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Re: _T. rex_ strikes ( was Ceratopsian frills)



At 11:52 AM 12/19/96 -0500, Steve Throop wrote:

>I use _T rex_ as an example of an impact hunter because I don't have
>pictures and data for other tyrannosaurs. I think it was other
>tyrannosaurs, who appeared earlier, that specialized in sauropods.
>
>In the Jurassic, I understand there were a lot of sauropods and
>stegosaurs, long-necked animals who could have eaten tree leaves and
>used their tails to strike predators.  The stegosaurs and most sauropods
>disappeared about the time tyrannosaurs appeared.  

Well, the stegosaurs survived for 30 or so million more years into the
Cretaceous, and sauropods survived until the end of the Cretaceous in many
parts of the world.

Tyrannosaurid diversity, as currently known, is highest where sauropods are
absent.  Although one could argue a cause and effect, you'd have to explain
what Gorgosaurus and Albertosaurus and Daspletosaurus were feeding on after
they offed the yet-to-be-found Judithian and Edmontonian sauropods...

(The more common explanation is that these tyrannosaurids were eating
ornithischians, which were embarrasingly common at the same time and place).

However, some tyrannosaurids lived in the same time and place as sauropods.
Early tyrannosauroids, like Siamotyrannus, occur with sauropods, as do later
Asian forms (Tyrannosaurus bataar).  The southern end of T. rex's range
includes localities from which the titanosaurid Alamosaurus are known, but
it is not established if the latter ever made it into the nothern part of
the range.

>I understand most surviving sauropod species were related to
>_Brachiosaurus_, whose neck was a startling 6 meters off the ground.

Indeed.  One of the middle-range necks of a sauropod: it's longer than in
camarasaurids or dicraeosaurids, but nothing like the really long necked
forms: euhelopodids and diplodocids!

Thomas R. Holtz, Jr.
Vertebrate Paleontologist     Webpage: http://www.geol.umd.edu
Dept. of Geology              Email:th81@umail.umd.edu
University of Maryland        Phone:301-405-4084
College Park, MD  20742       Fax:  301-314-9661

"To trace that life in its manifold changes through past ages to the present
is a ... difficult task, but one from which modern science does not shrink.
In this wide field, every earnest effort will meet with some degree of
success; every year will add new and important facts; and every generation
will bring to light some law, in accordance with which ancient life has been
changed into life as we see it around us to-day."
        --O.C. Marsh, Vice Presidential Address, AAAS, August 30, 1877