I said I wouldn’t do any conferences this year. But I lied, and have recently returned from the 58th Symposium on Vertebrate Palaeontology and Comparative Anatomy (SVPCA), this year held once again in Cambridge, UK. Compared to the enormous, sprawling SVP (= Society of Vertebrate Paleontology) meeting with its numerous concurrent sessions (last year held in England, but usually held in North America), SVPCA is tiny and tidy. So, ok, there’s less content, but at least you get to talk to everyone you want to, and to go to all the talks. As usual, I had an excellent time and extend warm thanks to the friends and colleagues who made it both fun and interesting.
Here, then, are just a few comments on some of the personal highlights. I’ll go through them in approximate chronological order (as in: Palaeozoic, Mesozoic, Cenozoic). First of all, it goes without saying that we spent a lot of time at the University of Cambridge’s Museum of Zoology. It’s outstanding, housing hundreds of skeletons and preserved specimens of everything from caecilians and lungfishes to indricotheres, giraffes and beaked whales. I took a lot of photos, one or two of which are shown here [Mirounga leonina shown below... wow]. Anyway, to business…
Tim Smithson and Stan Wood discussed an assemblage of new small stem-tetrapods discovered in sediments dated to the Tournaisian, and hence to the infamous ‘Romer’s Gap’ (a latest Devonian-early Carboniferous span of time, (mostly*) mysteriously devoid of tetrapod** fossils). Evidence for terrestrial arthropods was found in the same deposits. The discovery casts doubt on the hypothesis that terrestrial tetrapods and arthropods didn’t exist in Romer’s Gap due to low atmospheric oxygen content (Ward et al. 2006).
* But not entirely. See Clack (2002) and Warren (2007).
** The term Tetrapoda is used by some authors for the crown-clade that includes all extant tetrapods (and all descendants of their most recent common ancestor). If this is followed, the limbed sarcopterygians outside crown-Tetrapoda are termed either tetrapodomorphs or stem-tetrapods. Tetrapod in the phylogenetic sense is not necessarily, therefore, synonymous with tetrapod in the morphological sense.
Sauropods were comparatively well represented at the meeting with something like seven talks. Four of these were on neck posture and evolution, prompting John Hutchinson (the session chair) to refer to Neck Wars. Two talks were a direct response to the paper Mike P. Taylor, Mathew Wedel and I published last year (Taylor et al. 2009). Awesome: this is how science works [one of the figures from Taylor et al. (2009) is shown here. X-ray data shows elevated necks and neck bases in squamates, crocodilians and turtles: not just in mammals and birds].
In the first of those talks, John Martin looked at neck posture in extant animals. He aimed to show that some living animals do indeed adopt poses resembling those that emerge from osteological neutral pose (ONP). He therefore argued that ONP might really be a useful guide to ‘habitual pose’ or ‘characteristic pose’ (as in, the pose an animal is often seen to adopt). But I don’t agree, for two reasons. (1) ‘Habitual pose’ as used by Taylor et al. (2009) and preceding authors means alert pose (the pose an animal adopts when unrestrained, awake, and unengaged in any particular behaviour), not feeding pose, or running pose, or anything like that. Even if sauropods did hold their necks low or horizontally when feeding or drinking (something that everyone thinks they did), it does not follow that their ‘habitual pose’ was also low or horizontal. (2) John used photos of numerous museum-mounted skeletons to demonstrate that ONP replicates life posture. But mounted skeletons (which are posed with their necks held at the same angle as those of living animals) do not depict life posture at all (you need x-rays to determine this: remember that actual neck skeleton posture is more elevated than the soft tissues seem to imply), nor are they in ONP! The last point was well made in Taylor et al. (2009): when you plug vertebrae together to reproduce ONP, you do NOT get ‘habitual pose’.
In a related talk, Kent Stevens took issue with various of the statements made in Taylor et al. (2009), and used new (and excellent) CG models to depict possible neck postures and ranges of motion. He still regards sauropod neck pose to be more horizontal than we do, and his models permit less range of motion between the vertebrae than we consider likely. One of Kent’s points was that – even with a near-horizontal neck – a sauropod like Apatosaurus is still capable of reaching upward somewhat by bending the front part of its neck up above the height of its shoulders. But the possibility of an elevated neck base still seemed disallowed, and this is an obvious point of contention. Kent says that sauropods preserved with such neck bases are in death poses and exhibit extreme opisthotonic postures, whereas other people refer to evidence indicating that such postures were definitely ‘habitual’ in life. We made a point of showing (Taylor et al. 2009) that elevated neck bases are present in squamates, testudines, crocodilians* and neognathous birds (not just ostriches!!), so Kent’s implication that we only used rodents, rabbits and cats was a bit misleading.
* And we didn’t get x-ray data on the most erect-necked of crocs.
Andreas Christiansen and Gordon Dzemski used neck biomechanics in an effort to analyse neck posture and concluded that erect neck postures were likely for Euhelopus and brachiosaurids. In fact, they found that – when resources were far apart – maintaining the neck in an erect pose was more efficient in term of energy expenditure than were other postures. Andreas also noted that the anatomy and range of movement present in sauropod necks makes low habitual postures unlikely, and he was amusingly critical of the Stevens & Parrish (1999) horizontal-necked hypothesis (as shown in Andreas’s cartoon, used above).
To prove that we’re all still friends and get along fine, we all went to dinner together, though the ensuing discussion ended in a brawl after Mike made an offensive comment (see adjacent photo, kindly taken by Adam Smith). Further thoughts on the Neck Wars can be seen here on SV-POW!
Mike P. Taylor examined necks as well, but he was more interested in working out why sauropods have been so good at evolving tremendously long necks while other terrestrial tetrapods have never been able to get beyond a ‘glass ceiling’ of c. 3 m. Pneumaticity, quadrupedalism, reduced reliance on oral processing and other factors combined to allow the evolution of extreme necks in sauropods: the absence of some or all of these factors have seemingly prevented giraffes and other non-sauropods from becoming quite so ridiculous.
OK, gotta stop there. More in part II!
For more on sauropod necks, see…
- Junk in the trunk: why sauropod dinosaurs did not possess trunks
- Sauropod dinosaurs held their necks in high, raised postures
- Thunder-Lizards: the Sauropodomorph Dinosaurs (a book review)
Refs – -
Clack, J. A. 2002. An early tetrapod from ‘Romer’s Gap’. Nature 418, 72-76.
Stevens KA, & Parrish JM (1999). Neck posture and feeding habits of two jurassic sauropod dinosaurs Science (New York, N.Y.), 284 (5415), 798-800 PMID: 10221910
Ward, P., Labandeira, C., Laurin, M. & Berner, R. A. 2006. Confirmation of Romer’s Gap as a low oxygen interval constraining the timing of initial arthropod and vertebrate terrestrialization. Proceedings of the National Academy of Sciences 103, 16818-16822.
Warren, A. 2007. New data on Ossinodus pueri, a stem tetrapod from the Early Carboniferous of Australia. Journal of Vertebrate Paleontology 27, 850-862.