Deinonychus claws

[Jonathon Woolf <jwoolf@erinet.com>]

I hope nobody minds if I return to a topic that was discussed a month or
so ago, concerning the use of _Deinonychus's_ huge foot-claws.  At that
time, I offered the thought that perhaps the claw was roughly analogous
to a cat's claw, and might possibly have been used for climbing either
instead of or in addition to any hunting function.

A few days ago I bought a book about fossil cats (THE BIG CATS AND THEIR
FOSSIL RELATIVES, Alan Turner 1997).  While leafing through it last
night, I came across a sketch of a certain fossil mammal that showed a
*very* interesting feature on its forefeet.  Each foot had four toes,
and the innermost toe bore a very large sickle-shaped claw that was
apparently held clear of the ground while the animal was walking.  The
similarity to a dromaeosaur's inner claw is quite striking.

What was this animal?  It was _Thylacoleo_, the marsupial "lion" of
Pleistocene Australia.  It's clearly carnivorous, the caption says, but
as best anyone can tell it's descended from the phalangerids, a group of
marsupials whose living representatives are largely arboreal.  

I find it interesting that the nearest nondinosaurian analog to
_Deinonychus's_ giant foot-claw is found on the foot of an animal that,
if not itself arboreal, is descended from an arboreal ancestor.  

-- JSW