Eusuchia

Eusuchia ("true crocodiles") is a clade of crocodylimorphs that first appears in the Early Cretaceous period. All living crocodilian species are eusuchians, as are many extinct forms.

Description
Unlike primitive crocodylomorphs, eusuchians possess a secondary bony palate. This feature enables crocodiles and alligators to safely breathe in through their nostrils while the rest of the head (including the mouth) remains submerged.