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T. rex growth, version 2.0


Here's the other shoe dropping on T. rex growth studies:

Horner, J.R. & K. Padian. 2004. Age and growth dynamics of Tyrannosaurus
rex. Proceedings: Biological Sciences 271: 1875-1880.

Tyrannosaurus rex is the most commonly found North American latest
Cretaceous theropod, but until the 1980s only five specimens had been
discovered, and no more than six have received a full description.
Consequently there has been little information on how old Tyrannosaurus
specimens were at maturity or death. Histological analysis of seven
individuals provided, for the first time, an opportunity to assess the
age represented by the bone cortex, to estimate the average individual
age of these skeletons, to determine whether they represented fully
grown individuals, and to predict their individual longevity. Though a
range of ages (15-25 years) was found for the specimens studied, the
seven individuals demonstrate that T. rex reached effectively full size
in less than 20 years. The growth rate of T. rex was comparable to that
of the African elephant, which has a similar mass and time to maturity.
Some of the known specimens of T. rex did not quite reach full size;
others do not seem to have survived long after achieving it.

Unlike the Erickson et al. 2004 paper of a couple weeks ago, this uses MOR
(and ONLY MOR) specimens, and a different technique. Nevertheless, they
reach very similar results: fully adult size at somewhat less than 20 years
old, and the oldest specimens only 25+/- a few years old.  Something
interesting, however, was the variability of sizes: the largest and most
robust were not always the oldest individuals.

                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