How did the centenary workshop on mammal bone identification go, I hear you cry? It went very well, thank you very much. Anyway, as promised here are more of various recollections from the 55th SVPCA, held at the University of Glasgow between August 29th and September 1st. For previous of my thoughts visit part I here, and for abstracts, photo galleries and more, visit the SVPCA site here. In this article, I’m going to review the dinosaur talks. You have been warned.
[I should explain the photo montage used here. For reasons that might have been mysterious to him, Bob Nicholls (of paleocreations.com – here photographed at the SVPCA whisky tasting evening) has often found himself compared to Hemicentetes semispinosus, the Lowland streaked tenrec. This montage shows, I hope, why. At bottom right I’ve thrown in one of Bob’s pictures: the alligatoroid Deinosuchus exacting revenge on an over-rated theropod cousin. Did Deinosuchus really look like that? Hmm… that would be telling… ]
So, dinosaurs. I don’t get the impression that the meeting was dominated by dinosaurs (as discussed in the part I article, marine reptiles were well represented, and there was a reasonable amount of stuff on mammals), but representation was good. Dave Hone reviewed his work on Cope’s Rule – the idea that species tend towards larger sizes within the history of lineages. Work on dinosaurs and pterosaurs suggests that Cope’s Rule was in action (Hone & Benton 2007, Hone et al. 2005). My main problem with the concept of Cope’s Rule is the implication that there is an inherent genetic tendency for organisms to increase in size. My feeling instead is that organisms increase in size when ecological or morphological factors allow it, but then… maybe this is the same thing as Cope’s Rule. Note also that many lineages thought to exhibit Cope’s Rule actually don’t – it just looks like they do because of biased sampling (horses are a good example: see Gould & MacFadden 2004). Feel free to correct my naive ramblings Dave.
Paul Barrett looked at dinosaur diversity across the Mesozoic. Diversity curves for ornithischians, sauropodomorphs and theropods (including birds) indicate that the specific and generic diversity of ornithischians and theropods is controlled by the number of dinosaur bearing formations in the geological record, but that sauropodomorph diversity does not correlate with expectations. There was an awful lot more to the talk than this, but my notes are rubbish. Nizar Ibrahim reviewed new work on the Kem-Kem beds of Morocco. Digging fossils here is dangerous work: the local people have constructed deep tunnels, and fatal accidents caused by cave-ins and collapses are not uncommon. Nizar discussed the fact that north African Upper Cretaceous dinosaur assemblages appear odd in that carnivorous taxa are particularly well represented. For more on this see Naish et al. (2004) [adjacent dinosaur panoply from here. I must find out who the artist was].
New work on dinosaur ichnology was presented by Neffra Matthews and Brent Breithaupt, and Richard Butler looked at how the distribution of Cretaceous herbivorous dinosaurs matches with palaeoenvironmental data. In general, Cretaceous herbivorous dinosaur fossils are positively associated with terrestrial environments, nodosaurids and hadrosaurs are more associated with marine depositional environments than other ornithischians (suggesting that they inhabited coastal plain environments), and ceratopsians and pachycephalosaurs exhibit strong associations with inland terrestrial environments.
Kent Stevens spoke about kinematic constraints and what they mean when it comes to reconstructing dinosaur gaits. Some gaits reconstructed for TV programmes have been largely intuitive and do not reflect the advice of technical experts: a gait reconstructed for Triceratops, for example, might be largely modelled on that of a rhino, but only because it ‘looks right’; not because it’s what the anatomy, or the consulted experts, suggest. Ranges of motion possible at joints, inertial properties, and estimates of metabolic cost can all be used nowadays to produce more accurate models of dinosaur gait. Kent showed some excellent new animations, including of a walking Diplodocus and a new-look Tyrannosaurus. I won’t spoil the one key surprise, as I’m sure Kent will be presenting the same animation at other conferences.
Sauropodomorphs were the focus of just one talk: Paul Upchurch’s on Euhelopus. Paul reviewed new work on the morphology and phylogenetic position of this taxon being undertaken by Paul and Jeff Wilson. New data and analysis confirms that Euhelopus is a somphospondylian titanosauriform: in other words, that the phylogenetic hypothesis of Wilson & Sereno (1998) was right. Erketu shares several derived characters with Euhelopus and seems to be a euhelopodid [the composite image above, borrowed from Kent Steven’s DinoMorph site, combines Wiman’s original reconstruction and figure of 1929 with Greg Paul’s rather more erect-necked version from recent years].
