a mostly long-necked clade, and not close to pliosaurids. I want to say more about polycotylids and will do in the near future: consider that Edgarosaurus muddi Druckenmiller, 2002, Thililua longicollis Bardet et al., 2003, Manemergus anguirostris Buchy et al., 2005, Palmula quadratus Albright et al., 2007 and Eopolycotylus rankini Albright et al., 2007 have all been named since 2002, and you can see that the group is proving quite a fertile area of research [adjacent Dan Varner art of two fighting polycotylids borrowed from his paleo-art page at oceansofkansas.com].

Adam Stuart Smith reviewed his recent work on Rhomaleosaurus cramptoni, the type specimen of which (originally near-complete and articulated but later broken up into pieces with a sledgehammer) has now been prepared and cleaned at the NHM. R. cramptoni turns out to be rather different from other Rhomaleosaurus species, and all of this resulted in some generic reallocation (cough Eurycleidus cough). I won’t spoil the surprise (errr) – I’m sure Adam is due to publish soon. Adam also unveiled the very first full-body skeletal reconstruction of a rhomaleosaur. If you’re interested in his stuff check out his page at plesiosauria.com.

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Donald Henderson – best known for his work on what I suppose you might call mathematical palaeontology – broke with tradition and spoke about rocks and fossils: specifically, about the discovery and excavation of a new elasmosaurid specimen from the Bearpaw Formation of Alberta. In keeping with his Scottish ancestry, he gave the entire talk in a Scottish accent. Honestly, he did! Peggy Vincent discussed Plesiosaurus macrocephalus from the Lias of Lyme Regis (holotype shown in adjacent image: borrowed from plesiosauria.com). It is not referable to Plesiosaurus but appears to represent a new genus. Finally, Mark Evans gave a frighteningly well illustrated talk on the evolution of the plesiosaur braincase, covering homology, terminology and the distribution of such characters as the pterygoid flanges. A lot of phylogenetic information is clearly present in the plesiosaur braincase, and Mark implied that braincase characters might be less prone to homoplasy than characters that come from elsewhere in the skeleton, supposedly because the braincase is less affected by functional constraints than the other regions of the body. Other workers have stated the same when looking at the braincases of dinosaurs and other taxa (e.g., Currie 1996). However, there are some indications that this is not really true: Oliver Rauhut (whom I caught up with in Munich at the pterosaur conference) has found that braincase characters are just as prone to homoplasy as characters from any other part of the skeleton, so much so that Oli recently published a short paper titled ‘The myth of the conservative character: braincase characters in theropod phylogenies’ (Rauhut 2007: a longer version is in preparation).

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Moving now to archosaurs, there were some neat crocodyliform talks. Mark Young spoke about a new phylogenetic analysis of metriorhynchids (if you need to know what they are, check out the ver 1 article here). His work seems to show that Geosaurus, Metriorhynchus and Dakosaurus are all polyphyletic or paraphyletic, so to get taxonomy to match phylogeny we have to resurrect quite a few old names, including Enaliosuchus, Cricosaurus, Neustosaurus, Rhacheosaurus and Suchodus. More on this when his paper is published. Marco Brandalise de Andrade discussed the dentition of notosuchians and other Cretaceous Gondwanan crocodyliforms. Mariliasuchus, Sphagesaurus and others have tooth morphology, occlusion styles, and types of jaw movement that suggest that they were neither strict carnivores nor herbivores, but omnivorous generalists. In keeping with what I said in the sebecosuchian article a while back, remember that these crocs were contemporaneous with dinosaurs and that the Mesozoic wasn’t a dinosaur-only theme park [the adjacent photo depicts a scene from the auction, held in Glasgow University's zoology museum. Les Noč and Marc Jones preside; tuna and leatherback turtle fly overhead].

Only one talk was devoted to pterosaurs: this was Dave Unwin’s on the morphology and extent of the propatagium (for more on this see the article on the Wellnhofer conference here). Given that – as regular readers know full well – a week-long conference devoted entirely to pterosaurs was happening just a week after SVPCA, I think we can forgive people for not doing more pterosaur talks at the meeting.

And that’ll have to do for now: in the next part I’ll do the dinosaurs, mammals, and whatever else is left over. It’s my birthday tomorrow, so don’t expect any blog posting… I’m going out. Toni is in charge. This time.

Refs – –

Currie, P. J. 1996. Out of Africa: meat-eating dinosaurs that challenge Tyrannosaurus rex. Science 272, 971-972.

