Sciurognathi is a suborder of rodents that
includes squirrels, chipmunks, beavers, and many types of mice. The group is characterized by a specific shape to
the lower jaw. In sciurognaths, the angular process of the jaw
is in the same plane as the root of the incisors. This is in contrast to the suborder
Hystricognathi where the angular process is outside of the plane formed at the root of
the incisor due to the presence of a shelf for muscle attachment.
The sciurognathous condition is considered to be the primitive condition in rodents, and
is therefore not a good character according to cladistic philosophy. Although hystricognaths are almost universally accepted as representing a real evolutionary grouping, most researchers do not consider Sciurognathi as an equally valid group. In particular,
gundis are thought to be more closely related to the hystricognathous rodents than to other
sciurognaths. In spite of this, most texts continue to use these two suborders due primarily to a lack of a viable
alternative.
Alternatively, some texts group rodents into three suborders on the basis of the shape of the infraorbital canal. According to this taxonomy the rodents are divided into the suborders
Sciuromorpha, Hystricomorpha, and Myomorpha.
See also
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