Superregnum: Eukaryota
Cladus: Unikonta
Cladus: Opisthokonta
Cladus: Holozoa
Regnum: Animalia
Subregnum: Eumetazoa
Cladus: ParaHoxozoa
Cladus: Bilateria
Cladus: Nephrozoa
Superphylum: Deuterostomia
Phylum: Chordata
Cladus: Olfactores
Subphylum: Vertebrata
Infraphylum: Gnathostomata
Megaclassis: Osteichthyes
Cladus: Sarcopterygii
Cladus: Rhipidistia
Cladus: Tetrapodomorpha
Cladus: Eotetrapodiformes
Cladus: Elpistostegalia
Superclassis: Tetrapoda
Cladus: Reptiliomorpha
Cladus: Amniota
Cladus: Synapsida
Cladus: Eupelycosauria
Cladus: Metopophora
Cladus: Haptodontiformes
Cladus: Sphenacomorpha
Cladus: Sphenacodontia
Cladus: Pantherapsida
Cladus: Sphenacodontoidea
Cladus: Therapsida
Cladus: Theriodontia
Cladus: Eutheriodontia
Cladus: Cynodontia
Cladus: Epicynodontia
Cladus: Eucynodontia
Cladus: Probainognathia
Cladus: Prozostrodontia
Cladus: Mammaliamorpha
Cladus: Mammaliaformes
Classis: Mammalia
Cladus: Theriimorpha
Cladus: Theriiformes
Cladus: Trechnotheria
Cladus: Cladotheria
Cladus: Prototribosphenida
Cladus: Zatheria
Cladus: Tribosphenida
Subclassis: Theria
Cladus: Eutheria
Infraclassis: Placentalia
Magnordo: Boreoeutheria
Superordo: Euarchontoglires
Cladus: Gliriformes
Grandordo: Glires
Mirordo: Simplicidentata
Ordo: Rodentia
Subordo: Hystricomorpha
Infraordo: Hystricognathi
Classis: Mammalia
Ordo: Rodentia
Subordo: Hystricomorpha
Infraordo: Hystricognathi
Taxa: Caviomorpha – Hystricoidea – Phiomorpha
Name
Hystricognathi Tullberg, 1899
The Hystricognathi are an infraorder of rodents, distinguished from other rodents by the bone structure of their skulls. The masseter medialis (a jaw muscle) passes partially through a hole below each eye socket (called the infraorbital foramen) and connects to the bone on the opposite side. This, together with their lack of an infraorbital plate and the relative size of the infraorbital foramen, distinguishes hystricognaths from other rodent groups.
The 18 families within the Hystricognathi are divided into two parvorders, the Phiomorpha and the Caviomorpha. The Caviomorpha are mostly native to South America, with a few species in the Caribbean and North America, while the Phiomorpha occur in the Old World.
Skull of a nutria demonstrating the hystricognathous lower jaw and hystricomorphous zygomasseteric system
Behavior
Play behavior has been observed in seven hystricognath families. The caviomorphs chase each other, play-wrestle, and gallop. The longer-legged species chase more often than the shorter-legged species. They also rotate their heads and body muscles as a form of play.[1]
Phiomorphan hystricognath families
Bathyergidae (African mole rats)
Heterocephalidae (naked mole rats, monotypic taxon)
Hystricidae (Old World porcupines)
Petromuridae (dassie rat, monotypic taxon)
Thryonomyidae (cane rats)
Caviomorphan hystricognath families
Abrocomidae (chinchilla rats)
Capromyidae (hutias)
Caviidae (guinea pigs, wild cavies, and capybaras)
Chinchillidae (chinchillas and viscachas)
Ctenomyidae (tuco-tucos)
Cuniculidae (pacas)
Dasyproctidae (agoutis and acouchis)
Dinomyidae (pacaranas and their fossil relatives, including some of megafaunal size)
Echimyidae (spiny rats)
Erethizontidae (New World porcupines)
Myocastoridae (coypu)
Octodontidae (13 species including the degus)
See also
Sciurognathi
Hystricomorpha
References
Citations
Fagen, Robert. Animal Play Behavior. Oxford University Press, 1981.
Sources
Alfred L. Gardner Curator of North American mammals and Chief of Mammal Section, National Biological Service, Smithsonian Institution, National Museum of Natural History, Washington, DC, USA
Charles A. Woods Florida Museum of Natural History, University of Florida, Gainesville, FL 32611-2035
McKenna, Malcolm C. and Susan K. Bell 1997 Classification of mammals above the species level 631 Columbia University Press New York, New York, USA ISBN 0-231-11012-X
Wilson, Don E., and DeeAnn M. Reeder, eds. 1993 Mammal Species of the World: A Taxonomic and Geographic Reference, 2nd ed., 3rd printing xviii + 1207 Smithsonian Institution Press Washington, DC, USA ISBN 1-56098-217-9 Corrections were made to text at 3rd printing
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