O’Keefe, F. R. 2001. A cladistic analysis and taxonomic revision of the Plesiosauria (Reptilia: Sauropterygia). Acta Zoologica Fennica 213, 1-63.

Rauhut, O. W. M. 2007. The myth of the conservative character: braincase characters in theropod phylogenies. Hallesches Jahrbuch Geowissenschaften B 2, 51-54.

Worthy, T. H. & Holdaway, T. H. 2002. The Lost World of the Moa. Indiana University Press, Bloomington, Indiana.

Comments

  1. #1 Nick Gardner
    September 25, 2007

    I’ll be the first to say I’m quite curious about these ornithischian presentations! :D

  2. #2 David Marjanovi?
    September 25, 2007

    Not having read or known about Rauhut’s paper, I suppose braincase characters are statistically unlikely to converge in the same animals in which the rest of the skeleton converges, because they are less subject to biomechanic constraints. However, this means that they are free to converge at random — so a braincase-only phylogeny is no more guaranteed to be accurate than a lower-jaw-only one, even though the two phylogenies have a rather high probability of being quite different. Take-home message: total-evidence approach.

    Right?

  3. #3 johannes
    September 25, 2007

    Is this really a melon on the heads of those fighting polycotylids (splendid palaeo art, btw)?

    And if it is indeed a melon – has this reconstruction a scientific foundation, or is it just artistic licence? In other words, do the fossils of plesiosaurs or other marine reptiles contain any traces of a structure similar or homologous to the melon of cetaceans?

  4. #4 Brad McFeeters
    September 25, 2007

    Does anyone have a .pdf of Rauhut 2007?

  5. #5 Anthony Docimo
    September 25, 2007

    Happy birthday!

    thank you for this long post, sharing all this information with us. great pictures too, btw; and it sounds like you had great fun at the conference.

    again, Happy Birthday.

    have fun, be well, and have nice days.

  6. #6 Dan Varner
    September 25, 2007

    This painting of mine that Darren has reproduced was a private commission meant for fun. Those are the ones that come back to haunt you. The “melon” is simply meant to be a muscle mass, although I had given thought to a cetacean melon, to be honest. The painting is roughly based on this taxon: Jim Martin of the South Dakota School of Mines and Tech has a nice specimen of a phalange of this animal impaled by a tooth of its own kind, hence the genesis of this painting. Now I’m off to the courthouse to renew my artistic license. Happy B-Day, Darren!

    [from Darren: many thanks Dan.. and I hope you're ok with me using the picture :) ]

  7. #7 DDeden
    September 25, 2007

    The lake baikal seal has huge eyes which has pushed back the other parts of the skull, (opposite of river dolphins with small eyes and big melon), I presume the same occurred in the ples. Hydrodynamic soft tissue perhaps. Is there any way to know if they had subcutaneous fat, especially those with dense bones, as seen in slow divers? Did any dinos have fat, or were they just skin, muscle and bone and guts?

  8. #8 Mike Dickison
    September 26, 2007

    Fascinated to hear about Marc Jones being able to distinguish the two species of tuatara osteologically. From my conversations with various tuatara people, they don’t seem to be good species; Sphenodon guntheri is distinguishable only by blood allozymes, not by DNA let alone morphology, and is more closely related to southern S. punctatus than these are to their northern conspecifics. S. guntheri is probably a island-bottlenecked tip of a southern cline, which makes Marc’s discovery surprising. What is puzzling is the possibility that New Zealand produced only a single species of Sphenodon despite 80 million years of isolation. When I looked at all the tuatara material in NZ collections for my Hons project I was noticing huge amounts of variation in the mainland subfossils, so there could well be some species to be described there.

    [from Darren: I'm really hoping I don't get Marc into trouble by talking about his discovery - there is more to it than what I said, but for that we'll have to be patient... ]

  9. #9 David Marjanovi?
    September 26, 2007

    Is there any way to know if they had subcutaneous fat

    I don’t think so. Fat neither fossilizes nor leaves any traces on bones that I’m aware of.

  10. #10 Michael P. Taylor
    September 26, 2007

    Johannes asked: “Is this really a melon on the heads of those fighting polycotylids?”

    No, they’re just pleased to see you.

  11. #11 johannes
    September 28, 2007

    I wish you a (belated) happy birthday, Darren!

    [from Darren: thank you!]

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