Re: a really big bite

[Colin McHenry <cmchenry@westserv.net.au>]

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 Unpublished 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