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Re: Hanson 2006, Mortimer, Baeker response

On 6/12/06, Michael Mortimer <mickey_mortimer111@msn.com> wrote:

A couple of minor nitpicks:

In regard to the theme of this thread, finding 'new' categories of dinosaurs
is impossible in a way.  At least in the sense of broad groups like
Sauropoda.  After all, Dinosauria is defined to only include Saurischia and
Ornithischia.  So any dinosaur has to fall into those clades.

Except for the dinosaur ancestor, of course.

Saurischia is
defined to only include Sauropodomorpha and Theropoda, so again, any
saurischian will be one of those.

Almost. _Eusaurischia_ includes nothing but _Sauropodomorpha_, _Theropoda_, and their final common ancestor. But there were also non-eusaurischian saurischians, possibly including _Eoraptor_ and _Herrerasauridae_.

I completely agree with your basic point, though. One has to quantify
what one means by "a new category of dinosaur" (i.e., a new clade with
a ghost lineage of XX million years or some such) before one can
discuss it meaningfully. On its own the statement either includes
every new discovery (every new taxon is a "new category") or none of
them (no new taxon belongs to no preexisting groups--unless it's
genuine alien life, of course).
Mike Keesey
The Dinosauricon: http://dino.lm.com
Parry & Carney: http://parryandcarney.com