The American crocodile (Crocodylus acutus) has a V-shaped head and a pointed snout which distinguishes it from the caiman. It sports a prominent bump between its eyes and nostrils. It differs from other Crocodilians in that the fourth tooth in each of its lower jaws points upwards when its mouth is closed. Very receptive to the infrasound emitted by the vibrations in the water, the American crocodile has specific characteristics: triple eyelids, the obstruction of its nostrils and its ears as well as a secondary palate which isolates its nasal and oral passages in diving, a muscular membrane that separates its respiratory and digestive tracts.