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Re: _Eomaia_ and dung-eating vultures...
----- Original Message -----
Sent: Sunday, April 28, 2002 12:18 AM
> > Just how can one tell that a mammal fossil is placental or not?
One thing is certain -- that *Eomaia* did not reproduce like living
placentals: It retains epipubes ("marsupial bones" -- actually a
synapomorphy of something like mammals in general), and its pelvic outlet is
very narrow. Therefore it is assumed that it behaved like a pouchless
marsupial in this respect (there are some alive), and that this is the
plesiomorphy for live-bearing mammals.
> [...] I believe Placentalia now officially refers
> to crown-group Eutheria.
True. The sister group of Eutheria is Metatheria, whose crown-group is
Marsupialia. (Another definition for Marsupialia, just to confuse everyone,
is stem-based: everything closer to the crown-group than to the
deltatheriids or *Holoclemensia*. Would make all Cenozoic metatherians, and
all North American LK ones AFAIK, marsupials, which many of them are not
under the crown-group definition.)