Tell us about the dinosaurs

[Ryft]

In astronomy we were having a lecture on the asteroid that caused extinction and gave rise to the age of the mammals via evolution, and some guy in the class said, "Then why are there reptiles today?"

A very strange question for him to have asked, as the 'dawn of the age of mammals' does not equate to 'extinction of all reptiles'. So there are reptiles today because, obviously, numerous species in that class survived the Cretaceous extinctions (e.g., crocodiles), as did those of other classes. What an odd question.

I quipped that, through natural selection, the colder blooded life forms died out, leaving those with warm blood or a feather covering like raptors to stay warm enough to survive.

I doubt the extinctions had much to do with thermoregulation so much as cascading disruptions in the food chain; i.e., from asteroid impact to catastrophic volcanism to sea level regression, the extinctions in plants and organisms would have repercussions up the food chain to herbivores and predators. The extinctions took place over several hundred millennia, not a singular occurrence from one event; there is a difference between the deaths of countless animals and real species extinction.