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Re: Sexual Dimorphism in _Coelophysis_




On Tue, 26 Sep 2000, Jerry D. Harris wrote:

>    I'm not saying that the amount of displacement of Ghost Ranch bones is 
> huge, but it is certainly noticeable on many, many specimens, and it's 
> conceivable that the difference between statistically significant 
> measurement differences and statistical noise is there within the diagenetic 
> history of the fossils...
> 

I'm really glad Jerry made this most important point. I was going to
write a similar post about the possible dimorphism in Plateosaurus
feomora found by Weishampel and Chapman (Dinosaur Systematics volume).
They found that the Trossingen femora formed two clusters, one lot had
craniocaudally expanded distal femora and broad caudofemoralis longus
attachment sites while the second showed mediolaterally broad distal
ends and narrow cfl attachments. It was speculated that this MIGHT be
sexual in origin. After looking at the Trossingen material myself I
believe that compaction is the probable culprit. Specifically those
femora that happened to be lying face up (or down) when buried became
compressed front to back (which also compressed the cfl scar) while
those that were lying on their sides became compressed from side to side
(with the cfl scar being largely unaffected).
Hopefully the mass of largely uncrushed Thecodontosaurus bones we have
in our lab can answer some of the questions about early sauropodomorph
dimorphism.

cheers

Adam Yates