A squad of RODENTS (Rodentia) dentition — the characteristic by which animals are combined in the rodent order and are different animals from any other groups. Show… the Incisors of rodents, located one on each side of the upper and lower jaw, very large, devoid of roots and grow continuously. Them the free end of the chisel is pointed. Grind off the uneven incisors in rodents and always stay sharp. In rodents, canines and no cheek teeth separated from incisors by a wide toothless gap — diastema. The total number of molars (with preparename) each side in upper jaw from 5 to 1, in the lower jaw 4 to 1. The decrease in the number of teeth in rodents is due to the front Predgorny corresponding small Predgorny the teeth of insectivores and bats, and then through the rear indigenous. Molars in rodents have broad chewing surface from rows of blunt tubercles (original structure), low transverse ridges, formed by compound tubercles, or their chewing surface becomes wrinkled. Some rodents formed a well-separated roots, but most roots are not formed, and in this case, teeth are constantly growing. The number of teeth and the structure of their occlusal surface is an important characteristics used to separate gryzunov different families, subfamilies and genera, and sometimes in the diagnosis of species.
The body size of rodents varied from small (less house mouse) to have a length of more than 1 m and weighing several tens of kilograms. The shape of the body and especially on the structure of the limbs of different rodents in connection with the adaptation to different conditions of existence.
Hair in rodents is usually well developed. Guard hairs of some rodents adapted to the needle. Collarbone usually available, but for many it is underdeveloped. Typical for rodents and a broad articular surface of the head lower jaw, allowing her to freely move not only sideways, but also forwards and backwards. Most rodents, except for dormice, has a long caecum. Cerebral hemispheres of rodents is small, not covering the cerebellum; its surface is smooth or shallow furrows. The uterus is two-horned rodents. Rodents inhabit all continents except Antarctica and most Islands of the World ocean, many of which they have been introduced by people. In the rodent joins more than one-third of present-day mammals that inhabit the globe (approximately 2500 species). They are grouped into more than 30 families. The exact amount a family of rodents have different taxonomists differ.