Sciuromorpha ("squirrel-like") is a rodent

clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...

that includes several different rodent families. It includes all members of the Sciuridae (the squirrel family) as well as the mountain beaver species. Traditionally, the term has been defined on the basis of the shape of the infraorbital canal. A sciuromorphous

zygomasseteric system The zygomasseteric system (or zygomasseteric structure) in rodents is the anatomical arrangement of the masseter muscle of the jaw and the zygomatic arch of the skull. The anteroposterior or propalinal (front-to-back) motion of the rodent jaw ...

is characterized by attachment of the lateral masseter muscle along the side of the rostrum. Unlike

hystricomorphous The zygomasseteric system (or zygomasseteric structure) in rodents is the anatomical arrangement of the masseter muscle of the jaw and the zygomatic arch of the skull. The anteroposterior or propalinal (front-to-back) motion of the rodent jaw ...

and myomorphous rodents, the medial masseter muscle does not pass through the infraorbital canal. Among extant rodents, only the families Sciuridae, Castoridae, Heteromyidae, and Geomyidae are truly sciuromorphous. Some authorities would exclude the Geomyidae and Heteromyidae from that list due to the attachment of the medial masseter directly behind the zygomatic arch. Carleton and Musser (2005) redefined the rodent suborders on morphological and

molecular A molecule is a group of two or more atoms held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions which satisfy this criterion. In quantum physics, organic chemistry, and bioche ...

grounds. They defined the Sciuromorpha as including three families, Sciuridae, Aplodontiidae, and Gliridae. Of these, only the Sciuridae are truly sciuromorphous. The Aplodontiidae are protrogomorphous and the Gliridae are myomorphous. The connection between Aplodontiidae and Sciuridae has been proposed numerous times in the past. The two families have been united into a common infraorder (Sciurida) or

superfamily SUPERFAMILY is a database and search platform of structural and functional annotation for all proteins and genomes. It classifies amino acid sequences into known structural domains, especially into SCOP superfamilies. Domains are functional, str ...

(Sciuroidea). It has long been suggested that dormice (Gliridae) are not particularly related to the Myomorpha, and their zygomasseteric structure has been termed "pseudomyomorphy". The connection between squirrels and dormice has been almost exclusively suggested through genetic studies, and to a lesser degree via the fossil rodent '' Reithroparamys''.

Current families

The suborder Sciuromorpha contains 307 living species in 61 genera and three families. At least three extinct families are also recognised. * † Allomyidae * Aplodontiidae – mountain beaver * † Mylagaulidae * Sciuridae – squirrels, chipmunks, marmots, flying squirrels, etc. * † Reithroparamyidae * Gliridae – dormice

Historical families

* Castoridae – beavers * Geomyidae – pocket gophers * Heteromyidae – pocket mice, kangaroo rats, and kangaroo mice * Pedetidae – springhares * Anomaluridae - anomalures

References

* Carleton, M. D. and G. G. Musser (2005). "Order Rodentia". pp. 745–752 in ''Mammal Species of the World A Taxonomic and Geographic Reference'' (D. E. Wilson and D. M. Reeder eds.). Baltimore: Johns Hopkins University Press.

External links

* {{Taxonbar, from=Q724477 Rodent taxonomy Mammal suborders Extant Eocene first appearances Taxa named by Johann Friedrich von Brandt