Tyrannosaurs and Carnosaurs in Morrison

[Larry Dunn <majestic_cheese@yahoo.com>]

---tsg94001@uconnvm.uconn.edu wrote:

> _Stokesosaurus_ of the Morrison
> Formation of Utah (Cleveland-Lloyd Quarry I believe) is a possible
> tyrannosaurid.  Madsen thought _Stokesosaurus_ was a tyrannosaurid
back in
> 1974 based upon the design of the ilium.  More recently (1998) Dan
Chure
> tentatively referred to _Stokesosaurus_ a partial braincase from the
same
> locality which is strikingly tyrannosaurid-like (UUVP 2455).

All this talk of Morrison tyrannosaurids is really interesting.  It
raises some questions, at least in my amateur's mind.

I had assumed that carnosaurs declined at the end of the Jurassic
either because:

1) prey they were adapted to hunt became extinct in Asiamerica due to
changes in flora; or

2) (a more recent assumption), because of the intervention of one of
those bolide things or some similar malevolent deus ex machina, which
killed off larger animals and allowed radiation by "marginalized"
groups.

Well, *if* there were tyrannosaurids in the Morrison, what does that
mean to this analysis?  

Could it be that tyrannosaurids ultimately out-competed carnosaurs?  I
mean, there were no carnosaurs in Asiamerica in the Cretaceous, were
there?  Just coelurosaurs of various types, unless I'm forgetting
someone.

And how does one explain the survival of tyrannosaurids when most of
the other large groups go into decline in Asiamerica at the end of the
Jurassic?  (OK, so ankylosaurs survived.)

Hmmmm.  Sure wish there were some theropod experts on this list (hint
hint) ....

==
Larry
"Language is a virus from outer space."
http://members.tripod.com/~megalania/index.html



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