Re: AAT a bust

Phillip Bigelow (
30 Sep 1995 14:17:21 -0700

Someone wrote:
>Ss> It might also be noted that penguins who have evolved an
>Ss> aquatic lifestyle are also bipedal in their terrestrial locomotion, as
>Ss> are polar bears.

Bad examples. All birds are bipedal. Since the earliest bird fossils found
show bipedal traits, and since birds are believed to have evolved from a
terrestrial/arboreal? reptile (probably a theropod), then bipedalism in
birds is a terrestrial adaptation, and in addition, it is a plesiomorphy for
Avi-theropoda. Penguins therefore show the plesiomorphy in this instance,
and the trait is NOT aquaticly-derived.
Polar bear hip structure is identical to that of all other Recent Ursidae;
therefore, a land-locked grizzly is as "bipedal" as the polar bear.....
which isn't saying much.....