Re: Segnosaurs

["Tim Williams" <T.Williams@cclru.randwick.unsw.edu.au>]

> What?  You know of a study on segnosaur brains?  Last I heard, no one had
> done anything on segnosaur brains.

The article I read was an abstract in JVP, which said that there were
similarities regarding certain elements of the braincase between
segnosaurs and coelurosaurs (including birds).  I can't remember the
details though.  I'm pretty sure it didn't mention anything about the
brain itself.

> They fascinate everyone, but clearly, there are too too many features that
> segnosaurs possess that are also possessed by prosauropods, and too too many
> features they possess that are also possessed by coelurians to really make
> any definate conclusions, though I side for the prosauropod end myself.

To my mind, the segnosaurian foot is one sticking point for theropod
affinities.  In all theropods (including _Eoraptor_) the hallux is
reversed and assumed to be nonfunctional, producing a functionally
tridactyl foot.  Segnosaurs have no reversed hallux and have a
functionally tetradactyl foot, which (unless this feature is a
reversal) makes the foot more primitive than even _Eoraptor_ and the
herrerasaurids.

However, _Erlikosaurus_ is said to have an intramandibular "hinge" in
the lower jaw, like all theropods (including herrerasaurids, but not
_Eoraptor_ according to Paul Sereno).  But, despite the cranial
evidence, I also lean towards sauropodomorph affinities for the
Segnosauria.

Tim Williams