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Re: The uses of sickle claws

At 08:06 AM 9/19/97 -0500, Michael wrote:

>So what's the niche of those predators surrounding T rex?  Were they 
>the hyena of their day?  Did T rex serve as the lion of the day?

Be careful when identifying niches in different environments: they are not
always duplicated from place to place or time to time.  After all, what is
the "lion" of modern southeast Asia?  The tiger is another (very closely
related) big cat, but is a more solitary animal.

Also, to which hyena do you refer?  The brown or striped, which are
relatively small?  The spotted hyena, which is a powerful pack hunter (and
occasional scavenger)?

Although it would be lovely to be able to do the kind of behavioral studies
that are done on modern (primarily sub-Saharan African) predators, but
dino-ethologists are limited to skeletal material, footprint and taphonomic
evidence, and more distant inferences.  (Even being a modern animal doesn't
make a species well understood.  Spotted hyenas still suffer from the
"stigma" of being 'scavengers', even though they are powerful active
hunters, and some populations actually have a higher prey/carrion ratio in
their diet than local populations of lions!).

Which is not to say that we can't make some inferences about predatory
techniques in extinct forms.  However, we have to be aware that we have at
best inferences, not direct observations.  Don't expect to learn "The
Answer", because barring direct field observations, we probably aren't going
to get it.

On the other hand, we can work out some skeletal and biological correlates
of particular predatory techniques to some degree, based on biomechanics and
morphometrics.  In many way, tyrannosaurids are built more like
theropod-hyenas or theropod-wolves: long slender legs, big powerful torsion
resisting skulls with massive teeth, claws with relatively lower angles of
curvature and thicker cross-sections.  Dromaeosaurids are more cat-like:
shorter and more massive legs, tails with specializations for dynamic
stabilization, claws with very high angles of curvature and very narrow,
blade-like cross-sections.

So, if anything, _Tyrannosaurus_ was the hyena of its day, but the "hyena"
was one hundred or more times as massive as the contemporary "lion".

Or, the short form: the Hell Creek fauna was not the Serengeti fauna.

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