RE: Rauhut's Thesis

["Rob Gay" <rob_redwing@hotmail.com>]

> And, I would expect this if there is a specific or generic separation
> between taxa.  Now, the difference between Dilophosaurus and
> Monolophosaurus, is definitely convergent, as the crests are formed by
> different bones and have a completely different morphology.<
Is the ridge (which is more appropriate in the description of
_Monolophosaurus) actually formed from different bones? My photos of a mount
don't show enough detail in the skull to determine this. Personally, I would
expect us to see the differences beween _D. wetherilli_ and "D." _sinensis_
expressed as-is, in development of _dual_ crests, not a singular ridge as in
_Monolophosaurus_.

Also, I didn't get this original message, so I'm not sure if it was intended
for the list or not, but HP Headden wrote some of the following, and some of
the following is the responses from HP Irmis:
> such cranial specializations are horribly subject to environmental
pressures, and not gene flow<
I would agree. Ceratosaurs are not the only theropods to develop cranial
ornamentation. Tyrannosaurs and spinosaurs both have limited ornamentation.
And lets not forget cassowaries...

> Cranial ornamentation is not useful in phylogeny when comparing distantly
> related taxa with ornamentation that is morphologically different.<
As HP Headden points out above, it may not be useful at all.

> And I follow Downs (2000) synonymization of S. rhodesiensis with the genus
> Coelophysis.  Therefore, these "ridges" are probably homologous.<
This I would agree with.

Peace,
Rob

Student of Geology
Northern Arizona University
Biological Science Tech
Manti-La Sal National Forest
AIM: TarryAGoat
http://www.geocities.com/elvisimposter/dinopics.html
http://www.cafepress.com/RobsDinos
"A _Coelophysis_ with feathers?"

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