RE: how many species

["Williams, Tim" <TiJaWi@agron.iastate.edu>]

Nick Longrich wrote:

>Looking at modern diversity patterns, three or four species each of 
>Ceratosaurus, Archaeopteryx and Allosaurus seems perfectly possible 
>to me; while a single species of Troodon (T. formosus) throughout the 
>Late Cretaceous of North America seems just impossible- it'd be like 
>having all the cats or canids in North America from the Miocene on, 
>all in one species.

Ah, but in Recent times there was only one species of _Thylacinus_ across
the entire continent of Australia.  (Now, there's probably none at all.
Very sad...)

Despite the morphological variation displayed by the late Maastrichtian
tyrannosaurid material from North America, most workers recognise only one
valid species: _T. rex.



Tim