Zygomatic plate
Encyclopedia
In rodent
anatomy, the zygomatic plate is a bony plate derived from the flattened front part of the zygomatic arch
(cheekbone). At the back, it connects to the front (maxillary) root of the zygomatic arch, and at the top it is connected to the rest of the skull via the antorbital bridge. It is part of the maxilla
ry bone, or upper jaw, which also contains the upper cheekteeth. Primitively, rodents have a nearly horizontal zygomatic plate. In association with specializations in zygomasseteric system
, several distinct morphologies have developed across the order.
The term is also used for an analogous structure in some South American typotheres, including Pseudotypotherium and Medistylus.
includes three families. Squirrel
s (family Sciuridae) tend to have broad zygomatic plate that extend above the infraorbital foramen
. The mountain beaver
(Aplodontia rufa), the only surviving member of its family, retains the primitive narrow and low plate. The dormice (Gliridae) have broad, high zygomatic plates, except for Graphiurus
, which has a lower plate.
, which includes the beaver
s, pocket gopher
s, and pocket mice
, tend to have broad zygomatic plate that extend above the infraorbital foramen
.
is a small suborder, containing only two families. Anomaluridae have a low and narrow zygomatic plate. Members of the subfamily Idiurinae are atypical in having the zygomatic plate extended forward nearly to the incisors. The condition in the springhaas (Pedetes) is similar.
is the largest suborder of rodents. In the most numerous subgroup, the Muroidea
(including all living families except Dipodidae), the zygomatic plate is generally broad and tilted upwards. Muroids may have the plate extending in front of the front (maxillary) root of the actual zygomatic arch, creating a zygomatic notch. In some, the plate extends at the front into a spinous process
, the zygomatic spine.
, which have hystricomorphous zygomasseteric morphology, have nearly horizontal, narrow zygomatic plates.
ly specialized family Spalacidae
shows peculiarities in the condition of the zygomatic plate. In Tachyoryctes
and the Rhizomyinae
, it is tilted upward and fused to the sides of the snout (rostrum). In the Spalacinae and Myospalacinae, on the other hand, the plate is tilted downward into an almost horizontal position.
(Calomyscus), the only member of its family, has a straight front margin on the zygomatic plate.
is restricted to Africa.
Dendromus
has a narrow zygomatic plate, as do Steatomys
and Prionomys.
Brachyuromys
has an arvicoline-like high zygomatic plate. In Eliurus
, the front border of the plate is straight. Nesomys
has a low zygomatic plate. In Hypogeomys, it is broad, but rather low.
is the order's largest family, and contains several subfamilies.
Deomys, a member of the Deomyinae
, has an unusually low zygomatic plate, as does Lophuromys, a member of the same subfamily.
Most members of the subfamily Murinae
, the Old World rats and mice, have a fairly broad zygomatic plate with a well-developed zygomatic notch. A zygomatic spine is developed in some Australian genera, including Notomys and some Pseudomys
. Except for Xeromys, Hydromys
and related genera ("hydromyines") have a narrow plate, lacking the notch, as does Hyomys
, Macruromys
, Crunomys
, and Rhynchomys. The Philippine Batomys
, Carpomys
, and Crateromys
have well-developed zygomatic plates, reminiscent of those in Arvicolinae. Phloeomys
has a broad zygomatic plate.
is the order's second largest, containing several subfamilies and hundreds of species.
The subfamily Arvicolinae
, the voles and lemmings, has the zygomatic plate tilted upwards very strongly.
In the subfamily Tylomyinae
, Nyctomys has a narrow zygomatic plate.
Among members of the Neotominae
, Baiomys
, Reithrodontomys
, Onychomys, and Peromyscus
has a narrow zygomatic plate.
Members of the subfamily Sigmodontinae
, which includes a number of tribes, usually have the antorbital bridge below the upper surface of the skull. Most have a zygomatic notch. The extent of the zygomatic plate at the back is also variable within Sigmodontinae, with some having the plate extending back to the level of the first upper molar and others having shorter plates.
Members of the semiaquatic tribe Ichthyomyini are unique among the Sigmodontinae in lacking the zygomatic notch. In ichthyomyines, the development of the zygomatic plate is correlated with the development of the teeth: those species with large molars and small incisors, including species of Anotomys and Rheomys
, have slender plates that do not extend back to the first molars, whereas those with larger incisors and smaller molars, including some Ichthyomys
and Neusticomys
, have broader zygomatic plates that do reach the level of the first molars.
