But it was as large semi-aquatic preditors that they became most successful. Crocodiles are superbly adapted to life in rivers and swamps. A fold of skin closes the windpipe at the back, so that the animal can open its mouth under water and breathe with its nostrils above the surface. The nostrils, like the eyes and ears, are placed high on the head. When crocodiles are completely submerged, the ears and nostrils are closed by valves, and the eyes covered by membranes.
Crocodiles have no salivary glands and usually eat under water.
Some species sweep their prey from the land into the water with their powerful, vertically flattened tails, a technique that was almost certainly also practiced by Phytosaurs of the late Triassic. The warm balmy Mesozoic climate was kind on these prehistoric reptiles, and they flourished and diversified for many millions of years, attaining world-wide distribution. The larger semi-aquatic types lunched on dinosaurs and large lungfish and Lepidotids. The global cooling trend that began in the Oligocene epoch and accelerated in the Miocene and Pliocene was catastrophic for the crocodiles. Many types died out, unable to cope with the increasing cold, and the survivors retreated to the tropics and a life in swamps.