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Re: Brontosaurus/Apatosaurus

In a message dated 98-06-12 14:28:58 EDT, twilliams@canr1.cag.uconn.edu

<< 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_.