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Re: Brontosaurus compromise



Ken Kinman wrote:

    Well, for those of you who really want to use the name Brontosaurus,
you certainly could use it as a subgenus:  Apatosaurus (Brontosaurus)
excelsus.
    A big name for a big dinosaur.  It doesn't go as far as Bakker might
like, but it's better than no Brontosaurus at all.


Unfortunately, I think we'll have to get used to the demise of the name _Brontosaurus_. The type species of _Brontosaurus_ (_B. excelsus_) is very similar to the type species of _Apatosaurus_ (_A. ajax_). In fact, rather than splitting the two into separate genera (or subgenera -usually not done for fossil vertebrates), it is more likely that the two would be combined into a single species. As Jack McIntosh has pointed out on many an occasion, the two species are indistinguishable based upon the described material - apart from the fact that _A. ajax_ is bigger than _A. excelsus_. (There is some very large _A. excelsus_ material that may invalidate this.) _A. ajax_ also lived later in time.

Bakker (1998) argues that the genus _Brontosaurus_ should not be
sunk into _Apatosaurus_. He bases this principally on a new skull which he refers to _B. excelsus_; it shows a few substantial differences compared to the skull referred to _A. ajax_. However, this skull has yet to be described, and the reasoning behind its referral to _A. excelsus_ has never been published by Bakker (AFAIK).


_A. louisae_, on the other hand, is a good species and is readily distinguishable from _A. ajax_ and _A. excelsus_.


Tim


References

Bakker, R. T. (1998). Dinosaur Mid-Life Crisis: The Jurassic-Cretaceous
Transition in Wyoming and Colorado," in Lucas, Kirkland, and Estep, J. W., eds. pp.67-77.


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