[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: Back-evolution of limbs.

I would like to insert a question here........ was the original limb composed
of five digits
before going onshore , or developed after becoming terrestrial ?
Earl Wood

Jeff Hecht wrote:

> 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