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Re: T-J Extinction event article (more media errors?)
I have to agree with the cladists on this one. Such a broad Mammalia
would be even worse than a crown group Mammalia. The vast majority of
pelycosaurs and therapsids were hairless, mammary-less (is that a word?),
and did not have the mammalian jaw articulation/three ear ossicles. The
latter osteological characteristics, although somewhat arbitrary and
imprecise, are the traditional way to separate mammals from their ancestors,
and given the poor monotreme fossil record, such a character-based Mammalia
will continue to be recognized by most mammalogists.
Therefore I recogize at least three mammal orders that are basal to the
crown clade: Sinoconodontiformes, Morganucodontiformes, and
Docodontiformes. And depending on where the monotremes actually split off,
Triconodontiformes and Multituberculiformes may also be basal to the crown
clade, but this continues to be the subject of a lot of controversy.
From: "T. Mike Keesey" <email@example.com>
Subject: Re: T-J Extinction event article (more media errors?)
Date: Sat, 12 May 2001 15:53:48 -0400 (EDT)
On Sat, 12 May 2001 Dinogeorge@aol.com wrote:
> In a message dated 5/12/01 5:40:27 AM EST, firstname.lastname@example.org
> << > But as far as cladistically restricting Mammalia to the crown
> I don't advocate that, for the reasons you mention. >>
> It seems to me that the most reasonable clade that could be given the
> Mammalia would be the clade of all amniotes more closely related to
> crown-group mammals than to the next closest (i.e., the other) amniote
> crown-group, which would be "reptilia+aves."
Don't hold your breath for people to call _Dimetrodon_ a mammal.
Why is this more reasonable than limiting it to the crown clade? I don't
understand that point.
T. MICHAEL KEESEY
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