[gleeaikin]

After the asteroid crash 65 or 66 million years ago, also known as K-T boundry there must have been one huge ozone hole. The creatures that survived generally were small, probably lived in dens (like mammals), under embankments, (crocodiles), in trees and underbrush, like birds, or had protective shells like turtles, or feathers like birds. Thus they did not die of severe sunburn as probably did those big and small dinosaurs that had skin.

[BlueDragon]

Some made it through, quite possibly in the ways which you have outlined. My own previous comment was something amiss, having spoken too casually while this particular boundary layer was under discussion.

In other more primitive mass die-offs the geological record indicates newly formed (life-form) structural patterns above those other layers differing significantly enough than from fossils below to indicate changes beyond within previously existing life structures/body plan/frames.

Or so we've been told by the likes of mr. Gould, if memory serves.