Re: "Dinosaurs Died Within Hours After Asteroid Hit Earth..."

[K and T Dykes <ktdykes@arcor.de>]

Hi Dora,

<<I understand that a viable theory exists that all modern mammals are
descended from a cow-sized herbivore that survived the extinction.>>

This isn't a viable theory, in my non-humble opinion.  The Upper Cretaceous
is characterized by, among other things, the complete absence of any
cow-sized mammals.  There are some possibly Cretaceous ungulates around,
(eg. Protungulatum).  However, they're nowhere near cow-sized and more
frequently found in Paleocene rock.

If our Protungulatum friend was directly ancestral to any existing mammals,
this would have been ungulates.  Placental mammals were already diverse
before the K-T extinction(s), although no existing orders of that have been
unequivocally evidenced (yet).  The speed of their radiation in the
Paleocene suggests some were probably already around though; insectivores,
primates, carnivores of some kind or other and ungulates among them.

In the absence of any Upper Cretaceous cow-sized herbivores, I don't feel
inclined to speculate on the lifestyle.  I could offer some warren-dwelling
hervibores from the Lower Triassic of South Africa, (Trirachodon).  This
genus is totally irrelevant, hamster-sized and non-mammalian.  However,
well-preserved burrow complexes from the Lower Triassic don't grow on trees,
so I thought I'd mention it.  Heck, they're cuter than Shirley Temple, and
she keeps getting on telly.
Cheers
Trevor

Mesozoic Eucynodonts
http://home.arcor.de/ktdykes/meseucaz.htm