In the previous article on the 58th Symposium on Vertebrate Palaeontology and Comparative Anatomy (SVPCA), held in Cambridge, UK, I discussed some of the work that was presented on stem-tetrapods and sauropods. This time round, we look at more Mesozoic stuff – pterosaurs in particular – before getting on to Cenozoic mammals.
Steve Sweetman presented the first outing of a new miniscule maniraptoran theropod that he and I have been working on. When it gets published, nothing will ever be the same again (massive hyperbole fully intended: Steve’s talk was more to do with salamanders, anurans and lizards). Having mentioned lepidosaurs, Neil Curtis (et al.) and Marc Jones (et al.) presented some great analyses of skull function in Sphenodon.
Mesozoic marine reptiles weren’t tremendously well represented, but Mark Evans and Roger Benson’s new look at Lias Group plesiosaurian diversity was pretty neat: here was yet another study showing that Lias plesiosaurian diversity was higher than previously thought. It seems that Thalassiodracon hawkinsi is not, after all, the only small-bodied plesiosaurian in the Lias assemblage. Mark Purnell and Nia Roderick used microtextural analysis to show that the big pliosaur Simolestes was most likely not a cephalopod specialist as has been suggested, but that it wasn’t much different in diet from Liopleurodon.
Morganucodontids, Australasian spinosaurids, ornithischian hindlimb and pelvic musculature and the distribution of pneumaticity in theropods formed the focus of other Mesozoic talks. Michael Pittman illustrated the morphological changes that occurred during maniraptoran evolution as tails changed in shape and flexibility.
David Norman discussed his views on British iguanodontian taxonomy: he accepts the validity of Mantellisaurus but doesn’t regard Dollodon as distinct [adjacent Mantellisaurus reconstruction by Steveoc86, from wikipedia]. Furthermore, he reiterated his opinion that the Old Roar Quarry iguanodontian is referable to Barilium dawsoni (Norman 2010). I find this hard to believe because (despite extensive reconstruction of the right ilium) the former has a peculiar, sinuous dorsal iliac margin that makes it look quite different from the B. dawsoni holotype ilium (there are other differences as well – like taller neural spines in the Old Roar Quarry specimen – but it’s not clear how significant they are. Norman says that the sinuous iliac margin is due to post-mortem deformation [UPDATE: I'm going to backtrack here. New observations lead me to think that he's right]). Anyway, what with the recent naming of Owenodon and Kukufeldia, it’s clear that the once lamented wastebasket status of Iguanodon sensu lato (Naish & Martill 2008) is finally being resolved. What was meant to be one genus lasting for something like 30 million years is turning out to be at least five distinct ‘genera’, none of which were around for more than five million years. Incidentally, the Old Roar Quarry iguanodontian is of special interest (to me!) because of its claimed link to the Piltdown hoax (Naish 2008).
The stuff on pterosaurs you’ve all been waiting for
Few SVPCA talks on pterosaurs might be predicted given the very recent Flugsaurier 2010: Third International Symposium on Pterosaurs meeting in Beijing, but there were one or two revelations nonetheless. Dave Unwin’s talk was pretty incredible: a new Darwinopterus specimen is preserved in direct association with an egg (the egg is positioned as if just emerging from the pelvis, an event that almost certainly happened post-mortem). The Darwinopterus specimen concerned lacks a cranial crest (unlike other individuals of the same species), allowing us to make confident conclusions about sexual dimorphism in this (and other?) pterosaurs. At this point I will resist the urge to say any more.
Colin Palmer gave a very interesting talk on the flight position of pterosaur wings. Due to the position of the centre of gravity, he had to get flying pterosaurs to hold their wings in a ‘swept forward’ posture, quite different from that traditionally imagined. At the moment I’m sceptical, because it would create a very ‘pointed’ wing-tip somewhat different from what seems to be present in preserved soft tissues. But let’s not forget that not all pterosaurs are the same, and that what might apply to ornithocheirids does not necessarily follow for, say, rhamphorhynchids or anurognathids or whatever.
Azhdarchid pterosaurs are all the rage these days, ever since those Witton and Naish guys published that excellent paper (Witton & Naish 2008) [one of many newspaper articles shown in image above: look for typos. Image directly above - an adapted version of a Mark Witton piece - from The Paleochick's Digs]. The inferred strong terrestriality of azhdarchids, combined with the more realistic mass estimates that are now kicking around (Witton 2008), means that the possibility of azhdarchid flightlessness has recently been speculated about on a few occasions. While Witton (and Naish) favour a mass for big azhdarchids of 250 kg or so, Don Henderson recently proposed c. 540 kg for Quetzalcoatlus northropi, and therefore suggested that Q. northropi might have been flightless (Henderson 2010). This formed the topic of his talk. In my opinion it’s good to see someone else being highly critical of the absurdly low masses that have traditionally been given to pterosaurs large and small. With regard to the 70 kg apparently regarded as likely for Quetzalcoatlus by many authors, Don said “I would love to know what they’ve been smoking” (with the ‘they’ being the pterosaur workers, not the pterosaurs).
