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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_