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Re: Platypus a living fossil?



>(Bill Adlam writes):
>>I don't feel Ornithorhynchus qualifies as a living fossil:
>
>The platypus is only a living fossil in so much as some believe
>that it and the Spiny Anteater are the last surviving therapsids
>(Does anyone have an opinion on this?  I always regarded them as
>mammals myself).

The distinction between mammals and therapsids is fairly clearly defined (It
has to do with the shape of the jaw). I'm pretty sure both Platypus and
Spiny Anteaters fall on the mammal side.

Of course, under cladistics all mammals are therapsids.

Anyway, I have two suggestions for the definition of a living fossil.

1. An organism belonging to a group which was once diverse and widespread
but is now limited to a few species.

2. An organism which was discovered in fossil deposits before the living
organism was discovered.

These are just my personal ideas, by the way, but I'd like to know what some
of the experts think.

Under (1) I think both Platypus and Spiny Anteaters would qualify, being the
last of the echidnas. As I understand there is only one species of Platypus
and about half a dozen of Spiny Anteaters (sorry I don't know the scientific
names).

James Shields  -  jshields@iol.ie  -  http://www.iol.ie/~jshields
-------------------------------------------------------------------------------
And when the ark was finished Noah said unto Elvis, "What do you reckin?"
And Elvis checked out his own cabin and shook his head saying "poky".
And so did they knock several walls through and install a jaccuzzi.
And when it was all done Noah scratched his beard and said, "We don't have
room for all the animals now."
And Elvis perused the livestock list and in his wisdom said, "Lose the
dinosaurs."
        -Robert Rankin, The Suburban Book of the Dead