Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!tdatirv!sarima
From: sarima@tdatirv.UUCP (Stanley Friesen)
Newsgroups: sci.bio
Subject: Re: What's a monotreme?
Keywords: monotremes
Message-ID: <216@tdatirv.UUCP>
Date: 26 Apr 91 20:29:11 GMT
References: <1991Apr22.111159.29888@kuhub.cc.ukans.edu> <4896@kitty.UUCP> <209@tdatirv.UUCP> <416@smds.UUCP>
Reply-To: sarima@tdatirv.UUCP (Stanley Friesen)
Organization: Teradata Corp., Irvine
Lines: 21

In article <416@smds.UUCP> rh@smds.UUCP (Richard Harter) writes:
>In article <209@tdatirv.UUCP>, sarima@tdatirv.UUCP (Stanley Friesen) writes:
>Bones.  They have mammalian jaws.  The inimitable Dr. Asimov argues in one
>of his columns that the fusion of the relevant bones in Platypus is not
>completed until after birth and the correct classification of Platypus
>is a Therapsid and not a mammal at all.

Oops, I forgot that one!! (real silly of me given my paleontology background).

I think Dr Asimov's reasoning is a little off.  The way most paleontologists
define mammals (in practice) is based on the *adult* jaw joint.  That is
any fossil that has a mammal type jaw joint is considered a mammal, and since
most (all?) known fossils of these groups are of adults, that is the deciding
stage of growth.

Of course, if the switch to the secondary jaw articulation is delayed until
after birth, this is just one more indication of how very *primitive* the
monotremes are.
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uunet!tdatirv!sarima				(Stanley Friesen)