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Re: Oh no! Not Monotremes again!
>From: jshields@iol.ie (James Shields)
>
> The interesting bit, however, is this:
>
> "Although they resemble reptiles in that they lay eggs, the monotremes are
> true mammals. They possess such distinctively mammalian characteristics such
> as mammary glands, hair, a large brain, and a complete diaphragm."
This is correct. They should also mention milk glands.
>
> And:
>
> "Most authorities beleive that the order Monotrema originated from a line of
> mammal-like reptiles different from that which gave rise to the other
> mammals."
This is now out of date. This seemed to be the case for awhile
in the mid '80's, but has now been shown to be based on incorrect
analysis.
>
> No cladistics here!
Actually, the supposed evience for a seperate origin *was* based
on cladistic analysis - it just wasn't transformed into classification
by many people.
But in fact, if it had turned out to be true, even us non-cladistic
evolutionary taxonomists would have had to seperate the monotremes,
and the other non-therian mammals, from Mammalia, on the grounds that
such a Mammalia would have been *poly*phyletic, which *nobody*
accepts as valid, cladist or not.
[The main argument between cladists and non-cladists is the validity
of *para*phyletic taxa].
swf@elsegundoca.attgis.com sarima@netcom.com
The peace of God be with you.