Complex sentence: They appeared 83.5 million years ago in the Late Cretaceous period, and include true crocodiles (family Crocodylidae), alligators and caimans (family Alligatoridae), and the gharial and false gharial (family Gavialidae).
Split into simpler sentences: They appeared 83.5 million years ago in the Late Cretaceous period. The order includes the true crocodiles (family Crocodylidae), the alligators and caimans (family Alligatoridae), and the gharial and false gharial (family Gavialidae).