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.
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.