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| Sciurognathi | |
|---|---|
 | |
| Mountain beaver (Aplodontia rufa) | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Rodentia |
| Suborder: | Sciurognathi |
| Infraorders | |
Sciurognathi is asuborder ofrodents that includessquirrels,chipmunks,beavers, and many types ofmice. The group is characterized by a specific shape to thelower jaw. In sciurognaths, theangular process of the jaw is in the same plane as the root of theincisors. This is in contrast to the suborderHystricognathi where the angular process is outside the plane formed at the root of the incisor due to the presence of a shelf for muscle attachment.[1]
The sciurognathous condition is considered to be theprimitive condition in rodents, and is therefore not a good character forcladistic analysis. Although hystricognaths are almost universally accepted as representing a realevolutionary 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 theinfraorbital canal. According to this taxonomy the rodents are divided into the subordersSciuromorpha,Hystricomorpha, andMyomorpha.