>The first dinosaurs evolved about 230 million years ago in the Triassic
>period. Early dinosaurs were generalists, and had evolved into no more than
>around 40 genera at any one time up until the late Jurassic, which began
>about 160 million years ago.
>
>Mesozoic dinosaur diversity
>But then diversity soared in the Cretaceous which followed (see graphic).
>Fastovsky's team has established that at least 245 dinosaur genera lived
>during the late Cretaceous period, from 99 to 65 million years ago.

But diversity means there was directional or diversifying selection pressure
that changed the
generalists into separate species. Correct?

If there had been stabilizing selection and these
dinosaurs were well adapted - then the pop would have grown for each species,
and change that comes from
directional or diversifying selection would have been small wouldn't it?   And
with the large general pop gene pool there would have been less genetic drift?

I suggest diversity (other than just evolving bigger for ex.) usually means
problems that have forced directional or diversifying selection.

Comment?

My model  
The greater the selection pressure (directional or
diversifying selection)  the greater the speed of evolution
and vice versa
The lower the selection pressure (mostly stabilizing
selection) the lower the speed of evolution.
---
þ RIMEGate(tm)/RGXPost V1.14 at BBSWORLD * Info{at}bbsworld.com

---
 * RIMEGate(tm)V10.2áÿ* RelayNet(tm) NNTP Gateway * MoonDog BBS
 * RgateImp.MoonDog.BBS at 10/16/04 9:48:47 PM