Lesson plan
Sciurognathi
Sciurognathi is a historical 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 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 for cladistic analysis. 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.
Article summary
Sciurognathi is a historical 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 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 for cladistic analysis. 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.
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Discussion questions
- Summarise the article in your own words. Which single claim would you verify first, and why?
- Which claim in this article is most likely to be revised as the sources update? How would you check its current status?
- If two sources disagreed about one of these facts, what would you need in order to trust one over the other?
Bibliography
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Key claims and bibliography are generated from the same tracked claims and sources as the article page.