Crocodiles are members of the family Crocodylidae, which belongs to the order of crocodilians.

Sometimes, crocodiles are known as true crocodiles, to distinguish them from other crocodilians - alligators, caimans, gharials and false gharials.

Crocodiles live in tropical North, Central and South America, Asia, Africa and Australia.

The largest crocodile in the world is the saltwater crocodile (Crocodylus porosus). The saltwater crocodile is the largest reptile living on Earth today. Male saltwater crocodiles generally grow up to about 17 feet long. Some saltwater crocodiles have grown to be more than 20 feet long. The saltwater crocodile  is also known as the estuarine crocodile.

Saltwater crocodileThe saltwater crocodile is native to India, Southeast Asia and Northern Australia.

The smallest living crocodile on Earth is the dwarf crocodile (Osteolaemus tetraspis), which lives in Africa. It usually grows to about 5 feet long.

Dwarf crocodileCrocodiles have narrow V-shaped snouts. The snout of a crocodile differs from the snout of an alligator, which is wider and U-shaped.

A crocodile's upper and lower jaws are equally wide. When the crocodile closes its mouth, its top and bottom teeth are visible. An alligator's upper jaw is wider than its lower jaw. When an alligator closes its mouth, its bottom teeth are invisible because they fit inside sockets in the upper jaw.

The largest tooth in a crocodile's mouth is the fourth tooth in its lower jaw. The fourth tooth fits into a notch on the outside of the upper jaw.

Crocodiles are predators and eat many different kinds of animals, including insects, crustaceans, fish, birds and mammals. They sometimes eat smaller crocodiles. They can eat very large animals, such as sharks, zebras and water buffaloes.

Sometimes crocodiles will attack and eat human beings.

The Nile crocodile (Crocodylus niloticus), which lives in areas with relatively large human populations, kills about 200 humans every year.

A crocodile hunts by lying in wait for an animal to come by and then ambushing it.

It will hold an animal underground until it drowns.

The crocodile will kill a larger animal by dragging it underwater until it suffocates, then spinning around with it so that chunks of the animal's body become torn off.  This spinning behavior is known as a death roll.

Crocodiles are well adapted for lives as aquatic predators. They have streamlined bodies that allow them to move through the water with little resistance. They can tuck their webbed feet into their sides when they swim. This decreases water resistance even more.

A crocodile can travel very quickly on land, as well as in the water. Some crocodiles can move as fast as 11 miles per hour on land.

Crocodiles lay eggs in nests. They are very protective parents.

The sex of a crocodile embryo is determined by the temperature at which the egg is incubated.

A change in temperature, such as caused by global climate change, could affect the ratio of males to females in a crocodile species. If too many males or too many females were to hatch, the species would lose its ability to reproduce. This would cause the species too become extinct.