The Rodentia have a wider geographical range than any other order of terrestrial mammals, being, as already mentioned, represented by numerous members of the mouse-tribe (Muridae) even in Australasia.
Rodentia (Gnawing Mammals) :- a.
Whether the extinct Tillodontia are most nearly allied to the Rodentia, the Carnivora or the Ungulata, and whether they are really entitled to constitute an ordinal group by themselves, must remain for the present open questions.
(For the characteristics of the family and of its more important generic representatives, see RoDENTIA.) In the Egyptian jerboa the length of the body is 8 in., and that of the tail, which is long, cylindrical and covered with short hair terminated by a tuft, 10 in.
Although the British representatives of this group should undoubtedly retain their vernacular designations of water-rat and short-tailed field-mouse, the term "vole" is one of great convenience in zoology as a general one for all the members of the group. Systematically voles are classed in the mammalian order Rodentia, in which they constitute the typical section of the subfamily Microtinae in the Muridae, or mouse-group. As a group, voles are characterized by being more heavily built than rats and mice, and by their less brisk movements.