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Re: a really big bite



john hunt wrote:
Cool. I thought Lipluroden was also Late Jurassic? I've dug out my old WWD
books and apparently the estimate was based on scaled up isolated bones (a
bone in Peterborough museum scaled up to 17-20m) plus a bit for luck.

Currently, /Liopleurodon/ contains only one valid species, /L. ferox/, which is restricted to the Oxford Clay (which is Callovian, not Oxfordian) So it's Middle Jurassic. With a maximum total length of 6-7 m, /L. ferox/ is also much smaller than even the comparatively well known /Pliosaurus brachyspondylus/, and is not even in the same league as /Pliosaurus macromerus/ (known from a reasonable amount of material, including the 3 m long Cumnor mandible on display at the Oxford University Museum).


The Peterborough vertebrae was originally estimated as possibly indicating a maximum length of 18 m, by comparison with the Harvard mount of /Kronosaurus/. However, there are a couple of problems with this estimate; (1) the Harvard mount is more than 2 metres too long - scaling the Peterborough vertebra by the revised, shortened length for the Harvard /Kronosaurus/ gives a maximum length of the Peterborough 'pliosaur' of less than 15 m; (2) the taxonomic identity of the Peterborough bone is far from clear; it kind of looks a bit like a pliosaur cervical, but it has some features that would be unusual for a pliosaur and I tend to think that the original ID as a sauropod caudal is probably correct after all (although this question should really be rexamined by someone who is familar with UK M. Jurassic pliosaurids / sauropods).

The Peterborough vert - giant pliosaur suggestion was in an conference abstract to the 40th Annual meeting of the Palaeontological Association: C. McHenry, D. Martill, L. Noè, and A. Cruickshank; Just when you thought it was safe to go back into the water: the biggest pliosaur yet (1996).

The taxonomy of Pliosaurus / Liopleurodon has been most recently revisted by Leslie Noè;

Noè, L. F. 2001. A Taxonomic and Functional Study of the Callovian (Middle Jurassic) Pliosauridea (Reptilia, Sauropterygia). Unpublished PhD Thesis. University of Derby.

Noè, L. F., D. T. J. Smith, and D. I. Walton. 2004. A new species of Kimmeridgian pliosaur (Reptilia; Sauropterygia) and its bearing on the nomenclature of /Liopleurodon macromerus/. Proceedings of the Geologists' Association 115:13-24.


Darren Naish has included several posts on giant pliosaurs in his Tetrapod Zoology blog;
http://scienceblogs.com/tetrapodzoology/2007/12/cumnor_monster_mandible.php




--
Colin McHenry
Computational Biomechanics Research Group http://www.compbiomech.com/
School of Engineering (Mech Eng)
University of Newcastle
NSW 2308

t: +61 2 4921 8879