Re: "No Bolides!"

["Nicholas R. Longrich" <longrich@phoenix.Princeton.EDU>]

        Minor stuff about climate change:
        The argument seems to be that major changes in the temperature 
of the environment could directly impact the dinosaurs, and I don't think 
that's justifiable if we accept dinosaurs as warm-bloods. (which I'd say 
that critters like Cryolophosaurus and the Australia big-eyed 
hypsilophodonts argue pretty strongly for). Warm-bloods don't really have 
that much of a problem coping with temperature changes. What warm-bloods 
have done is change from being tied down by temperature to being tied 
down by food as a limiting factor (well, that's one very general way to 
look at it). Dinosaurs won't die when it gets cold, they'll die, however, 
if food runs out. If the climate changes cause big changes in food 
availability, that can do it, but it probably wouldn't be enough to wipe 
out the dinos directly. 
        Which is also why polar dinosaurs argue so strongly for 
warm-bloodedness. Big ectotherms like Megalania, Geochelone, pythons, 
etc. are tropical and subtropical animals; while coldbloods are mostly 
absent from the poles. It's endotherms like penguins, arctic foxes, polar 
bears, musk oxen etc. that can survive where it's cold. And while the 
Cretaceous did not get as cold as our modern Ice-Age times, it certainly 
seems to have been too cold for ectotherms at the poles. As long as it 
can get the food to keep its metabolism going and it has sufficient 
insulation, a jay or fox can survive sixty below in the Alaskan Interior.
        -nick L.