Reptiles are air-breathing vertebrates covered in special skin made up of scales, bony plates, or a combination of both. They include crocodiles, snakes, lizards, turtles, and tor- toises.

The axolotl is a member of a family of newts, salamanders and other amphibians. But instead of switching to lung breathing, it keeps its gills and enters adulthood while it still appears to be a ...