Therizinosaurs...and ME

[NJPharris@aol.com]

Hi, guys!  I was just reading through recent dinosaur digests to get
back into the swing of the list when I noticed a post from John
R. Wagner wondering where I've been.  Made me all misty-eyed to
realize you care ;-).
 The answer is that I've been home from college since the 19th of May
and hadn't gotten around to re-subscribing myself from this computer.
But I'm back.

The post I am referring to also talked about therizinosaur phylogeny.
I've been poring over all the relevant material I could find
(_Dinosauria_ articles on "segnosaurs" and other theropods,
description of _Alxasaurus_), and my guess is as follows:

Metatarsal II appears, at least in _Segnosaurus_, to overlap
metatarsal II on the top surface of the foot.  This is a canosaur or
ornitholestian trait.
 Metatarsal V is depicted as platelike.  This is less advanced than in
dromaeosaurs and _Archaeopteryx_.  The humerus of _Alxasaurus_, with
its long deltopectoral crest, is more like _Ornitholestes_ or a
carnosaur than it is like an arctomet or dromaeosaur.

The apparent triangular obturator process in _Alxasaurus_ (provided
the ischia have been correctly identified) would make therizinosaurs
coelurosaurs, rather than carnosaurs.  My guess is that therizinosaurs
are descendents of early, ornitholestian-like coelurosaurs.  In fact,
a few characters (small head, femur longer than tibia, decurved
dentary) may support a direct link between _Ornitholestes_ and
therizinosaurs.  But I'm not sure.

Nick Pharris
Olympia, WA
NJPharris@aol.com