CROCODILES

Crocodile (reptile), common name for any of a number of reptiles in a family of the crocodilian order. The term crocodilian refers to all members of the order, which includes alligators, caimans, and gavials as well as crocodiles.



Nile Crocodile One of the largest reptiles on the earth today, the crocodile is also one of the most ferocious. It swallows many small animals whole but will also attack humans and other large animals, often batting them with its tail into a nearby pool of water to make them easier to capture. Crocodiles can close off their nasal passages in the water, allowing them to seize food without drowning. They are immensely strong and may dismember larger prey by simply twisting it to death in the water. The crocodile of the Nile, Crocodilus niloticus, pictured here, is one of the best known of the 12 species of crocodile.Oxford Scientific Films/Stan Osolinski
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Crocodilian Skulls The crocodilians are a group of amphibious, armored reptiles including the crocodiles, alligators, caimans, and the gavial. The shape of the skull is one feature that serves to separate the four groups of crocodilians. In crocodiles (far left) the snout is long and tapered. The alligator skull (next) is distinguished by a more rounded appearance to the snout. The caiman skull is short and broad. The skull of the gavial is easily distinguished from all other crocodilians by the greatly elongated snout and sharp teeth.Dorling Kindersley
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Crocodile Quick Facts Microsoft Corporation. All Rights Reserved.
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II CROCODILIANS

Crocodilians first appeared about 200 million years ago and are believed to be remnants of the great age of reptiles. Their ancestors originally lived on land and were lightly built, but they soon diversified into water-dwelling, or aquatic, and amphibious forms. Except for the alligators, crocodilians live in tropical and subtropical areas of the world. Modern crocodilians are amphibious, spending much of their time in water, where they swim with rhythmic strokes of the tail. The tail is sometimes used to capture prey, sweeping it from shallow to deeper water, where it can be devoured more easily.

Crocodilians are well-adapted as predators, with few natural enemies. Bony plates, called osteoderms, form a kind of armor in their thick skin. Their teeth, about 30 to 40 in each jaw, are set into sockets in the jawbones and interlock when the mouth is closed. In crocodiles, the fourth tooth on each side of the lower jaw protrudes when the mouth is closed; in alligators, these teeth are not visible. The jaws of crocodilians are powerful enough in closing to crush the bones of small animals, but so weak in opening that they can be held together by hand. As the crocodilian floats almost completely submerged, its protruding nostrils and eyes and a portion of its back are the only parts visible as it stalks its prey. Crocodilians are the most vocal reptiles, producing sounds from quiet hisses to fearsome roars and bellows, usually during the mating season. On land, crocodilians move quickly in a belly crawl but can also gallop and walk mammal-like on all four legs.

Crocodiles are physiologically the most advanced reptiles; their internal anatomy resembles that of birds. They have a four-chambered heart and well-developed senses. Cold-blooded like all reptiles—their body temperature depends on the environment—crocodilians bury themselves in mud to estivate or hibernate. In warm regions they are dormant during droughts; in colder regions, during winter.

Crocodilians are egg-laying, or oviparous, reptiles, reaching reproductive maturity at about the age of ten. The eggs, 20 to 90 in number and about the size of goose eggs, are buried in sand, mud, or vegetable debris, where they are left to hatch by the heat of the sun or of vegetable decomposition. Females of some species remain in the area to protect the nest and care for the newly hatched young, although many of the eggs and young are lost to predators. The parental behavior of crocodilians is unique among reptiles and points to their affinity with birds.

III THE CROCODILE

Some members of the crocodile family are the largest living reptiles. Crocodiles usually can be recognized by their long triangular snouts, intermediate between the long, narrow snouts of gavials and the short, oval snouts of alligators and caimans. The Indo-Pacific, or saltwater, crocodile, possibly the largest living reptile, is known to grow to a length of about 7 m (about 23 ft) and to weigh more than 1000 kg (more than 2000 lbs); there are unconfirmed reports of individuals up to 9 m (up to 30 ft) in length. This species inhabits the coastal waters of India, southern China, and Malaysia. A smaller species, the swamp crocodile, or mugger, is found in inland waters of India. The Nile crocodile of Africa was revered by certain ancient Egyptian sects, and mummies of crocodiles have been discovered in Egyptian tombs. In modern times this species has been hunted so extensively that few individuals remain in the lower Nile, but they are still abundant in the upper Nile and southward in Africa to the Cape of Good Hope. In the Americas there are four species of crocodiles. The Cuban crocodile, which has a relatively short snout and reaches about 3.5 m (about 11.5 ft) in length, is restricted to Cuba and the Isla de la Juventud. Morelet's crocodile, comparable in size to the Cuban crocodile, occurs along the Gulf Coastal Plain and Yucatán Peninsula of southern Mexico, Belize, and Northern Guatemala. The Orinoco crocodile inhabits drainages of the Orinoco River system and grows to about 6 m (about 20 ft). The American crocodile, the largest crocodile in the Americas, reaches lengths of about 7 m (about 23 ft) and inhabits a broad range from southern Florida southward, including Cuba and other Caribbean islands, southern Mexico, Central America, and northern South America.

Crocodile eggs are used for food in some parts of the world. The skin is highly valued for leather, and the extract from the musk glands is used in the manufacture of perfumes. Due to overhunting, most crocodiles—including the American crocodile—are considered endangered species.

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Scientific classification: Crocodiles belong to the genera Crocodylus,Osteolamus, and Tomistoma of the family Crocodylidae, order Crocodylia. The Indo-Pacific crocodile is classified as Crocodylus porosus, the swamp crocodile as Crocodylus palustris, the Nile crocodile as Crocodylus niloticus, the Cuban crocodile as Crocodylus rhombifer, the Morelet's crocodile as Crocodylus moreletii, the Orinoco crocodile as Crocodylus intermedius, and the American crocodile as Crocodylus acutus.