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In a message dated 98-06-12 14:28:58 EDT, email@example.com
<< Something which bugs me is that the holotype of _Apatosaurus_ is
actually an immature specimen - in fact, the characters which Marsh
originally used to differentiate _Apatosaurus_ from _Brontosaurus_
(such as lower no. of sacral vertebrae) are juvenile characters.>>
The type skeleton of _A. ajax_ is indeed from a subadult animal--and it is
distinctly larger than the type skeleton of _A. excelsus_, which seems to be
from a fully adult animal. This is the kind of difference that might justify
species distinction but not necessarily generic distinction.
<< I wonder if the holotype of _Apatosaurus ajax_ has enough characters
to diagnose the genus and/or the species, and distinguish it from _excelsus_.
If not, then _Apatosaurus_ is a nomen dubium, and _Brontosaurus_
would be resurrected. >>
The holotype of _Atlantosaurus montanus_ is non-diagnostic, but the holotype
of _A. ajax_ is, according to Jack McIntosh. He found three distinct and
diagnosable species of _Apatosaurus_: _A. ajax_, _A. excelsus_, and _A.
louisae_. This was before the publication of _A. yahnahpin_.