While most of us tend to assume that flightlessness for azhdarchids is contradicted by what we know of their skeletons, the fact remains that Q. northropi is very poorly known, perhaps allowing the possibility that it had reduced wings. However, the overall robustness and muscle attachment sites of the humerus are, I should think, still indicative of flight ability. I also think that the c. 540 kg mass estimate is too high: Don based his computational model on an incorrect template, but he knows this and is working to test things further. We might come back to this subject again.
Where the desmostylians are
Cenozoic mammal talks included those on rodent cranial anatomy, Oligocene sirenian diversity and the mechanics of gulp-feeding in mysticetes.
Vera Weisbecker (with Anjali Goswami) looked at brain size across marsupials and placentals: comparisons show convincingly that marsupials are NOT consistently smaller-brained than same-sized placentals. The idea that they are results from skewing by primates. Interestingly, marsupial brain size is not correlated with basal metabolic rate (in contrast to placentals) but seems more to do with extended lactation. This work (which looked at brain size and development in birds too) has just been published in PNAS (Weisbecker & Goswami 2010).
Desmostylians – a neat and bizarre group of afrotherian mammals that really should be covered on Tet Zoo some time – were the subject of Shoji Hayashi et al.’s talk. As everybody knows, the lifestyle, diet and even appearance of desmostylians has been controversial. At one extreme, some authors have interpreted them as terrestrial quadrupeds that foraged on exposed shores. At the other, some have regarded them as pinniped-like marine animals that only visited land for resting and basking. Thin-sections and CT scans from the ribs and limb bones of diverse desmostylian taxa show that they are not all alike: some exhibited osteosclerosis or pachy-osteosclerosis and most likely relied on static buoyancy in shallow water, while one (Desmostylus) exhibited osteoporotic bones and likely used dynamic buoyancy in deep water. Desmostylus may thus have been a pelagic, deep-water animal, in contrast to the other taxa (though it’s only fair to note here that this is in contradiction to conclusions drawn from isotope analysis: Clementz et al. (2003)). Oh, and if you want to know the story behind the orange cartoon character used at the very top, I recommend you visit this article at The Aquatic Amniote.
So, neat stuff. Loads more happened and I’d love to talk about it, but time is a real factor. I hope you enjoyed this quick look at (some of) the edited highlights. If you want to know more, the abstracts from the meeting are online at the SVPCA site here. Oh, and those of you who have previously seen this photo (humans included are Stephanie Pierce, Lionel Hautier, John Conway, Mathew Wedel, Michael P. Taylor, Stig Walsh, Robert Nicholls and Julia Molnar)…
… and want to know what everyone is gawping at.. well, here is the answer. It’s John Conway’s Jehol Biota zoom scene…
For previous articles on azhdarchids (flightless or not) and other pterosaurs see…
- The Wellnhofer pterosaur meeting, part I
- It could look a giraffe in the eyes
- The Wellnhofer pterosaur meeting, part II
- The Wellnhofer pterosaur meeting, part III
- Terrestrial stalking azhdarchids, the paper
- Shemhazai and other flightless pterosaurs
- Come back Lank, (nearly) all is forgiven
- Pterosaurs breathed in bird-like fashion and had inflatable air sacs in their wings
- Darwinopterus, the remarkable transitional pterosaur
- Giant pterosaurs invade London, Summer 2010
- Pterosaurs, err, indoors (the Summer 2010 exhibition)
Such plesiosaurs as Thalassiodracon and Simolestes have previously been discussed here…
- Voracious snub-nosed robber
- Sea Dragons of Avalon: a 2009 seminar
- Sea Dragons of Avalon, an Arthurian adventure (part I)
- An Arthurian adventure, part II: more fossil marine reptiles than are good for your health
And for more on iguanodontians, see…
Refs – -
Clementz, M. T., Hoppe, K. A. & Koch, P. L. 2003. A paleoecological paradox: the habitat and dietary preferences of the extinct tethythere Desmostylus, inferred from stable isotope analysis. Paleobiology 29, 506-519.
Henderson, D. (2010). Pterosaur body mass estimates from three-dimensional mathematical slicing Journal of Vertebrate Paleontology, 30 (3), 768-785 DOI: 10.1080/02724631003758334
Naish, D. 2008. Conan-Doyle [sic], Piltdown, and the dinosaur in the well: obscure Wealden dinosaurs and the stories behind them. In Moody, R., Buffetaut, E., Martill, D. & Naish, D. (eds) Dinosaurs and Other Extinct Saurians: A Historical Perspective. Abstracts of Meeting Held on the 6-7 May 2008. Geological Society of London, London, pp. 8-9.
- . & Martill, D. M. 2008. Dinosaurs of Great Britain and the role of the Geological Society of London in their discovery: Ornithischia. Journal of the Geological Society, London 165, 613-623.
Norman D. B. 2010. A taxonomy of iguanodontian (Dinosauria: Ornithopoda) from the lower Wealden Group (Cretaceous: Valanginian) of southern England. Zootaxa 2489, 47-66.
Weisbecker, V. & Goswami, A. 2010. Brain size, life history, and metabolism at the marsupial/placental dichotomy. Proceedings of the National Academy of Sciences 107, 16216-16221.
Witton, M. P. 2008. A new approach to determining pterosaur body mass and its implications for pterosaur flight. Zitteliana B28, 143-158.