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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
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.