It typifies not only the genus Chinchilla, but the family Chinchillidae, for the distinctive features of which see RODENTIA.
For the characteristics of the family Sciuridae and the different squirrel-like genera by which it is represented, see Rodentia.
The essential characteristic of the Cricetines is to be found in the upper cheek-teeth, which (as shown in the figure of those of Cricetus in the article RODENTIA) have their cusps arranged in two longitudinal rows separated by a groove.
Capybaras belong to the family Caviidae, the leading characteristics of which are given in Rodentia.
On these grounds, while admitting that they are allied to the rodents, it has been pointed out that they can scarcely be included in the Rodentia, and the order Proglires has in consequence been proposed for their reception.