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RE: New Tyrannosaurus paper

> From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of
> Steve Brusatte
> Yes, true.  A good comparison, therefore, would be the French
> ceratosaur (is it still classified as a "ceratosaur"?)
> _Genusaurus,_ which has whopping cnemial crests.  IIRC, there is
> enough material known of _Genusaurus_ to complete a
> Hutchinsonesque study.

I greatly disagree: we have very little knowledge of this animal, and
estimations of its mass (and, for that matter, the lengths of the various
hindlimb elements!) would be so approximate as to be mere speculation.

>  I would be interested to see what the
> estimated speeds of _Genusaurus_ (with its huge cnemial crests)
> were, and how they compared to _Tyrannosaurus_.

Interesting, yes, but one of the basic points coming out of various lines of
research is that the mechanical world that 3 or 4 or 6 or more tonne animals
live in is very different from the world that 100 kg or 500 kg or maybe even
1 tonne animals live in.  (Disappointing, I know; I really didn't want to
believe that for a long time myself...).

> Hopefully, this paper will lead to much similar research
> involving all types of extinct animals.


> From: philidor11 [mailto:philidor11@snet.net]
> Just three questions in advance of finding out more:  have the potential
> prey animals for T. rex been checked with the same sort of models?  If it
> turns out they could escape consistently, that might have implications.

They have not done so yet; however, preliminary evidence would suggest that
the size factors might even hurt the hadrosaurids and ceratopsids worse than

> And finally, an ambush hunter which needs a short sprint would have a
> different build presumably from a chase 'em down hunter.  I
> expect there are
> assumptions about posture and stride built into the calculations; is it
> possible to draw any conclusions about the type of hunting the animal was
> doing?

Unfortunately, we don't have modern terrestrial predators in that size
range, so it is difficult to know what postural differences one should
expect with a 6 tonne mass.  Additionally, changes in the size of the
animals involved and the type of vegetation available may mean that late
Cenozoic terrestrial "ambush" vs. "pursuit" stereotypes do not apply to
Mesozoic multitonne theropods.  However, as shown by my research and others
(Paul, Currie, Christiansen, Carrano), tyrannosaurs have tibiae and
metatarsi which are elongated relative to those of other comparable-sized
predators.  In the modern world, elongated hindlimbs are associated with
pursuit predators more so than ambush predators.

                Thomas R. Holtz, Jr.
                Vertebrate Paleontologist
Department of Geology           Director, Earth, Life & Time Program
University of Maryland          College Park Scholars
                College Park, MD  20742
Phone:  301-405-4084    Email:  tholtz@geol.umd.edu
Fax (Geol):  301-314-9661       Fax (CPS-ELT): 301-405-0796