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croc & champsosaur survival



        I think if you want to know why champsosaurs and crocs make it, you
have to consider things in terms of a marine extinction pattern, a
terrestrial pattern, and a freshwater aquatic pattern. Of the three, the
freshwater aquatic ecosystem is the least impacted; crocs, champsosaurs,
turtles, various groups of fish, frogs, salamanders, etc. all seem to make
it through relatively unscathed (again, relatively: they probably got only
99% wiped out or something like that).
        Of course, one wonders why some dinosaurs could not simply survive
on fish, and plenty of pterosaurs were piscivores. But then, maybe it
wasn't that the aquatic ecosystem survived, so much as it was preadapted
for going through things like asteroid impacts. The aquatic ecosystem
perhaps was torn apart, but it had lots of survivors, and the other ones
didn't. I believe that most of the above animals can just burrow into the
mud for the winter (although if they were adapted for doing so in the
rather mild Mesozoic, I don't know). Amphibians can respire through the
skin, and turtles can respire through the rectum; and since ectotherms use
less oxygen at low temperatures and the water can hold more oxygen, I think
a lot of freshwater creatures can just burrow into the mud and stay down
all winter. As to crocs, they obviously must have done something different.
One advantage may have been a low metabolism, which would have been useful
to prevent starving to death until the hypothesized Asteroid Winter was
over.

        -N