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Re: Sexual Dimorphism (was T.rex Q & A)

Berislav Krzic wrote:

[concerning sexual dimorphism]

<What about Psittacosaurus?>

  I'm sure work is being done of these fellows right now, but without
further info, I cannot say. However, since most psittacosaur material
is skulls and skull fragments and every new skull differs enough to be
a new species (or even new genus?), this is difficult at best to
gague. The way Proto, Chasmo, and Trikes are told apart won't work
with Psittaco due to the lack of such tell-tale features: nose-horn,
brow horns, and elongate frill. Now, there's some case, I remember,
for jugal horns, but I think Peter Buchholz and T. Mike Keesey (last
year) here said something about specific variation on that case.


  Two actual skulls (one with a skeleton), one with the fangs, one
without. Not a big enough sample size to detirmine anything. If there
was cause for dimorphism, the males would have tusks and the females
noty, similar to suids. [note: I said "similar".]


  I think the case here was the extra frill ornamentation and
concave/convex nature of the nasal boss, the first apparently a new
species (*P.* sp.?) while the other also without an approproiate or
published sample size to detirmine tit from tat.


  Unless *Ingenia* has been returned to *Oviraptor*, there is no case
here. Sure would've liked the nesting skeletons to have their heads
attached, but that was too much to ask for, wasn't it? :) No tails
except in *Ingenia* to discern that part, or specimens that have not
been published, and that one tail is just _one_ tail.

  *Oviraptor* skulls without crests (such as the juvenile in the
_Audubon_ issue with *Sinosauropteryx*) are too young to detirmine the
case, as they may develop the crest upon maturity.

Jaime A. Headden

Qilong, the website, at:
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