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At 12:25 AM 7/22/00 -0400, you wrote:
>The original morphological studies of tarbosaurs found >four< different
>species in >three< different genera, which were later lumped into one
>and still later unlumped into two species in two genera. I have yet to see
>any ontogenetic study of Asiatic tyrannosaurids, so I don't know where you
>got the idea that the smaller ones grade into the larger ones
Sometimes many species are named because there is a rush to produce
findings (eg, Cope & Marsh). They put out a large number of names for
sauropods. Many were synonymized. Some have also since beein re-split.
Much of it boils down to personal preference (or so it seems). Does it
make sense to create many species of very similar dinosaurs in one area
based mostly on size?
>I wonder how reliable these various "accepted signs of ontogeny" really are.
These things become accepted because there are either A) morphological
changes that occur in many animals (striated bone) or B) grades of animals
that run from smaller specimens to larger ones in a, basically, orderly
fasion. This has been seen with studies on Gorgosaurus (Carr 1999) and T.
bataar (Rozhdestevensky 1965). When you have two specimens that are very
similar to each other (no two are ever the same) and are different from two
bigger specimens in the same way AND you have another specimen that is a
bit bigger than the smaller ones, but smaller than the biggest specimens,
does it not make sense to say they are three stages of the same animal
rather than three separate animals? (Oh my God, that is the largest
sentence I have ever written :-)
Darryl Jones <firstname.lastname@example.org>
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