Extinction Question and a Thank You!

[Dinosaur World <dinoworld@msn.com>]

Hi everyone. First let me thank all of you who submitted your ideas for 
future videos. I must say that I was amazed at the number of you wanted to 
see something on the evolution of mammals. Certainly we will make this a 
priority for a future show.

I need your help in understanding something about mass extinctions. It has 
been theorized that a dramatic change in world-wide climate was a catalyst 
for the extinction of species at the end of the Permian and Cretaceous. If 
indeed a dramatic climate change would have occurred, wouldn?t that have 
caused an accelerated evolutionary change in ALL life on the planet, since 
every environment on earth would have been impacted?

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? Wouldn?t a dramatic change in their environment demand that 
they would have to evolve to cope with it? In other words, shouldn?t there 
be a very recognizable difference between a pre- KT Crocodile and Post-KT 
Croc?

Could any of you give me your insight into this please?

Thanks for all of your help.

George Blasing
Dinosaur World Inc.