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Re: HERBIVORES HAVE HALLUX TOO..



In a message dated 95-11-27 18:44:51 EST, ornstn@inforamp.net (Ronald
Orenstein) writes:

>On this point - the living species have, apparently convergently, evolved a
>highly-specialized ankle joint that allows them to reach into crevices and
>holes on vertical trunks from almost any position.  It occurs to me that the
>presence of such a joint in a small theropod might well be a strong
>indicator of arboreal foraging of this type.

One problem would be to get everyone to agree on the mechanics of a
fossilized ankle.

All the small theropod ankles I've seen are the very simple anteroposterior
hinge joint with a big astragalus, a little calcaneum, and some gravel-like
distal tarsals that are usually lost.

It's odd, by the way, that the astragalus remained separate from the tibia,
though firmly fixed to it, in most theropods. It only fused to the tibia
after birds became fully volant.