On to our second day of talks (read part I first): things kicked off with Mike A. Taylor and Angela Milner’s talk on the history and collections of Street. Pinpointing the locations of original quarries is always difficult as exact records are often not kept, and of course the areas once used for quarrying change function and appearance over time. One interesting point is that the concept of ‘Street’ as a locality should perhaps be interpreted as broadly as possible, given that certain other, nearby Somerset sources might sometimes have provided specimens too [adjacent photo by Mo Hassan of Disillusioned Taxonomist].
Dave Martill looked at the taphonomy of Mesozoic marine reptiles, and hence at such things as the role of carcasses as ‘benthic islands’ and the orientation of carcasses in the substrate. While discussing decomposition and putrefaction, he even showed a photo of the Zuiyo-maru carcass (though misidentified it, alas). Mike Benton spoke again about trends in diversity across the PTB and beyond, this time in tetrapods as a whole. This included his work on the rise of dinosaurs (and on how they were effectively ‘victors by default’), and on the recent work by Brusatte et al. (2008) on the changing fortunes of crurotarsans and ornithodirans during the Triassic. Lez Noè discussed plesiosaur diversity and palaeobiology, noting that their rarity in the Upper Triassic is most likely an artefact resulting from evolution in open waters that aren’t well represented by the sedimentological record. The few Triassic plesiosaur fossils we have (including those from Svalbard, Scotland and England) do suggest the presence of a ghost lineage for the clade that extends well back into the Triassic. Lez also focused on his proposal that long-necked plesiosaurs might have been benthic feeders that used the neck to reach down to the bottom. Lots to say on that, but I’ll wait until he’s published! [image below shows Kevin the temnodontosaur, as displayed at the Philpots Museum. Kevin was discovered by Paddy Howe (the museum's geologist) in 2005. Unfortunately, most of its skull is missing].
Ryosuke Motani looked at ichthyosaur evolution across the Triassic-Jurassic boundary. Traditionally, it’s been thought that fish-shaped ichthyosaurs (known today as parvipelvians) were uniquely Jurassic and Cretaceous, and that Triassic ones were less modified. New specimens and new work have shown that things were far more complex, and that the suite of characters involved in the acquisition of the parvipelvian-style tail were assembled piecemeal among non-parvipelvian taxa, and that the transition to a fish-like body shape occurred during the Triassic. So, there was no clear morphological turnover at the Triassic-Jurassic boundary… but was there a taxonomic turnover? Jurassic ichthyosaur taxa have yet to be reported from the Triassic (previous records of such are now known to be incorrect: recall that Macgowania was originally described as a species of Ichthyosaurus), but stem members of several lineages do seem to be present, as indicated by Ichthyosaurus-like, Leptonectes-like and Temnodontosaurus-like animals from British Columbia. It now seems that non-parvipelvians made it into the Jurassic, as demonstrated by a very interesting new taxon. A great talk, and the copious new data discussed therein is due to be published soon [image below shows a Jurassic marine contingent photographed at Lyme Regis. From left to right: Jeff 'Leedsichthys' Liston, Ryosuke Motani, Richard Forrest, Adam Stuart Smith].
Incidentally, a talk on marine crocodilians was conspicuous by its absence (though, admittedly, they don’t appear until the Toarcian and are hence somewhat younger than the strata at Street). This wasn’t an oversight: an effort had been made to include the group in the proceedings, but the two speakers who were approached were both unable to appear on the day.
The indoor element of the meeting ended with an open-floor discussion led by Michael Benton. A lot of historical stuff was thrashed out (I asked an intelligent question about the origin of the weird ichthyosaur on the road sign, but have forgotten the answer… Mike Taylor tells me that they’d lifted the pic from one of Thomas Hawkins’s books). Ella Hoch asked if Mesozoic marine reptiles ever evolved suction feeding analogous to that practised by extant beaked whales. It’s an open secret that a new ichthyosaur specimen with suction-feeding adaptations has been written up, but the authors have lost momentum on their paper after having it rejected (for unsound and retarded reasons) several times; it’s currently in limbo. It shows that at least some Mesozoic marine reptiles were ziphiid-like in terms of ecomorphology. Placodonts, pachypleurosaurs and at least one nothosaur all had suction-feeding adaptations similar to those of extant turtles. I’ve been saying for ages that I’ll elaborate on this at some stage… and at some stage I will. Meanwhile, see Rieppel (2002) [adjacent photo courtesy of Stig Walsh, taken outside the venue. Wow, so I do look like an australopithecine...].
