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Re: Cretaceous mammals



Ralph Chapman wrote:

> > We all want lots and lots
> > of mammals if, for anything, to show just how pathetic the group was

> > during the day of dinosaur ;-). And besides, dinosaurs are still
more
> > diverse, species-wise.

Jim Kirkland wrote:
>    Not much so; perhaps a preservational bias.    At the Fruita Paleo
Area
> (Late Jurassic), there are at least 12 mamal species represented by
skulls and
> it is clear they vastly out number dinosaurs in abundance if not
biomass (8-)).
> Basically dinos and mammals fill different guilds. Dinos the big
carnivore
> herbivore guild and mammals the nocturnal insect-eater &
seed-collector guild,
> which most mammal species still do today. Small dinos are rare
(Echinodon &
> compsognathid size) and a diversity of cursorial crocs make up the
bulk of
> small predators (skunk- fox sized). Lizards and sphenodontids are the
diurnal
> insect-eater & seed-collectors.


Bird species are kicking mammalian butt in the Cenozoic, but
we mammals appear to have held our own in terms of
species diversity, (at least compared to non-avian dinosaurs)
back in the late Maastrichtian.

Check out this URL for a comprehensive listing of the Mammalia
vs. Dinosauria from the Hell Creek local fauna (sensu Archibald):

http://www.dinosauria.com/jdp/misc/hellcreek.html

The named mammals = 31 species (so far).
Both named and unnamed dinosaurs =  31 species (so far).

In fact, if you look closely at the dinosaur taxa in the list,
it could be that 31 species may be an optimistic
number for the Hell Creek Dinosauria (particularly the non-avians).
Of course, avian dinosaurs are undoubtably taphonomically
biased toward non-preservation, so who knows how many
avians were around during Hell Creek deposition.

(BTW: I strive to be accurate. If anyone notices something
wrong, outdated, or strange in the list, please let me know.)

                              <pb>