Re: Back-evolution of limbs.

[Jeff Hecht <jhecht@world.std.com>]

After I wrote:
>> But marine mammals and reptiles _have_ returned to their ancestral
>medium,
>> the sea, and the flippers of an ichthyosaur or dolfin resemble the
>fins of
>> fast predatory fish, e.g. sharks.

Larry Dunn asked:
>My understanding is that both the earliest reptiles and the earliest
>mammals were purely terrestrial forms, so I am confused.  What do you
>mean?

What I was trying to say -- but didn't say very clearly -- was that all
amniotes had descended from lobe-fin fish, which originally evolved their
limbs as fins. When they came on land, they evolved legs. When some of
their descendants returned to the sea, their adapted their legs back to
flippers -- essentially fins. -- Jeff Hecht