The biggest difference - in their teeth. When closed, the jaws of a crocodile, you can see a big fourth tooth of the mandible , At the same alligator upper jaw closes these teeth , Also, they can be distinguished by the form of muzzle: that of a real crocodile snout sharp, V-shaped, an alligator - a dull, U-shaped.
The length of most crocodiles 2-5,5 m. Their appearance demonstrates the adaptation to life in the aquatic environment: the head is flat, with a long snout, the body flattened, powerful tail, compressed laterally, rather short legs. At the front legs - 5 fingers on the back - 4 (not the little finger), connected membrane. The eyes with vertically slit pupils are on top of the head, so that the animal can peek out of the water, exposing only the nose and out his eyes, nostrils and ear holes with water moving close valves.
Crocodile skin is covered with rectangular horny plates that are on the back and abdomen are arranged in regular rows. Under the dorsal and ventral plates under the less developed osteodermy (bony plates), forming a shell. Osteodermy accumulate in the daytime heat is supplied together with the sunlight. This crocodile's body temperature during the day varies from one degree , Crocodile should not be confused with the warm-blooded animals (birds and mammals), whose constant body temperature is maintained at the expense of its own metabolism.
Nasopharyngeal passage is separated from the oral cavity secondary bone-air, allowing the crocodile to keep the mouth open under water, while continuing to breathe through the nostrils exhibited over the water (hoany). And water in the windpipe does not miss a special valve at the bottom of the mouth (palatal zaveska), and air passes into the trachea to epipharungeal move behind the valve. Lightweight large, is more sophisticated, can accommodate a large supply of air through the lungs crocodile is able to regulate buoyancy , There is a diaphragm of the connective tissue, is activated by hepatic pump, in which the liver and freely connected to the pelvis pubic bone move in anteroposterior direction
Circulatory system crocodiles most advanced among the reptiles , Heart of a four-: has two atrial and two ventricular, completely separate partition. However, there is a mechanism for controlled mixing of arterial blood with venous blood due to conservation of both arches of the aorta, at the intersection where there is anastomosis (panitstsievo hole), and blood can flow from one arc to another.
The teeth of a crocodile of the same type, conical, hollow inside - in these cavities as wear and tear is developing new teeth , Teeth lifetime crocodile changed repeatedly. In this case the teeth of the upper and lower jaws are combined in such a way that is against one of the largest teeth jaw tries. odyatsya very small teeth the second , Teeth are sitting in the alveoli, as in mammals. The stomach has a thick muscular wall, it is usually tries odyat stones-gastrolity necessary crocodile for grinding food (according to another version, they move the center of gravity of a crocodile, adding that greater stability when sailing). Moving inside the abdominal cavity with a massive liver, the crocodile can change the center of gravity that allows him to take a more comfortable position during the movement of water and when he hunts by hiding under water.
Bodies selection and breeding
Bladder is not that seems to be associated with life in the water , Surplus intracavitary fluid output from the abdominal pores. Cloaca in the form of longitudinal cracks in the back of a male sexual organ is unpaired, on either side of him lay glands brown secret with a strong musky odor. Similar glands are on the lower side of the jaw , Secretion of musk glands is particularly intense during the breeding season, and probably the crocodiles of different sexes for tries ozhdeniya each other.
Nervous system and sense organs
On the development of the brain are higher than other crocodiles reptiles: the cerebral hemispheres have the bark. Of the senses crocodiles are the most developed sight and hearing. On the surface of crocodile jaws are numerous pressure receptors that allow him to feel the vibration coming from the animals tries odyaschihsya in water at a great distance.