RE: Tyrannosaur numbers

["Thomas R. Holtz, Jr." <tholtz@geol.umd.edu>]

> From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of
> Benjamin Hughes
>
> Hi all
> I'm relatively new to the DML, certainly no expert like manyof you here, but
> jut thought I'd add my bit. I have ideas and if I'm wrong then I'm happy to
> hear why.
> I have heard (coan't remember source, sorry) that there are very few
> Tyrannosaur fossils ever found. Whether this means that few have been found
> out of a large amount still undiscovered, that few of the animals ever
> happened to be fossilised in the first place, or that there were few
> Tyrannosaurs ever in existance at all, I am not sure.

As a matter of fact, Tyrannosaurus is a relatively common species, as far as 
carnivorous dinosaurs go. The generally unknown
(outside the paleo community) truth is that most dinosaur and other fossil 
animal species are known from less than one individual.
(That is to say, they are known from only one incomplete fossil). Until the 
1990s there were perhaps two dozen T. rex skeletons
(from ~5% to 50% complete), and then during the 1990s the work by various teams 
(BHI, MOR, RTMP, etc.) have uncovered many more.

Others have already pointed out the paper by White et al. showing that T. rex 
appeared to represent about 4% of the total fauna,
which is on a par with other carnivorous dinosaurs from other dinosaurian 
faunas.

> My point is that if it were true that there were few Tyrannosaurs, then this
> would most likely mean that it was simply because they were innefective
> predators, too big and cumbersome to catch faster prey, or to compete with
> slightly smaller predators.

Ummm... what slightly smaller predators?  The next largest definite terrestrial 
carnivorous species in that environment could fit
entirely within the jaws of an adult T. rex...

> Is there any way of knowing without the actual fossils the number of
> Tyrannosaurs that existed?

"Know"?  No, there isn't.  ESTIMATE, yes. The difficulty here is that the 
parameters involved are so difficult to pin down
(metabolic rate, plant productivity, etc.) that you can predict different 
orders of magnitude for the numbers of T. rex that North
America could support at a given time. The primary work along this line is by 
Jim Farlow, with recent additions to this research by
Scott Sampson, Mark Loewen, and Matt Carrano.

                Thomas R. Holtz, Jr.
                Vertebrate Paleontologist
Department of Geology           Director, Earth, Life & Time Program
University of Maryland          College Park Scholars
        Mailing Address:
                Building 237, Room 1117
                College Park, MD  20742

http://www.geol.umd.edu/~tholtz/
http://www.geol.umd.edu/~jmerck/eltsite
Phone:  301-405-4084    Email:  tholtz@geol.umd.edu
Fax (Geol):  301-314-9661       Fax (CPS-ELT): 301-405-0796
>