The genus Sigmodon, which is classified in its own tribe, has a broad zygomatic plate and a zygomatic spine. Relative width of the zygomatic plate can distinguish some species of Sigmodon.
Most members of the tribe Phyllotini have the antorbital bridge located higher than is usual in Sigmodontinae (Calomys and Andalgalomys
show the normal sigmodontine condition). A similar condition characterizes Euneomys
, Neotomys, Reithrodon
, which are no longer considered phyllotines, but to an even larger extent than in most actual phyllotines; in Euneomys, the antorbital bridge is inserted on the upper surface of the skull. Most phyllotines have zygomatic spines, but the structure is more well-developed in Reithrodon. The zygomatic plate not extending backwards to the first molars is a diagnostic character of phyllotines.
Most thomasomyines lack a well-developed zygomatic notch. The genus Rhipidomys
has a narrow zygomatic plate, no zygomatic spine and only a narrow notch. Thomasomys
shares a narrow zygomatic plate.
In the Akodontini
, Oxymycterus
and Lenoxus have a low zygomatic plate, similar to that of Lophuromys. Scapteromys
shares a low plate. In Akodon
, the plate is narrow, as in many others akodontine; this is extremely so in Blarinomys.
The tribe Abrotrichini
is characterized by a narrow zygomatic plate, without an extension at the upper border.
In the tribe Oryzomyini
, the configuration of the zygomatic plate is variable. Most have a well-developed zygomatic notch. In the three related genera Holochilus
, Pseudoryzomys, and Lundomys, this extension has further developed into a zygomatic spine. In contrast, Microryzomys
, Oreoryzomys, Oecomys
, Scolomys
, and Sigmodontomys aphrastus lack a well-defined notch and do not have the plate extending appreciably in front of the root of the zygomatic arch. The zygomatic plate extending back to the level of the upper first molar is a putative synapomorphy
of Clade C within Oryzomyini.
The sigmodontine Juliomys pictipes has an almost vertical zygomatic plate.
Rodent
Rodentia is an order of mammals also known as rodents, characterised by two continuously growing incisors in the upper and lower jaws which must be kept short by gnawing....
anatomy, the zygomatic plate is a bony plate derived from the flattened front part of the zygomatic arch
Zygomatic arch
The zygomatic arch or cheek bone is formed by the zygomatic process of temporal bone and the temporal process of the zygomatic bone , the two being united by an oblique suture; the tendon of the Temporalis passes medial to the arch to gain insertion into the coronoid process...
(cheekbone). At the back, it connects to the front (maxillary) root of the zygomatic arch, and at the top it is connected to the rest of the skull via the antorbital bridge. It is part of the maxilla
Maxilla
The maxilla is a fusion of two bones along the palatal fissure that form the upper jaw. This is similar to the mandible , which is also a fusion of two halves at the mental symphysis. Sometimes The maxilla (plural: maxillae) is a fusion of two bones along the palatal fissure that form the upper...
ry bone, or upper jaw, which also contains the upper cheekteeth. Primitively, rodents have a nearly horizontal zygomatic plate. In association with specializations in zygomasseteric system
Zygomasseteric system
The zygomasseteric system in rodents is the anatomical arrangement of the masseter muscle of the jaw and the zygomatic arch of the skull...
, several distinct morphologies have developed across the order.
The term is also used for an analogous structure in some South American typotheres, including Pseudotypotherium and Medistylus.
Function
The zygomatic plate serves to resist muscular tension resulting from the contraction of the incisors by the anterior deep masseter muscle; thus, rodents which pulverize hard food with the incisors tend to have broader zygomatic plates than those that rather use their molars for this purpose.Hystricomorpha
The members of this large and diverse suborder have a narrow, low zygomatic plate.Sciuromorpha
The suborder SciuromorphaSciuromorpha
The term Sciuromorpha has referred to numerous groups of rodents, but the only family common to all variations is the Sciuridae, the squirrels. Most definitions also include the Mountain Beaver....
includes three families. Squirrel
Squirrel
Squirrels belong to a large family of small or medium-sized rodents called the Sciuridae. The family includes tree squirrels, ground squirrels, chipmunks, marmots , flying squirrels, and prairie dogs. Squirrels are indigenous to the Americas, Eurasia, and Africa and have been introduced to Australia...
s (family Sciuridae) tend to have broad zygomatic plate that extend above the infraorbital foramen
Infraorbital foramen
Above the canine fossa is the infraorbital foramen, the end of the infraorbital canal; it transmits the infraorbital artery, vein, and infraorbital nerve.-External links: *...