Moving now to theropods, one of the most memorable talks of the conference was given by Vincent Fernandez: it concerned the tiny dinosaur eggs discovered in Lower Cretaceous Thailand and published by Buffetaut et al. (2005). These eggs are about 18 mm long and contain the remains of tiny baby theropods [adjacent image of one of the eggs from here]: the eggshell microstructure is typical of non-avian saurischians, and it’s been suggested that the babies might be microraptorians or epidendrosaurs. By using X-ray propagation phase contrast microtomography (learn it, for use at dinner parties*), Vincent and colleagues were able to produce 3D scans of some of the embryos (which are, of course, very much embedded within the sediment that now fills the eggs). This technique allows an embryo to be depicted, three-dimensionally, in-situ, as if it were floating in space, rather than embedded within matrix. The image was rotated, and the individual bones could be digitally moved and repositioned. It’s still not clear what sort of theropod the embryos represent. The skulls had disarticulated, and the lower jaws appeared to be edentulous.
* My other favourites are resistant-fit theta rho analysis and matrix-assisted laser desorption ionisation mass spectrometry.
Roger Benson spoke about a new theropod taxon from the Kimmeridge Clay of Dorset: this is the interesting beast that has been sitting in the Oxford Museum of Natural History for some years now (Martill et al. 2006 discussed it briefly). I mentioned it in passing in a ver 1 article that some of you might remember from last year (go here). It turns out that this theropod is a new basal tyrannosauroid, and more specifically a new species of Stokesosaurus. A paper on this animal is due to appear soon, and given my vested interest in basal tyrannosauroids I will discuss it further in due time.
I gave one of my usual talks on poorly-known Lower Cretaceous taxa known only from scrappy remains: this time round it was Becklespinax and Valdoraptor. While it is well known that both taxa (known, respectively, from articulated dorsal vertebrae and a partial metatarsus) are from the Wealden Supergroup, less appreciated is that they come from the Berriasian-Valanginian Hastings Beds Group – a unit that is between 10 to 20 million years older than the Barremian Wessex Formation of the Isle of Wight (the Wealden unit that has yielded virtually all of the well-known Wealden dinosaurs). Some of this stuff was covered in the British dinosaurs paper that Dave Martill and I published earlier this year (Naish & Martill 2007), but for the full, detailed discussion you’ll have to wait for the paper, as they say. Or maybe you won’t: I’m publishing an edited version of my talk here on the blog, probably next.
Wealden theropods were also looked at by Steve Brusatte who, together with Steve Hutt and Roger Benson, has been working on the Neovenator monograph. Neovenator is well supported as a basal carcharodontosaurid and shares a number of characters (some previously noted, some not) with other members of this clade. Within Carcharodontosauridae, we can now say that the giant size and highly apomorphic skulls of the South American and African taxa evolved after the axial and hindlimb characters that characterize the clade [adjacent image shows Neovenator skull as previously displayed at the old Museum of Isle of Wight Geology, Sandown].
Birds formed the focus of just one talk: Stig Walsh’s on the evolution and distribution of the wulst and of other brain characters. The increase in the size of the neornithine brain may have been correlated with sensory integration and cognition, and not with flight adaptation, and increased encephalisation and wulst size in neornithines may have made them more behaviourally flexible than other avian clades. This might explain why neornithines, alone among birds, were able to survive beyond the end of the Cretaceous.
A couple of talks – literally – were devoted to ornithischians. Tom Hübner looked at the palaeobiology of Dryosaurus lettowvorbecki. Animals in the Tendaguru bonebed range in size from 75 cm to perhaps 5 m, and postcranial morphology is similar across size classes. Bone microstructure indicates fast avian-style growth. Some of these conclusions totally contradict previous assertions about dryosaurid palaeobiology (Heinrich et al. 1993): I look forward to seeing this data published.
