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Re: Declining pterosaur diversity



On Mon, 29 Nov 2004 18:34:00 -0800 (PST), Jaime A. Headden
<qilongia@yahoo.com> wrote:
> 
>   Okay, first, there don't appear to be that many fossil representatives
> of any mammal crown groups, and only some questionable avian crown groups
> have been identified, including an undescribed "loon," etc.

It seems to me that what's really important here is not crown clades,
but what would have been crown clades during the Paleocene (in other
words, node-based clades specified by specifiers that were alive after
the K/T boundary, as opposed to currently extant). The point may be
confused since there is actually strikingly not much difference.
Correct me if I'm wrong, but, with the exception of some
choristoderans, there wasn't any tetrapod in the Paleocene that did
not fall under crown clade _Monotremata_, _Marsupialia_,
_Placentalia_, _Aves_ (=_Neornithes_), _Crocodylia_, _Lepidosauria_,
_Testudines_, or _Amphibia_ (=_Lissamphibia_), was there? (And could
any of these be divided further?)
Interesting phenomenon....