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RE: The Final Days
Original Message by Daniel Bensen Saturday, 16. November 2002 06:46
> >> The ending of many lines of avian-dinosaurs at the K-T boundary is
> further evidence that something other than large size and large appetites
> were responsible for extinction. [...]<<
Crocs are ectothermic and can therefore fast on end, more or less. Endotherms
can't do that without special adaptations (e. g. hibernation). And who says
that any adult croc survived, BTW. Maybe the only surviving individuals were
insect-eating babies of 1/10 or less adult length.
> Geography may have played a role, as well. It's starting to look like
> most extant vertebrate groups have their roots in the Southern
> Hemisphere. It makes sense intuitively, though someone will probably
> shoot me down here.
> Where do lungfishes, marsupials, ratites, and tuataras live?
Marsupials probably don't count -- crown group marsupials have, ignoring the
tooth from Madagascar that may or may not belong in there, never occurred
outside South America + Antarctica + Australia, and other metatherians
survived on the northern continents well into the Miocene. There is one case
that is totally counterintuitive -- in the Maastrichtian, gars
(Lepisosteidae) apparently had a pretty worldwide distribution, and
throughout the Cenozoic, they have AFAIK been confined to... North America.
On the whole, though, the picture holds, especially for birds.