Title: Crocodile Content: A crocodile is a large amphibious reptile. It lives mostly in large tropical rivers, where it is an ambush predator. One species, the Australian saltie, also travels in coastal salt water. In very dry climates, crocodiles may aestivate and sleep out the dry season. The modern type of crocodile appeared first in the Eocene period. Its ancestors go much further back to the Upper Triassic. The name "crocodile" is also used for any member of the order Crocodilia. They are basically Archosaurs, a group which also includes the dinosaurs. There are many species of crocodiles including the American, slender-snouted and Orinoco crocodile. The crocodile can quickly snap its jaw shut with much power. However, crocodiles have little strength when opening their jaws, such that a person can hold the jaw shut with their hands. Crocodiles range in size from African dwarf crocodiles that measure rarely over 5 feet (1.5 m) to saltwater crocodiles which can approach 23 feet (7 m). thumb|right|250px|Distribution of crocodiles == Description == Crocodiles live in rivers, lakes and dams in parts of America, Asia, Africa and Australia. Some of the crocodiles from Australia live in salt water. These saltwater crocodiles are normally bigger than the ones that live in fresh water. While crocodiles spend most of their time in water, they can come out and move around on the land. Crocodiles cannot breathe underwater: they breathe air. This is usual for land animals which take to the water later in their evolution. When they are not active, they can hold their breath for a maximum of about two hours underwater before drowning. Normally, when underwater, they are active and can hold their breath for a maximum of 20 minutes to one hour. == Behavior == === Feeding === Crocodiles in East Africa take their chances when herds migrate in search of food. To make their annual journey up the East coast, herbivores have to cross rivers. The crocodile looks like it is a log, and hides beneath the surface of the water. When an animal comes down to the water to drink, the crocodile lunges out of the water, grabs the animal in its jaws, and pulls it underwater, where it drowns. The crocodile grab a piece of meat in its jaws and tears it off with a spin-around. Adult crocodiles can go long periods without eating. When crocodiles are very young, they mainly eat insects, crustaceans, snails, small fish, frogs and tadpoles. == What they look like == left|thumb|200x200px|Mugger crocodile Their colors range from brown to grey or greenish-brown. Crocodile tongues are not free. They are held in place by a membrane that can not move. Crocodiles are unable to stick out their tongues. == Alligators and crocodiles == Although there is not much difference in their life-style, biologists put alligators in a separate family. Gharials are also in a separate family, and Caimans are a sub-family of alligators. An obvious difference between an alligator and a crocodile is that one can not see the fourth tooth in the lower jaw of an alligator when the alligator's mouth is closed. The fourth tooth in the lower jaw of a crocodile sticks out when its mouth is closed. == Ancient crocodiles == Some ancient crocodiles walked on two legs like dinosaurs. The scientists found preserved footprints in South Korea. They found hind foot prints but no front foot prints or marks from a tail dragging behind. They were able to tell that these ancient crocodiles walked on their hind legs with their front legs and tails off the ground. They used the whole foot, the way a human or bear does, not just the toes, the way a dinosaur, bird or dog does. ==Species== The order Crocodilia has 27 living species in nine genera. This does not include hybrid species or extinct prehistoric species. Modern molecular studies indicate that the nine genera can be grouped into three families. Family Alligatoridae (Alligators and caimans) *Genus Alligator: two species *Genus Caiman: three species *Genus Melanosuchus: one species *Genus Paleosuchus: two species Family Crocodylidae ("True" crocodiles) *Genus Crocodylus: fourteen species *Genus Mecistops: two species *Genus Osteolaemus: one species Family Gavialidae (Gharial and false gharial) *Genus Gavialis: one species *Genus Tomistoma: one species