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RE: tooth question

At 04:39 PM 1/26/99 -0800, Dwight Stewart wrote:
>Which made me think of another question: Dr. Horner states
>that there is evidence for a fast growth rate in Tyrannosaurus rex up to the
>age of 4-5
>       years (sorry, not sure about the exact number of years) and that
>after the
>       specimen neared or attained adult status, the growth rate altered.
>He states that this implies that the animal may have changed metabolism
>strategy after a
>       certain time/age.  Do you agree and if so, what about other
>       species, such as bataar?  Is their evidence of the same or a similar
>growrth pattern with them?

Well, the evidence seems to be coming in from many dinosaur lineages
(hadrosaurids, troodontids, sauropods, etc.) that a period of fast growth
was followed by a big slow down. (Dryosaurs, for some reason, have different
style bone growth).  The data look pretty good to me.  However, beware of
"ageing" of dinosaur individuals done in the 1980s and early-to-mid 1990s:
as has been shown by recent work by Horner and others, the old "1 LAG = 1
growth year" paradigm doesn't seem to hold, as different bones in the same
individual have different numbers of LAGs!

I have to say that no one, to my knowledge, has published any growth rate
studies for T. rex (the only small T. rex postcranium known is the type of
"A. megagracilis").  Such a study would be feasible for T. bataar or
Gorgosaurus libratus, but at present nobodies done that work.  However,
based on the widespread presence of this pattern among dinosaurs, I wouldn't
be surprised if it held for tyrants as well. 

Thomas R. Holtz, Jr.
Vertebrate Paleontologist     Webpage: http://www.geol.umd.edu
Dept. of Geology              Email:tholtz@geol.umd.edu
University of Maryland        Phone:301-405-4084
College Park, MD  20742       Fax:  301-314-9661