Re: Crocodile Rock

David Froehlich (
Wed, 18 Oct 1995 14:49:26 -0500

On 18 Oct 1995 wrote:

> chris brochu <> wrote:
> >1. They are very large (i.e. hippos), or
> >
> >2. they swim very, very well (i.e. otters), or
> >
> >3. they can get out of the water in a real hurry (i.e. ducks).
> >
> Put when the ancestral animal first crawled into the sea that would give
> rise to the seal species we have today, I very much doubt it had any of
> these three features either. And it survived.

Pinnipeds are derived from separate clades of the carnivores (it is
actually a polyphyletic grouping) and probably evolved in the Oligocene
or Miocene, possibly in the north pacific. You should note that they
probably evolved from a quadrupedal semi-terrestrial ancestor analogous
to the otter (although, I think this is mostly speculation) and that they
thus may fall into Chris' second category. Your analogy breaks down
because the hominids are bipedal/quadrupedal like all primates (at least
at a guess) and thus there is no exaptation for aquatic lifestyle.

Also, Chris' example is from modern environments and almost certainly the
biome was more different 50 million years ago (when the whales did it)
or +- 30 million years ago (presumably when the pinnipeds did it) than
5-8 million years ago (when the putative AAS ancestor did it). (I know
analogy again, I will reform when Hubey makes his time machine).

David J. Froehlich Phone: 512-471-6088
Vertebrate Paleontology Laboratory Fax: 512-471-5973
J.J. Pickle Research Campus
The University of Texas, Austin, Texas 78712