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Re: Why did only avians survive?



<<What about the idea that only (some) animals under a certain size managed
to survive? Any evidence &/or good arguments for this?>>

I don't know what the crocodile fossils might show, Peter.  However, aside
from that blind spot, support is provided by the lack of big land animals in
the earliest Paleocene fossil record.  The mammals were small and squeaky.
After a few hundred thousand years, dog-sizes came into fashion; both
herbivores and meat-eaters.  Very few earlier versions had been anything
like as large.

The present Cretaceous mammal record holder seems to be Repenomamus from the
Lower K of Liaoning.  A skull manages over 10 centimetres.  However, some
Maastrichtian mammals were probably that sort of size as well: Didelphodon
and Schowalteria.  I've also heard of a centimetre long tooth from
Patagonia, which is apparently Campanian.  It's some kind of dryolestoid
apparently.  Much smaller versions had been popular in the north sixty
million years earlier.