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Re: (extinction)




On Tuesday, July 2, 2002, at 09:33 AM, David Marjanovic wrote:
Crocs live.

Not all. Baurusuchidae snuffed it, unlike the closely related Sebecidae. The
specialized turtle-eater *Brachychampsa* went with it. All that diverse
Notosuchia stuff is gone, though nobody knows if right after the late
Maastrichtian or later.
It is expected that generalized crocs survive such an event. They
aren't dependent on "green food chains", they can eat carrion and fast for
months.
Any comments from the croc experts? What old blunders in croc
systematics have I repeated? :-)

There's the weird bulldog faced croc from Madagascar. Given that its teeth were mistaken for herbivorous dinosaur teeth, that its got a little pinhead on a big body, and a ventrally displaced jaw joint which contributes to a shearing motion of the jaws, I'd bet money or a case of good beer that this is a herbivore. Like the other large land herbivores in the end Cretaceous, tho, it bit it. This (and conversely the survival of the champsosaurs which aren't crocs but which are like the aquatic crocs in ecology) argues that it was not anything particular about the dinosaurs themselves, but rather, where they sat in the ecological web, that determined who did and who didn't survive. We need to stop asking "why did the dinosaurs die out" since so much besides dinosaurs did die out, and start asking "why did the large (greater than a meter or two) land carnivores and herbivores die out?" Calling this a "dinosaur extinction" is misleading, more accurate but rather less wieldy would be to call it a "large terrestrial animal and marine stuff extinction".
There were also some really big land turtles in the Late Cretaceous, something like a meter in diameter though they aren't big and domed. I don't know if they extended into the Maastrichtian but if the breakdown of the terrestrial food chain did occur, one would expect that these things also failed to make it into the Cretaceous so again you're left looking at at this in terms of targeting specific ecologies, not taxa.