Gnatusuchus is an extinct genus of caiman represented by the type species Gnatusuchus pebasensis from the Middle Miocene Pebas Formation of Peru. Gnatusuchus lived about 13 million years ago (Ma) in a large wetland system called the Pebas mega-wetlands that covered over one million square kilometers of what is now the Amazon Basin.

Necrosuchus is an extinct genus of caiman from modern day Argentina that lived during the Paleocene epoch. It inhabited the fluvio-lacustrine environment of the Patagonian Salamanca Formation.