Megalosaur femora (was RE: New Megalosaurus paper)

[Tim Williams <twilliams_alpha@hotmail.com>]

> Day and Barrett, 2004. Material Referred to Megalosaurus (Dinosauria:
> Theropoda) from the Middle Jurassic of Stonesfield, Oxfordshire, England:
> one taxon or two? Proceedings of the Geologists' Association. 115, 359-366.


Day and Barrett (2004) report two different femoral morphotypes: "straight" 
(morphotype A) and "sigmoidal" (morphotype B).  They note that some of the 
differences between the two morphs are comparable to those listed for 
_Syntarsus_ (=_Coeophysis rhodesiensis_), which does show gracile and robust 
morphs.  However, they also say that _Syntarsus_ specimens do not show such 
"wholesale difference in overall femoral shape" (straight vs sigmoidal) as 
seen in the femora assigned to _Megalosaurus_.  Thus, Day and Barrett 
conclude that morphotypes A and B represent two distinct taxa.

To play Devil's Advocate....

I think femoral shape (straight vs sigmoidal) may actually vary in 
prosauropod specimens - even within the same individual.  I'll have to check 
my references, but I think at least one prosauropod species from Europe 
shows variation in the overall shape of the femur (straight vs sigmoidal).  
The difference is attributed to taphonomy, which can turn a sigmoidal femur 
into a straight one.  As I said, I'll have to check my references.

(Many thanks to Mickey for providing me with a copy of the _Megalosaurus_ 
paper.)


Tim