(The Higher Reptiles)
The crocodiles belong to the family Crocodylidae, while alligators and caimans are placed in family Alligatoridae. The crocodile has a very long, narrow, V-shaped snout, while the alligator’s snout is wider and U-shaped. Because of the wide snout of the alligator it packs more crushing power to eat prey like turtles that constitute part of its diet. The narrow crocodile snout, although still very powerful, is not really suited for prey like turtles but is very versatile for fish and mammalian prey.
Another physical difference between the crocodile and the alligator is that the crocodile’s upper and lower jaws are nearly the same width, so the teeth are exposed all along the jaw line in an interlocking pattern, even when the mouth is closed. They also have a large 4th tooth on the lower jaw that fits in the depressions in the upper jaw just behind the nostrils. An alligator, on the other hand, has a wider upper jaw, so when its mouth is closed the teeth in the lower jaw fit into sockets of the upper jaw. Only the teeth of the upper jaw are exposed along the lower jaw line. Crocodiles have a lighter olive brown colour, while alligators appear blackish. Both crocodiles and alligators have dotted sensory pits along the upper and lower jaws that look almost like beard stubble. They detect slight changes in water pressure, which is believed to help the animals locate their prey. These sensory pits are called Dermal Pressure Receptors. In terms of nesting, crocodiles lay their eggs in mud or sand nests near brackish water, while alligators make their nests out of mounds of vegetation surrounding freshwater.
The crocodile’s biting force is more than 5,000 pounds per square inch compared to just 335 pounds per square inch for a rottweiler, 400 pounds for a large great white shark and 800-1000 pounds for a hyena. The jaws are opened by a very weak set of muscles.
The largest recorded crocodile was a giant saltwater crocodile that measured at 8.6 metres and weighed 1,352 kilograms was shot in Australia, Queensland in 1957. The largest living crocodile known is 7.1 metres long saltwater crocodile recorded in Orissa, India. It lives in Bhitarkanika Wildlife Sanctuary and in June 2006, was entered in the Guinness Book of World Records. Adult males can reach sizes of up to 6 or 7 metres but in general, males over 5 m in length are extremely rare. Females are smaller, and do not normally exceed 3 m, with 2.5 m being considered very large.
Crocodylus acutus, American Crocodile, in estuaries in Southern Florida, northwest South America and the Carrinbean. 6 m long.
Crocodylus cataphractus, Slender-snouted Crocodile (studies in DNA and morphology suggest that this species may be more basal than Crocodylus, and therefore belongs in its own genus, Mecistops)
Crocodylus intermedius, Orinoco Crocodile, in Amazon River of South America.
Crocodylus johnsoni, Freshwater Crocodile of Northern Australia.
Crocodylus mindorensis, Philippines Crocodile.
Crocodylus moreletii, Morelet’s Crocodile or Mexican Crocodile.
Crocodylus niloticus, Nile Crocodile or African Crocodile, 7 m long.
Crocodylus novaeguineae, New Guinea Crocodile, also occurs in parts of Philippines.
Crocodylus palustris, Mugger or Indian Crocodile of India, Bangladesh and Sri Lanka.
Crocodylus porosus, Saltwater Crocodile or Estuarine Crocodile, Southern Asia to Australia. 7 m long.
Crocodylus rhombifer, Cuban Crocodile.
Crocodylus siamensis, Siamese Crocodile.
Osteolaemus means “bony throat”, derived from osteon=bone + laimos=throat, referring to the extensive bony plates found in the neck and belly.
Osteolaemus tetraspis, The Dwarf Crocodile. The species name tetraspis=four shields, refers to the cluster of four bony plates (nuchal scales) on the back of the neck.
It has the following 2 subspecies:
O. tetraspis tetraspis, found in western Africa.
O. tetraspis osborni, found in Congo (formerly Zaire). This species was formerly known as Osteoblepharon osborni.
Alligators differ from crocodiles principally in having wider and shorter heads, with more obtuse snouts; in having the fourth, enlarged tooth of the under jaw received, not into an external notch, but into a pit formed for it within the upper one; in lacking a jagged fringe which appears on the hind legs and feet of the crocodile; in having the toes of the hind feet webbed not more than half way to the tips; and an intolerance to salinity, alligators strongly preferring fresh water, while crocodiles can tolerate salt water due to specialized glands for filtering out salt. In general, crocodiles tend to be more dangerous to humans than alligators.
Chinese Alligator(Alligator sinensis)
It is smaller, about 5 ft long. Found along the lower Yangtze River in the provinces of Jiangsu, Zhejiang, and Anhui. Unlike the American Alligator, the Chinese Alligator is fully armored; even the belly is armored, which is a feature of only a few crocodilians.
American Alligator(Alligator mississippiensis)
The American alligator is a large, semi-aquatic, armoured reptile that is related to crocodiles. Their body alone ranges from 6 – 14 feet long. Almost black in colour, the it has prominent eyes and nostrils with coarse scales over the entire body. It has a large, long head with visible upper teeth along the edge of the jaws. Its front feet have 5 toes, while rear feet have 4 toes that are webbed. American alligators are found from the southern Virginia-North Carolina border, along the Atlantic coast to Florida and along the Gulf of Mexico as far west as the Rio Grande in Texas.