Voracious snub-nosed robber

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For shame, I have yet to cover Mesozoic marine reptiles in depth here at Tet Zoo: in another effort to bring balance, I here depict a skull of the awesome Jurassic pliosaur Simolestes vorax Andrews, 1909. The name means something like 'voracious snub-nosed robber'. This essentially complete skull, discovered with much of the rest of the skeleton, was found in 1990 in a waste disposal site at Dogsthorpe, Peterborough (Cambridgeshire, UK) and comes from one of the most famous units of Jurassic rock in the world: the Oxford Clay. Originally identified as a new specimen of Liopleurodon ferox, the Dogsthorpe Simolestes has since been described by Leslie Noè in his unpublished phd thesis and is today on display at Peterborough Museum (where this photo was taken). It was the subject of several articles - and a book - on its discovery and excavation (Dawn 1991, Duff & Chancellor 1991, Martill 1992, Martin 1992).

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Simolestes has a notably short mandibular symphysis (unlike other Oxford Clay pliosaurs), and was traditionally thought to have had dorsoventrally shallow jaws in which the big caniniform teeth radiated outwards like the spokes of a wheel. This configuration (present in the type specimen: adjacent image shows this, from Andrews' original monograph) is in fact due to compression, and the Dogsthorpe specimen actually looks pretty deep-jawed (though it's suffered from lateral compression so this is somewhat exaggerated). Though imagined by some to have been a sort of cookie-cutter that took chunks out of ammonites or big vertebrates (Martill 1991), Simolestes is interpreted by Leslie as a cephalopod specialist and indeed the Dogsthorpe specimen contained a large number of cephalopod hooklets (Martill 1992). It wasn't a particularly big pliosaur, with most remains indicating a total length of 6 m or less. However, a few fragmentary remains in old collections suggest that it grew larger. The big caniniform teeth, nostril and orbit are all obvious in the photo. For more images and information see the Simolestes page at the Plesiosaur Directory.

A couple of other Simolestes species have been named from India and France (a supposed African species turned out to be a teleosaurid crocodyliform), and alleged relatives come from Argentina. Where Simolestes fits within plesiosaur phylogeny is controversial, but that's a subject for another time.

For previous Tet Zoo plesiosaur articles see this SVPCA 2007 report, the Terminatator article, and the ver 1 articles on BBC News 24 and Life in the Oxford Clay sea.

I'm going out into the wilderness over the weekend; no pliosaurs alas but we're certainly going to see lots of other creatures.

Refs - -

Dawn, A. 1991. A rare pliosaur from the Oxford Clay. Geology Today 7 (1), 7-8.

Duff, K. & Chancellor, G. 1991. The Dogsthorpe Pliosaur. Peterborough Museum & Art Gallery, Peterborough.

Martill, D. M. 1991. Marine reptiles. In Martill, D. M. & Hudon, J. D. (eds) Fossils of the Oxford Clay. The Palaeontological Association (London), pp. 226-243.

- . 1992. Pliosaur stomach contents from the Oxford Clay. Mercian Geologist 13, 37-42.

Martin, M. 1992. Another piece in the jigsaur. Landscape Autumn 1992, 14-16.

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By Allen Hazen (not verified) on 19 Dec 2007 #permalink