[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

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 
_Science_ issue).
        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.