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In a message dated 95-12-08 14:23:41 EST, longrich@phoenix.Princeton.EDU
(Nicholas R. Longrich) writes:

>       Bakker thinks that Othnielia and his pet dino Drinker (relatives of 
>the hypsilophodonts, 5-6 and 2-4 feet respectively, Late Jurassic of 
>Colorado, Wyoming, and Utah/ Wyoming) were 
>both arboreal forms. He cites a large, opposable first toe, and noted 
>something about the ankles- I think it was that they could rotate. I'm 
>guessing that he was speaking about the reversible ankle thing.
>       I just checked out the ankles for myself, right out of my window. The

>squirrel's toes end up pointing directly out to the sides. 
>       Am I right in remembering that some pterosaurs also have reversible 

Bakker hasn't published anything on this yet, even in his _Hunteria_. In
fact, all that has been described of _Drinker_ are little bits and pieces. He
says he has something like 40 complete skeletons (really??), so where are

I have been wondering about laterally directed feet as an arboreal
adaptation. Something like this is present in _Drepanosaurus_, a small
Italian Triassic reptile in which the distal caudal vertebra(e?) is (are)
modified into a prehensile hook. It is most likely an archosaur but because
we have no skull we can't tell; a close relative is the controversial
_Megalancosaurus_, whose skull is considered by some to show archosaurian
traits (such as the antorbital fenestra). _Drepanosaurus_ feet seem to be
highly modified for arboreality, with opposable digits galore, and I think
the hind feet were laterally directed. The feet also had enlarged calcanea
such as are found in thecodontians. Synapomorphy, anyone?