Re: Hell Creek and stegosaurs

["David Marjanovic" <david.marjanovic@gmx.at>]

----- Original Message -----
From: "Williams, Tim" <TiJaWi@agron.iastate.edu>
Sent: Monday, June 03, 2002 9:42 PM

> The fact that, at the very
> end, N. American terrestrial environments were dominated by a smaller
> number of dino species than previously may reflect local environmental
> factors.

And maybe the Manson impact 8 Ma before?

> _Dravidosaurus_ is probably not a stegosaur - or even a dinosaur.  I
> have heard that the scrappy material from southern India named
> _Dravidosaurus_ actually comes from a sea reptile (plesiosaur?)

Yes, it's a plesiosaur according to Glut's Encyclopedia, Supplement 2.

> > Only a handful of others made it into that same era.

Do you mean the Cretaceous?

> > So what happened
> > to them, climatic change, different predators/food?
>
> One theory is that stegosaurs, with their relatively unprotected flanks,
> were vulnerable to the new 'breed' of maniraptoran killers - especially
> deinonychosaurs.

That speculation is certainly wrong -- said killers were nothing new,
stegosaur tails should provide enough protection, and *Wuerhosaurus* lived
rather late in the EK. When exactly? Could I maybe blame the little
Aptian-Albian mass extinction? Or the Cenomanian-Turonian one (would imply
some ghost lineage)? :-) -- With the few known stegosaurs it's of course
rather improbable that we'll find out anytime soon why they died out before
the K-T, and when.