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Therizinosaur feet



One of the major arguments made against including the
Therizinosauroidea in the Theropoda is that metatarsal I reaches the
ankle in these animals.  While that may be true, I feel I should point
out that mtt I apparently does not participate in the ankle joint.
According to the description of _Alxasaurus_ by Russell and Dong, the
proximal end of mtt I in _Erlikosaurus_ (sorry, Tom, it just looks
better to me that way) and _Therizinosaurus_ is deeply cupped to
recieve the side of the shaft of mtt II.  Digit I points away from the
other digits, as in all other theropods, rather than lying parallel to
them, as in prosauropods.

Russell and Dong make no particular mention of _Segnosaurus_, but my
guess is that the reconstruction I have of that species does not show
the metatarsus correctly assembled.  Either that, or, if mtt I really
does participate in the ankle joint in _S. galbinensis_, then such a
condition is likely an autapomorphy of that particular species.

Nick Pharris
Olympia, WA

P.S.  It's good to hear that there's a new reconstruction of the skull
of _Erlikosaurus_.  The old reconstruction of the cheek region was
truly strange.  If you want to see the skull as it is actually
preserved (i.e.  dorsoventrally squashed and missing much of the
suspensorium), check out David Norman's _Illustrated Encyclopedia of
Dinosaurs_.