Re: Hanson 2006, Mortimer, Baeker response

["T. Michael Keesey" <keesey@gmail.com>]

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