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Re: mammal radiation ONLY after dinosaur extinction
On Mon, 3 Jun 1996, Mickey Rowe wrote:
> The fact that proto-ungulates apparently arose 20 million years before
> the non-avian dinosaurs died out is significant only because their
> descendents later radiated into so many contemporary mammal species.
> The new finds and newly proposed phylogenetic significance of older
> finds are interesting for a lot of reasons, but they do NOT throw into
> question the currently accepted scenario for mammalian evolution --
> that the adaptive radiation that ultimately lead to contemporary
> mammalian diversity was possible only AFTER the ecological release
> brought about by the demise of the dinosaurs.
How do you know which adaptations lead to contemporary mammalian
diversity? This is merely _your_ opinion. One more to my liking is
Blair Hedges' writing in _Nature_ a couple of weeks ago and commenting
on his own molecular evidence and Archibald's fossils: "The existence of
the early ungulates really demonstrates that the evolutionary radiation
of the modern orders of placental mammals was well under way [100
million years ago]." (Also on pp. 1102 of the 24 May
Actually, it was in an evolution class, listening to one of S.J.
Gould's students ranting about the insignificance of pre K/T mammals,
that I first "copped an attitude" about the whole issue. The scenario he
accepted involved only shrew-like insectivores who had lived under the
dinosaurs for a hundred million years. This is no longer "accepted".
What Archibald's evidence should be forcing us to accept is a new idea
involving a robustly evolving group of species radiating into new niches
throughout the late Cretaceous. The real excitement in this find is in
wondering what these niches might have been.