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Drepanosauridae



>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?


Actually, the Drepanosauridae were archosauroMORPHs, but well outside the
clade Archosauria (=crocs & birds and their most common ancestor).  They were
further from true archosaurs than are the proterosuchids, Euparkeria,
Erythrosuchidae, etc.

The drepanosaurids (Drepanosaurus, Megalancosaurus, Dolabrosaurus, the
so-called "deep-tailed swimmer", and possibly some other forms: G. Olshevsky
pers. commun.) have derived hands and feet that look for all the world like
chameleons'!! Obviously a convergence, but also very different from anything in
the Dinosauria (at least until you get up to advanced trunk-climbing birds like
woodpeckers).


Based on these fossils, they seem to be truly arboreal (not scansorial)
reptilians with a beaky head at the end of a long neck.  Some have pictured
them as a chameleon-like form, with the head and neck shooting forth to grab
insects.  Weird, werid critters.

Thomas R. Holtz, Jr.
Vertebrate Paleontologist
Dept. of Geology
University of Maryland
College Park, MD  20742
Email:Thomas_R_HOLTZ@umail.umd.edu (th81)
Fax: 301-314-9661
Phone:301-405-4084