Re: Platypus a living fossil?

[Tom Holtz <tholtz@geochange.er.usgs.gov>]

>Surely this is simply a statement of one hypothesis, the other being that
>Mammalia=the common ancestor of all groups traditionally regarded  as
>mammals  EXCEPT Monotremata, the issue being whether including Monotremata
>would perforce include certain creatures that would otherwise be regarded as
>Therapsids (if, for example, the common ancestor were something like
>Diarthrognathus.

I have not seen any (paleo- or neontological) systematics work which
excludes monotremes from Mammalia.  If you have the ref, I'd be glad to
take a look!

(And, the group of marsupials + placentals is almost always called Theria).

                                
                 Thomas R. Holtz, Jr.                  Phone: 703-648-5280      
                 Vertebrate Paleontologist         Fax:    703-648-5420
tholtz@geochange.er.usgs.gov ------------>       th81@umail.umd.edu
U.S. Geological Survey          ------------->       University of Maryland
Branch of Paleontology & Stratigraphy ---->       Department of Geology
MS 970 National Center
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