Stegosaurs, theropod systematics, time scales

[Tom Holtz <tholtz@geochange.er.usgs.gov>]

>One other point: correct me if I'm wrong (and I know you all will) but
>stegosaurus was from the earliest age of dinosaurs - none of them ever
>_had_ to face down a t-rex.  The carnosaurs of that age were not so
>formidable as the ones that triceratops had to deal with.

Well, you are wrong, but not entirely.  Stegosaurus is from the middle of
the age of dinosaurs (the Late Jurassic), Tyrannosaurus from the end (the
Late Cretaceous).  Also, Tyrannosaurus is not a carnosaur, but a
coelurosaur.  And, Carnosauria may not be a valid taxon, with Allosauroidea
being closer to coelurosaurs than to Megalosauroidea.

But you are right - even Saurophagus is somewhat less threatening than
Tyrannosaurus (in the same way a 30 megaton bomb is less threatening than a
40 megaton bomb, I suppose).

Incidentally, with regards to the time scale, more time seperates
Stegosaurus and Tyrannosaurus (145-65=80 million years) than seperates
Tyrannosaurus from us (65-0=65 million years).  The Cretaceous was a LONG
time period.

                                
Thomas R. Holtz, Jr.                                   
tholtz@geochange.er.usgs.gov
Vertebrate Paleontologist in Exile                  Phone:      703-648-5280
U.S. Geological Survey                                FAX:      703-648-5420
Branch of Paleontology & Stratigraphy
MS 970 National Center
Reston, VA  22092
U.S.A.