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Re: Response to Nick Pharris: Patterns
From: Thomas_R_HOLTZ@umail.umd.edu (th81)
> While this is likely, it is not certain. _Purrusaurus_, an
> alligatorid as large or larger than any of the Cretaceous crocs, is
> from the Miocene of Amazonia, where the largest prey items were 3 m
> long fish, ...
And among the survivors of the K-T transition in the Hell Creek
area were some of the largest freshwater fish in existance -
fish whose descendents can still be found in the Missouri-Mississippi
river system: sturgeon, pike, bowfin (I mean Amia). I rather think
even fairly large crocs could manage on sturgeon.
> Which was long extinct at the K-T boundary. Why would a _Troodon_
> or a small hypsilophodont nest be so hard to conceal? Surely one of
> these little guys could hide under the brush.
And very likely did so.
> Also, as stated before, there is no evidence that Mesozoic birds were
I would venture many were island and/or wetland nesters, however.
> Actually, some Mesozoic mammals DID have to consider this, since
> some (the ancestors of monotremes, and possibly all taxa up to the
> metathere-euthere divergence) were egg layers.
Probably including the abundant and diverse Multituberculates, which
survived quite well until the Eocene.
> Not directly, actually. There is abundant evidence that extinctions
> are correlated with times of climate (and thus habitat) fluctuation.
> In the case of modern extinctions, however, the ultrapredation of
> humans does seem to be a major factor.
Not in all of them. Stephen Gould has written about one (obscure)
recent extinction that was apparently unrelated to human activity.
It was exacly as you say - it was due to environmental fluctuation.
In particular a run of unusual weather in the are where this snail
lived eliminated its narrow habitat temporarily. Bing - its gone.
No predation involved. This mode of extinction is probably a major
one in the absence of oddities like humans.
The peace of God be with you.