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Re: Tyrannosaur growth and babies



Dwight wrote  , on Dec. 8
> 
>       Thanks.  This made me think of  another question. :-)  How strong is
> the evidence for dimorphism in
>       Tyrannosaurus rex?  What brought this to mind was a conversation I
> recently had with a friend
>       regarding this subject.  That made me return to Dr. Horner's The
> Complete T. rex to see what it had
>       to say regarding potential dimorphism.  The book indicated that Dr.
> Bakker isn't sold on dimorphism
>       & (in fact) believes that the more robust specimens represent a
> different species.  If the only differences are size and bulk, then the
> different species hypothesis doesn't seem likely to me.
>       As an admittedly remote example, extant species vary more within
> themselves that the total
>       variation among known Tyrannosaurus specimens.  
> 
>       Dwight

Dwight , 
In  ' Dinosaur  Systematics ' (Currie & Carpenter , 1990 ) there's a
section on variation among T.rex specimens . All the examples show a degree
of variation from one another  , with the gracile morph exhibiting more
defined lachrymal / postorbital structures . This being indicative of a
male T.trex . Additionally , in ' Hunting Dinosaurs ' (Psihoyos & Knoebber
, 1994) , Pete Larson  elaborates on some research performed on crocodiles
, by Eberhart Freye . Larson found that sexual differences in crocs' caudal
vertebrae were similar to what is found in the two T.rex morphs . The
gracile morph ( male) has the first (and more robust ) chevron located
one vertebrae forward of the same chevron in the robust morph . Presumably
, this condition in the robust morph would allow more space for eggs to
pass between the tail and the ischia . My $0.02 worth. Next!
Hope this helps. 
Regards , 
Truett Garner