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




David,
I didn't know about the temporal extension of therapsids into the Early Cretaceous. Will have to look into that.
But as far as cladistically restricting Mammalia to the crown group, it has met a lot of resistance. Such a crown group would be anchored on the monotremes, which still have a very dismal fossil record. Therefore I think it is even less acceptable than a crown group Aves, and that idea didn't really go anywhere. And you don't want to get me started on a crown group Reptilia.
McKenna does recognize what he believes to be a crown group Mammalia, but it is controversial whether monotremes or multituberculates split off earlier. Therefore, many mammalogists still prefer a more traditional Mammalia, including sinoconodonts and morganucodonts (both of which survived the Triassic-Jurassic transition).
-----Ken
******************************************************
From: "David Marjanovic" <david.marjanovic@gmx.at>
Reply-To: david.marjanovic@gmx.at
To: "The Dinosaur Mailing List" <dinosaur@usc.edu>
Subject: Re: T-J Extinction event article (more media errors?)
Date: Sat, 12 May 2001 00:53:46 +0200

> > Tritylodontids survived into the EK (in Japan); all other synapsids
besides
> > mammals were indeed gone by the Tr-J mass extinction.
>
> Well ... "besides mammaliforms". There are some taxa that may not belong
> to crown group _Mammalia_ which persisted.

This is another problem -- whether Mammalia has the traditional content
(with *Morganucodon*, *Megazostrodon* etc., without Tritylo- &
Tritheledontidae) or is restricted to the crown group. AFAIK there is no
consensus yet.

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