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Re: Battat's hair; Prototheria



>>Monotreme mommas make milk--how can they
>>not be mammals?
>
>You would have thought that any animal with mammary glands would have to be
>mammals, wouldn't you? However the "official" definition has to do with the
>shape of the jaw (someone posted it recently). I think that the reason milk
>doesn't prove mammalness is that a lot of therapsids appear to have had
>lips, implying that they suckled, implying that they were milk producers. I
>think these are not considered to be mammals because they lack other major
>characteristics of modern mammals.
>
>Perhaps someone who has studied extinct mammals can cast some light on the
>subject.

No, no, no - they ARE considered mammals!!  And are so by the VAST majority
of paleontologists and mammalogists.  Someone posted what may be the only
technical reference from the 20th Century which considers them nonmammalian
therapsids.

The official defintion is either the gradistic one (mainly doing with jaw
articulations, under which montremes *are mammals*) or the cladistic one
(all descendants of the most recent common ancestor of Montremata and
Theria, so they are necessarily mammals!!).

                                
                 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
Reston, VA  22092               ------------->        College Park, MD  20742
                                                          U.S.A.