Incidentally, for the duration of the meeting we had access to excellent marine reptile fossils, so got to see more than our fair share of Street’s plesiosaurs and ichthyosaurs. Many are beautifully preserved and fully or partially articulated, and some pose really interesting questions about taphonomy and preservation. Chris Moore and Simon Carpenter were also good enough to bring specimens along to the meeting, as were the Lyme Museum people [another temnodontosaur from Lyme Regis shown below (well, a cast: the real thing is too heavy to be wall-mounted like this). This specimen was found by Henry Ellis, donated to the museum in 1927, and prepared by David Costin in 1985. You're looking at the underside of the incomplete skull].
Things finished with a field trip or two. The original plan was to visit various quarries in the Street area, but this couldn’t happen due to rain (it is summer after all). Instead, we visited Charmouth and Lyme Regis, so we got to visit the Charmouth Local Heritage Centre, the Philpot Museum (see Taylor (1986) for a review of the Philpot collection’s history), Chris Moore’s workshop and house, and other places too. The Philpot Museum has various temnodontosaur and other ichthyosaur specimens on display, as well as a juvenile scelidosaur and some Dimorphodon material. Charmouth has – among many other things – a cast of the amazing new scelidosaur figured by Naish & Martill (2007) – shown below – and discussed here. We saw some brand-new stuff, including at least one new ichthyosaur species (I won’t say what it was).
I’ve done the whole palaeo-tourist thing along the Dorset coastline many, many times (a consequence of going to a university on the southern coast of England), but it was brilliant to see all of these specimens, and to do so in the company of so many experts and specialists. Hey: if you worked on Jurassic marine vertebrates and didn’t come along… where were you?
All in all, I feel that ‘Sea Dragons of Avalon’ was a great success. We had our themed Arthur Cruickshank day, hosted an outstanding public lecture, and saw an appropriate selection of technical talks that covered all aspects of Street’s geology and palaeontology [adjacent image shows Lias mural on display at Charmouth Local Heritage Centre]. We (by which I mean ‘I’) also had lots of beer and curry, and as usual I stayed up far too late, talking about Thundercats, La Roux, Duran Duran and Torchwood. Many thanks to Mike A. Taylor, Lez Noè and Adam Smith for assisting with the write-up you’ve just read, to Mike, Lez, Jeff, David Hill, Chris Moore, Paddy Howe, Simon Carpenter and others for organisation and access to fossils, to Jeff for driving me there and back, and to everyone else involved for making it what it was.
For previous articles relevant to some of the material discussed here see…
- SVPCA 2007: lepidosaurs, turtles, crocodilians, the plesiosaur research revolution continues
- A life secretly devoted to fish-lizards
- At the 56th SVPCA – hello Dublin!
- The skin of ichthyosaurs
- Sea Dragons of Avalon: a 2009 seminar
- In which Bob Nicholls exceeds expectations and produces some jolly good artwork
- The world’s biggest ever fish: time to put out the trash
- Sea Dragons of Avalon, an Arthurian adventure (part I)
And here’s that cake again, thanks to Lez Noè…
Refs – –
Brusatte, S., Benton, M. J., Ruta, M. & Lloyd, G. T. 2008. Superiority, competition, and opportunism in the evolutionary radiation of dinosaurs. Science 321, 1485-1488.
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.
Rieppel, O. 2002. Feeding mechanisms in Triassic stem-group sauropterygians: the anatomy of a successful invasion of Mesozoic seas. Zoological Journal of the Linnean Society 135, 33-63.
Taylor, M. A. 1986. The Lyme Regis (Philpot) Museum: the history, problems and prospects of a small museum and its geological collection. The Geological Curator 4, 309-317.