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Re: mammal mystery
Here's an interesting thought that occurred to me some time back. Does it not
seem likely that at least *once* during the long course of the Mesozoic,
there might have been a localised exception to the "dominance" of dinosaurs
in terrestrial ecosystems. It would seem that all that's needed is a chain of
volcanic islands, a Galapagos or Hawaii. It seems highly unlikely that
non-avian dinosaurs would have ever reached such remote loacles, since they,
like large land mammals, would have been ill-suited for sea crossing.
What *would* be expected would be arrival of most of the groups we see
populating new islands today: various groups of reptiles, avian dinosaurs,
insects, arachnids, amphibians, and small *mammals*. In an enviroment devoid
of comepetion with dinosaurs, perhaps there were a few exceptions, and from
time to time isolated, mammal dominated ecosystems arose.
Of course, now that I think about it, both the Galapagos and the Hawiian
islands failed to produce such a scenario, with reptiles and birds filling in
some niches and others simply remaining unfilled. Hhhhmmm.
Anyway, regarding extinction: we should really avoid words like "failure" and
"success," I think. But Gould and others have already said this time and
again. Extinction is inevitable, like the death of an individual. It's just
what happens, sooner or later. How long does a lineage have to survive to be
judged "successful" by human standards? Any answer would have to be arbitrary
(And so of course we could talk about "more successful" and "less
successful," but since nature isn't keeping score, why should we?).
Caitlin R. Kiernan