. The mountain beaver
Mountain Beaver
The Mountain Beaver is the most primitive extant rodent. Not to be confused with the North American beaver Castor canadensis, or its relative the Eurasian beaver, Castor fiber, it has several common names including Aplodontia, Boomer, Ground Bear, and Giant Mole...
(Aplodontia rufa), the only surviving member of its family, retains the primitive narrow and low plate. The dormice (Gliridae) have broad, high zygomatic plates, except for Graphiurus
Graphiurus
The African dormice, Graphiurus, are a genus of dormouse that live throughout sub-Saharan Africa in a variety of habitats. They are very agile climbers and have bushy tails...
, which has a lower plate.
Castorimorpha
Members of the suborder CastorimorphaCastorimorpha
Castorimorpha is the suborder of rodents containing the beavers, the pocket gophers, and the kangaroo rats and mice.-Taxonomy:*Suborder Castorimorpha**Superfamily Castoroidea***Family †Eutypomyidae***Family Castoridae - beavers...
, which includes the beaver
Beaver
The beaver is a primarily nocturnal, large, semi-aquatic rodent. Castor includes two extant species, North American Beaver and Eurasian Beaver . Beavers are known for building dams, canals, and lodges . They are the second-largest rodent in the world...
s, pocket gopher
Pocket gopher
The pocket gophers are burrowing rodents of the family Geomyidae. These are the "true" gophers, though several ground squirrels of the family Sciuridae are often called gophers as well...
s, and pocket mice
Heteromyidae
The family of rodents that include kangaroo rats, kangaroo mice and rock pocket mice is the Heteromyidae family. Most heteromyids live in complex burrows within the deserts and grasslands of western North America, though species within the Heteromys and Liomys genera are also found in forests and...
, tend to have broad zygomatic plate that extend above the infraorbital foramen
Infraorbital foramen
Above the canine fossa is the infraorbital foramen, the end of the infraorbital canal; it transmits the infraorbital artery, vein, and infraorbital nerve.-External links: *...
.
Anomaluromorpha
AnomaluromorphaAnomaluromorpha
Anomaluromorpha is the name given to a clade that unites the anomalures with the springhare. It has alternately been designated as either a suborder or infraorder...
is a small suborder, containing only two families. Anomaluridae have a low and narrow zygomatic plate. Members of the subfamily Idiurinae are atypical in having the zygomatic plate extended forward nearly to the incisors. The condition in the springhaas (Pedetes) is similar.
Myomorpha
MyomorphaMyomorpha
Suborder Myomorpha contains 1,137 species of mouse-like rodents, nearly a quarter of all mammal species. Included are mice, rats, gerbils, hamsters, lemmings and voles. They are grouped according to the structure of the jaw and the structure of the molar teeth. Both their medial and lateral...
is the largest suborder of rodents. In the most numerous subgroup, the Muroidea
Muroidea
Muroidea is a large superfamily of rodents. It includes hamsters, gerbils, true mice and rats, and many other relatives. They occupy a vast variety of habitats on every continent except Antarctica. Some authorities have placed all members of this group into a single family, Muridae, due to...
(including all living families except Dipodidae), the zygomatic plate is generally broad and tilted upwards. Muroids may have the plate extending in front of the front (maxillary) root of the actual zygomatic arch, creating a zygomatic notch. In some, the plate extends at the front into a spinous process
Process (anatomy)
In anatomy, a process is a projection or outgrowth of tissue from a larger body. The vertebra has several kinds of processes,such as: transverse process, prezygapophysis, postzygapophysis.-Examples:Examples of processes include:...
, the zygomatic spine.
Dipodidae
Members of the family DipodidaeDipodidae
The Dipodidae, or dipodids, are a family of rodents found across the northern hemisphere. This family includes over 50 species among the 16 genera....
, which have hystricomorphous zygomasseteric morphology, have nearly horizontal, narrow zygomatic plates.
