RE: Rauhut's Thesis

[rbi <rbi@dana.ucc.nau.edu>]

>This seems like a complicated process of reversals. I believe that the more
>parsimonious answer would be that the crests evolved seperately, as opposed
>to switching a gene off and on and off and on. I'm going to have to agree
>with HP Mortimer on this one.

Don't you think it is odd that three ceratosaurs outside of the Neoceratosaurs
have a double crest formed by the same bones and has the same form?  I can't
see this as just convergent.  Usually, convergent characters are analogous,
not homologous.  That is, they have the same function and may look alike, but
they have different morphology.  Compare pedal digit II on dromaeosaurs and
Noasaurus.  Both have the same function, however the morphology of how the
flexor tendon attaches is different.  In S. kayentakatae, D. wetherilli, and
D. sinensis, the crest is exactly the same in how it develops from the cranial
bones. So, I think it is not convergent.

>Now I'm confused. Are you saying it is a coelophysoid, or it is congeneric
>with _Dilophosaurus_?

I'm saying I think it is a ceratosaur.  I wouldn't go as far as calling it a
coelophysoid as in recent cladistic analysis D. wetherilli has fallen outside
of the Coelophysoidea, and D. sinensis is just plain weird.

Randall Irmis