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Spinosaurian Choana



On Fri, 9 Oct 1998, Thomas R. Holtz, Jr. wrote:

> >Perhaps someone could say what a choana is too?
> 
> Sorry, let that one slip out. Internal nostril (the opening inside the roof
> of the mouth at the other end of the nasal passage).  In mammals and our
> ancestors, birds, and modern crocs it is far back in the throat; in most
> other reptiles (including non-maniraptoriform, and non-spinosaurid,
> theropods) it opens closer to the front of the mouth.

Hmmm... there are other similarities between spinosaurs and
maniraptoriforms, too (the teeth, for one). Seems like there's some
confusion between the clades (_Irritator_ being mistaken for a
bullatosaur, _Archaeornithoides_ being mistaken[?] for a spinosaur). 
Pretty weak "evidence", I know, but it does cause me to wonder -- what
exactly is it that keeps spinosaurs from being avetheropods closer to
maniraptoriforms than carnosaurs are? (Which would make them basal
coelurosaurs, wouldn't it...) 

--T. Mike Keesey                                   <tkeese1@gl.umbc.edu>
DINOSAUR WEB PAGES -- http://www.gl.umbc.edu/~tkeese1/dinosaur/index.htm