Crocodiles, alligators, caimans, and gharials--the Crocodylia, known collectively as crocodylians (or crocodilians)--are the world's largest living reptiles. The largest of them, probably the estuarine or saltwater crocodile, Crocodylus porosus, can grow to almost twenty feet and weigh more than two thousand pounds. Crocodylians are creatures of great contrast. They can remain patiently still for ages, yet can also move like lightning to...