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

Re: Extinction Question and a Thank You!

On Sat, 05 Feb 2005 22:56:42 +0000, Dinosaur World <dinoworld@msn.com> wrote:
> What I am not clear on is why there are so many modern animals that have
> retained the same basic design as their Permian and Cretaceous counterparts?
> If early Crocodiles, Alligators, Sharks, Insects etc. were subjected to
> global environmental changes that were long enough and strong enough to wipe
> out other species, why then do they still resemble their modern
> counterparts?

This assumption is difficult to quantify, and hence hard to test. I
wouldn't take it as a given. CMIIW, but I think the Cenozoic clades of
crocodylians and sharks arose during the Cretaceous, but were not
around during the Permian.

-- Mike Keesey