Eric Buffetaut reviewed the current status of Psittacosaurus sattayaraki, and argued again that it is indeed referable to Psittacosaurus, contrary to arguments stating otherwise. As all dinosaur aficionados know, the number of named Psittacosaurus is pretty staggering… well, actually, it’s not in the least bit staggering when we remember that species referred to this genus span perhaps 40 million years. But for a Mesozoic dinosaur genus (the vast majority of which are monotaxic), Psittacosaurus is unusually speciose: there are as many as 14 valid species, three of which have been named since 2000. They are: P. mongoliensis Osborn, 1923, P. osborni Young, 1931, P. sinensis Young, 1958, P. youngi Chao, 1962, P. guyangensis Cheng, 1983, P. meileyingensis Sereno et al., 1988, P. xinjiangensis Sereno & Chao, 1988, P. sattayaraki Buffetaut & Suteethorn, 1992, P. ordosensis Russell & Zhao, 1996, P. neimongoliensis Russell & Zhao, 1996, P. mazongshanensis Xu, 1997, P. lujiatunensis Zhou et al., 2006, P. sibiricus Averianov et al., 2006 and P. major Sereno et al., 2007. Not all of these species are accepted as valid by all workers of course: which are valid depends on who you ask. Thanks to the fact that literally hundreds of specimens are known, and that we have exceptional fossils (like groups of babies preserved in association, sometimes associated with an adult), a lot more is known about the palaeobiology of psittacosaurs than that of most other Mesozoic dinosaurs. To cover this I’d need to devote an article to the subject – maybe one day I will [adjacent art, depicting various psittacosaur species, is by Arthur Weasley and is available here at wikipedia’s Psittacosaurus entry].
Anyway, there endeth the reptile stuff. I don’t have time to properly write-up all the mammal stuff I’m afraid: among much else, Felix Marx looked at the confusing story of tooth replacement in Morganucodon, Jerry Hooker looked at European Eocene plesiadapiforms, and Eleanor Weston looked at brain size in dwarf Madagascan hippos. As Eleanor explained, while there has been an awful lot of debate over brain size and dwarfism in hominids, data from other insular dwarf mammals has been suspiciously absent. Due to a lunchtime meeting that concerned a possible post-doc project, I missed Steve Wroe’s talk on the mechanical behaviour of dingo and thylacine mandibles. A paper on this has either just appeared, or is just about to, however [adjacent image shows Hippopotamus (or Hexaprotodon) madagascariensis skeleton with H. amphibius skull].
And that is that. As I’ve said in previous articles, the 55th SVPCA was a highly enjoyable meeting; I even liked the in-jokes about palaeoichthyology and all those pachycormid talks. The civic reception, the whisky tasting, the annual symposium dinner, the auction, and those late-night meetings in kitchens and nightclubs made it an… interesting social event. More on SVPCA in the next article, this time focusing on obscure Wealden theropods (i.e., on my talk. Well, this is my blog).
Bat talk on Tuesday. Mmmm, bats…
Refs – –
Buffetaut, E., Grellet-Tinner, G., Suteethorn, V., Cuny, G., Tong, H., Košir, A., Cavin, L., Chitsing, S., Griffiths, P. J., Tabouelle, J. & Le Loeuff, J. 2005. Minute theropod eggs and embryo from the Lower Cretaceous of Thailand and the dinosaur-bird transition. Naturwissenschaften 92, 477-482.
Gould, G. C. & MacFadden, B. J. 2004. Gigantism, dwarfism, and Cope’s rule: “nothing in evolution makes sense without a phylogeny”. Bulletin of the American Museum of Natural History 285, 219-237.
Heinrich, R. E., Ruff, C. B. & Weishampel, D. B. 1993. Femoral ontogeny and locomotor biomechanics of Dryosaurus lettowvorbecki (Dinosauria, Iguanodontia). Zoological Journal of the Linnean Society 108, 179-196.
Hone, D. W. E. & Benton, M. J. 2007. Cope’s rule in the Pterosauria, and differing perceptions of Cope’s Rule at different taxonomic levels. Journal of Evolutionary Biology 20, 1164-1170.
– ., Keesey, T. M., Pisani, D. & Purvis, A. 2005. Macroevolutionary trends in the Dinosauria: Cope’s rule. Journal of Evolutionary Biology 18, 587-595.
Martill, D. M., Naish, D. & Earland, S. 2006. Dinosaurs in marine strata: evidence from the British Jurassic, including a review of the allochthonous vertebrate assemblage from the marine Kimmeridge Clay Formation (Upper Jurassic) of Great Britain. In Colectivo Arqueológico-Paleontológico Salense (ed) Actas de las III Jornadas sobre Dinosaurios y su Entorno. Salas de los Infantes (Burgos, España), pp. 47-83.
Naish, D. & Martill, D. M. 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, London 164, 493-510.
– ., Martill, D. M. & Frey, E. 2004. Ecology, systematics and biogeographical relationships of dinosaurs, including a new theropod, from the Santana Formation (?Albian, Early Cretaceous) of Brazil. Historical Biology 16, 57-70.
Wilson, J. A. & Sereno, P. C. 1998. Early evolution and higher-level phylogeny of sauropod dinosaurs. Society of Vertebrate Paleontology Memoir 5, 68 pp.