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GO writes:

>It's nice to be corrected in the BCF direction! Reversible ankles, you say?!
>Love it!

Reversible ankles are also found in two cats, the Margay and the Clouded
Leopard.  They permit a quadrupedal animal to descend a tree headfirst or to
hang from a limb by its hind feet while grasping prey (that's why a Margay
can come down a tree headfirst and a domestic cat can't).  They might not
show up in an arboreal theropod - after all many arboreal or partly arboreal
mammals (like other cats) don't have them, and they possibly would be less
likely in a biped (which could get down a tree by shinnying tail first or,
like a tree kangaroo, simply jumping out of it.)  I don't know any bird that
has such a structure.  However, if any such modification did show up in a
suitable theropod candidate (allowing for the general differences between
dino and mammal ankle joints - and them might be somewhere else on the leg
in a dino) it would be, I think, pretty good evidence of arboreality.
Ronald I. Orenstein                           Phone: (905) 820-7886 (home)
International Wildlife Coalition              Fax/Modem: (905) 569-0116 (home)
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