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maxillary fenestration & WHAT are "segnosaurs"?



Thomas and Mickey,
Thanks for the information. However, this does not ease my mind regarding segnosaurs at all (quite the opposite).
In fact, it brings up the question once again of whether segnosaurs are coelurosaurs AT ALL, or even if we can confidently place them among tetanurans.
I don't know whether the new "Nothronychus" will have any bearing on this problem (I surely hope so), but I am once again troubled by the status of the "therizinosaurians" (a possibly paraphyletic or even polyphyletic group) and whether or not some of them (segnosaurs, i.e. therizinosaurines, in particular) should be excluded from "coelurosaurians" or even "tetanurans".
----more skepticism from:
Ken Kinman
*********************************************************
From: "Mickey Mortimer" <Mickey_Mortimer11@msn.com>
Reply-To: Mickey_Mortimer11@msn.com
To: <dinosaur@usc.edu>
Subject: Re: maxillary fenestration (was "magical" feathers)
Date: Thu, 28 Jun 2001 09:10:36 -0700

Ken Kinman wrote-

> What coelurosaurs are known to have had maxillary fenestration, and
> is there a good chance that Erlikosaurus and Chirostenotes didn't have
such
> fenestration in their ancestry?
> Could this be a red flag that we need to look closer at the
assumptions
> that have resulted in the conclusion that they "lost" maxillary
fenestration
> from ancestors that "possessed" this character?


Almost every coelurosaur whose maxilla is known has maxillary fenestration,
as do most tetanurines. Coelurosaurs with such a fenestra include-
tyrannosaurids, ornithomimosaurs, compsognathids, Ornitholestes,
Proceratosaurus, Scipionyx, Caudipteryx, oviraptorids, Shuvuuia,
troodontids, "Chilantaisaurus" maortuensis, dromaeosaurids, Achillobator,
Bambiraptor, Sinornithosaurus, Archaeopteryx and confuciusornithids. In
addition, Dilophosaurus, Ceratosaurus, abelisaurids, Afrovenator,
Piatnitzkysaurus, Eustreptospondylus, Monolophosaurus and allosauroids have
maxillary fenestration. The only coelurosaurs without such fenestrae are
Erlikosaurus, Chirostenotes and enantiornithines (perhaps ornithurines too,
I haven't studied them too closely). As they are deeply nested in the
Coelurosauria and closely related to other taxa with maxillary fenestrae, it
is obvious they lost the character sometime in their evolution.


Mickey Mortimer
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