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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.
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.