Some data (was Re: Herbivore protection)

["Thomas R. Holtz, Jr." <th81@umail.umd.edu>]

At 11:38 PM 5/27/97 -0400, Wabandco wrote:
>Actually, the issue we were tossing about (understand, I'm the rank amatuer
>in this discussion, and I'll not be usurped! ;-)) stemmed from a
>disproportionately low fossil representation of T.'s to Hadrosaurs.

Whoever claimed that?

Depending on the method used, the ratio of tyrannosaurids to all
ornithischians (hadrosaurids and ceratopsids, predominantly) range from 1:5
(well within the ectothermic predator:prey ratios) to 1:511 (which would be
very low even for an endothermic predator:prey ratio).  Here are some the
results (taken from Farlow, J.O. 1993.  On the rareness of big, fierce
animals: speculations about the body sizes, population densities, and
geographic ranges of predatory mammals and large carnivorous dinosaurs.
American Journal of Science 293-A:167-199).

(the orignial papers for the data can be found in the text of the article).

1:10-1:13  Judith River Group, based on articulated specimens.
1:5-1:6  Judith River Group, based on surface collected isolated scrap.
1:23  Hell Creek Formation, based on surface collected isolated scrap.
1:22-1:511 (mean 1:115) Judith River Group, based on screen washed samples.

Thus, there does not seem to be a "disproportionately low fossil
representation" of tyrannosaurids at all.

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