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Re: Troodon and other problems (was Andrew McDonald response re: European iguanodonts)
On 4 April 2011 23:13, <GSP1954@aol.com> wrote:
> A problem with using the type of D. carnegie as a neotype for Diplodocus is
> that it is from much higher in the Morrison than the type of D. longus, and
> the latter may be a very different kind of beast -- what we think of as
> Diplodocus may not be present in the lower Morrison.
... except that no-one has ever made a case that D. carnegii is not
the same thing as D. longus. Hatcher's (1901) differential diagnosis,
such as it was, hinged on the backwards slope of the caudal neural
spines, something since shown to be very variable. I don't know the
history in as much detail as I probably should, but it certainly looks
very much as though Hatcher named a new species for his specimen not
because of any taxonomic conviction but because because it was
expected by his sponsor.
Diplodocus is certainly looong overdue for a comprehensive survey and
revision -- something along the lines of what Upchurch et al. (2005)
did for Apatosaurus.
> Dropping poorly defined Apatosaurus in favor of Brontosaurus which is
> founded on the pretty complete Yale skeleton has long been a good idea.
The Apatosaurus material is pretty good -- there are a couple of nice
cervicals. It's not AS good as the Brontosaurus holotype, but it's
plenty diagnostic enough to be getting on with. (Also the
Brontosaurus skeleton is less useful for diagnosis that we might wish,
because the bones are smothered in plaster. They did a really
horrible job on it back in the day -- not just filling in the gaps,
but also in many places smearing over what bone they did have, so it's
impossible to tell what's real and what isn't.)