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Re: T rex brooding


    I don't know if dimorphism is an *accepted* fact in tyrannosaurs.
However, I have been working my way thru the 1996 DinoFest International
publication (printed this year for DinoFest here in Phila.).  Neal Larson
(BHI) has a paper which lists all the _T. rex_ specimens (21 at the time)
and he sees definite sexual dimorphism.  There are robust specimens with
relatively smooth skulls (those that have skulls) - these are presumed
female.  Males are presumed gracile and have rugose skulls.  And he has one
presumed male specimen ("STAN") that shows an additional caudal chevron
immediately behind the sacral vertebrae - as in crocodiles (the first caudal
chevron - used for penile retraction).  He surmises that female _T. rexes_
will not have that chevron - not yet tested.  There is also a paper by Ralph
Chapman, Dave Weishampel, Gene Hunt, and Diego Rasskin-Gutman that
summarizes Neal's findings on _T. rex_ and others' on other dinosaurs
("Sexual Dimorphism in Dinosaurs" - I looked it up).

    Allan Edels

-----Original Message-----
From: Stewart, Dwight <Dwight.Stewart@VLSI.com>
To: 'edels@email.msn.com' <edels@email.msn.com>; dinosaur@usc.edu
Date: Wednesday, August 19, 1998 4:56 PM
Subject: RE: T rex brooding

>dimorphism an accepted fact in tyrannosaurs?  I'm NOT disputing it, I was
>just wondering how much scientific evidence there is for it?
> Dwight