Crocodile, Survived Great Extinction Events.

A crocodile is any species belonging to the family Crocodylidae (sometimes classified instead as the subfamily Crocodylinae). The term can also be used more loosely to include all members of the order Crocodilia: i.e. the true crocodiles, the alligators and caimans (family Alligatoridae) and the gharials (family Gavialidae), or even the Crocodylomorpha which includes prehistoric crocodile relatives and ancestors. Crocodiles are large aquatic reptiles that live throughout the tropics in Africa, Asia, the Americas and Australia. Crocodiles tend to congregate in freshwater habitats like rivers, lakes, wetlands and sometimes in brackish water. They feed mostly on vertebrates like fish, reptiles, and mammals, sometimes on invertebrates like mollusks and crustaceans, depending on species. They are an ancient lineage, and are believed to have changed little since the time of the dinosaurs. They are believed to be 200 million years old whereas dinosaurs became extinct 65 million years ago: crocodiles survived great extinction events.

Age
There is no reliable way of measuring crocodile age, although several techniques are used to derive a reasonable guess. The most common method is to measure lamellar growth rings in bones and teeth - each ring corresponds to a change in growth rate which typically occurs once a year between dry and wet seasons. Bearing these inaccuracies in mind, the oldest crocodilians appear to be the largest species. C. porosus is estimated to live around 70 years on average, and there is limited evidence that some individuals may exceed 100 years. One of the oldest crocodiles recorded died in a zoo in Russia. A male freshwater crocodile at the Australia Zoo is estimated to be 130 years old.

Size
Size greatly varies between species, from the dwarf crocodile to the enormous saltwater crocodile. Species of Palaeosuchus and Osteolaemus grow to an adult size of just 1 to 1.5 m. Larger species can reach over 5m (16 ft) long and weigh well over 1200 kg (2,640 lb). Crocodilians show pronounced sexual dimorphism with males growing much larger and more rapidly than females. Despite their large adult size, crocodiles start their life at around 20 cm (8 inches) long. The largest species of crocodile is the saltwater crocodile, found in northern Australia and throughout south-east Asia.
The largest recorded crocodile is a giant saltwater crocodile measured at 8.6 meters (28.2 feet) and 1352 kg weight (2870 lb) shot in Sumatra, Indonesia in 1978. The largest living crocodile known is a 7.1 m (25.3 ft) long saltwater crocodile, in Orissa, India.

Etymology
The crocodile gets its name from the Greeks who observed them in the River Nile. The Greeks called them krokodilos, a compound word from kroke, which means "pebble" and drilos, which means "worm". To the Greeks, this "worm of the stones" was so named because of the crocodiles habit of basking in the sun on gravel-covered river banks.

Biology and behaviour
Crocodiles are ambush hunters, waiting for fish or land animals to come close, then rushing out to attack. As cold-blooded predators, they are lethargic, therefore survive long periods without food, and rarely need to actively go hunting. Despite their slow appearance, crocodiles are top predators in their environment, and various species have been observed attacking and killing sharks.[8] A famous exception is the Egyptian Plover which is said to enjoy a symbiotic relationship with the crocodile. According to unauthenticated reports, the plover feeds on parasites that infest the crocodile's mouth and the reptile will open its jaws and allow the bird to enter to clean out the mouth (Richford and Mead 2003).
Many large crocodilians swallow stones (called gastroliths or stomach stones) and they are believed to be of use in acting as ballast to balance their body. Other suggestions have been made that they may have a function similar to that of grit in birds, which is in crushing food.
Salt glands are present in the tongues of most crocodylids and they have a pore opening on the surface of the tongue. They appear to be similar to those in marine turtles, however these seems to be absent in Alligatoridae.
Crocodilians can produce sounds during distress and in agressive displays. They can also hear well and the tympanic membranes are concealed by flat flaps that may be raised or lowered by muscles.
Crocodiles eat fish, birds, mammals and occasionally smaller crocodiles.

Danger to humans
The larger species of crocodiles are very dangerous to humans. The main danger that crocodiles pose is not their ability to run after a person but their ability to strike before the person can react. The Saltwater and Nile Crocodiles are the most dangerous, killing hundreds of people each year in parts of south-east Asia and Africa. Mugger crocodiles and possibly the endangered Black Caiman, are also very dangerous to humans. American alligators are less aggressive and rarely assault humans without provocation. The most deaths in a single crocodile attack incident may have occurred during the Battle of Ramree Island, on February 19, 1945, in Burma.

Crocodile products
Crocodile leather can be made into goods such as wallets, briefcases, purses, belts and hats. Crocodile is consumed in some countries such as Australia, Ethiopia, Thailand, South Africa and also Cuba (in pickled form). It can also be found in specialty restaurants in some parts of the United States. The meat is white and its nutritional composition compares favourably with that of other meats. It does tend to have a slightly higher cholesterol level than other meats. Crocodile meat has a delicate flavour and its taste can be complemented by the use of marinades. Choice cuts of meat include backstrap and tail fillet.