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Re: T-J Extinction event article (more media errors?)




George,
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.
------Ken
********************************************************
From: "T. Mike Keesey" <tmk@dinosauricon.com>
Reply-To: tmk@dinosauricon.com
To: <Dinogeorge@aol.com>
CC: <dinosaur@usc.edu>
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, david.marjanovic@gmx.at writes:
>
> << > But as far as cladistically restricting Mammalia to the crown group
>
> I don't advocate that, for the reasons you mention. >>
>
> It seems to me that the most reasonable clade that could be given the name
> Mammalia would be the clade of all amniotes more closely related to extant
> 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.

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