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Megalosaur femora (was RE: New Megalosaurus paper)




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