Ecureuil), properly the name of the wellknown red, bushy-tailed British arboreal mammal, Sciurus vulgaris, typifying the genus Sciurus and the family Sciuridae, but in a wider sense embracing all the rodents included in this and a few nearly allied genera.
For the characteristics of the family Sciuridae and the different squirrel-like genera by which it is represented, see Rodentia.
Beavers are nearly allied to the squirrels (Sciuridae), agreeing in certain structural peculiarities of the lower jaw and skull.
In the Sciuridae the two main bones (tibia and fibula) of the lower half of the leg are quite separate, the tail is round and hairy, and the habits are arboreal and terrestrial.
The uterus may be double, each division opening by a separate os uteri into a common vagina, as in Leporsdae, Sciuridae, and Hydrochoerus, or two-horned, as in most species.
Squirrel Group. - The Sciuroidea, which include the great group of squirrels, sousliks, marmots, &c., all comprised in the single family Sciuridae, differ from the sewellels in having large post-orbital processes to the skull (figs.
The Nannosciurinae, or second sub-family of Sciuridae, are represented only by the pigmy squirrels (Nannosciurus), characterized by their very short-crowned molars (which approximate to those of dormice in structure) and small premolars, of which the first upper pair is often deciduous, while the upper molars have only three oblique ridges.
Very noteworthy is the fact that, with the exception of Madagascar (and of course Australia) the squirrel family (Sciuridae) is also found in all parts of the world.
Forsyth-Major, "On some Miocene Squirrels, with Remarks on the Dentition and Classification of the Sciuridae," Proc. Zool.