Platacanthomyidae
Members of the small family Platacanthomyidae have a relatively narrow zygomatic plate.Spalacidae
The fossorialFossorial
A fossorial organism is one that is adapted to digging and life underground such as the badger, the naked mole rat, and the mole salamanders Ambystomatidae...
ly specialized family Spalacidae
Spalacidae
The Spalacidae, or spalacids are a family of rodents in the large and complex superfamily Muroidea. They are native to eastern Asia, the Horn of Africa, the Middle East, and south-eastern Europe. It includes the blind mole rats, bamboo rats, root rats, and zokors...
shows peculiarities in the condition of the zygomatic plate. In Tachyoryctes
Tachyoryctes
Tachyoryctes is a genus of rodent in the Spalacidae family.It contains the following species:* Ankole Mole Rat * Mianzini Mole Rat * Audacious Mole Rat...
and the Rhizomyinae
Rhizomyinae
The subfamily Rhizomyinae of rodents includes the Asian bamboo rats and certain of the African mole rats. The subfamily is grouped with the Spalacinae and the Myospalacinae into a family of fossorial muroid rodents basal to the other Muroidea....
, it is tilted upward and fused to the sides of the snout (rostrum). In the Spalacinae and Myospalacinae, on the other hand, the plate is tilted downward into an almost horizontal position.
Calomyscidae
The mouse-like hamsterMouse-like hamster
thumb|200px|rightthumb|200px|right|Mouse-like hamster using its tail for balance while standing on a branch .Mouse-like hamsters are a group of small rodents found in Syria, Azerbaijan, Iran, Turkmenistan, Afghanistan, and Pakistan...
(Calomyscus), the only member of its family, has a straight front margin on the zygomatic plate.
Nesomyidae
The family NesomyidaeNesomyidae
Nesomyidae is a family of African rodents in the large and complex superfamily Muroidea. It includes several subfamilies, all of which are native to either continental Africa or to Madagascar...
is restricted to Africa.
Dendromus
Dendromus
Mice in the genus Dendromus are commonly referred to as African climbing mice or tree mice, although these terms are often used to describe all members of the subfamily Dendromurinae...
has a narrow zygomatic plate, as do Steatomys
Steatomys
Steatomys is a genus of rodent in the Nesomyidae family.It contains the following species:* Bocage's African Fat Mouse * Northwestern Fat Mouse * Dainty Fat Mouse...
and Prionomys.
Brachyuromys
Brachyuromys
Brachyuromys is a genus of rodent in the family Nesomyidae.It contains the following species:* Betsileo Short-tailed Rat * Gregarious Short-tailed Rat...
has an arvicoline-like high zygomatic plate. In Eliurus
Eliurus
Eliurus is a genus of rodent in the family Nesomyidae.It contains the following species:* Tsingy Tufted-tailed Rat * Ankarana Special Reserve Tufted-tailed Rat...
, the front border of the plate is straight. Nesomys
Nesomys
Nesomys is a genus of rodent in the family Nesomyidae. It is found only on Madagascar, and contains the following species:* White-bellied Nesomys * Western Nesomys * Nesomys narindaensis †...
has a low zygomatic plate. In Hypogeomys, it is broad, but rather low.
Muridae
MuridaeMuridae
Muridae is the largest family of mammals. It contains over 600 species found naturally throughout Eurasia, Africa, and Australia. They have been introduced worldwide. The group includes true mice and rats, gerbils, and relatives....
is the order's largest family, and contains several subfamilies.
Deomys, a member of the Deomyinae
Deomyinae
The subfamily Deomyinae consists of four genera of mouse-like rodents that were placed in the subfamilies Murinae and Dendromurinae until very recently. They are sometimes called Acomyinae, particularly in references that predate the discovery that the link rat, Deomys ferugineus, is part of the...
, has an unusually low zygomatic plate, as does Lophuromys, a member of the same subfamily.
Most members of the subfamily Murinae
Murinae
The Old World rats and mice, part of the subfamily Murinae in the family Muridae, comprise at least 519 species. This subfamily is larger than all mammal families except the Cricetidae and Muridae, and is larger than all mammal orders except the bats and the remainder of the...
, the Old World rats and mice, have a fairly broad zygomatic plate with a well-developed zygomatic notch. A zygomatic spine is developed in some Australian genera, including Notomys and some Pseudomys
Pseudomys
Pseudomys is a genus of rodent that contains a wide variety of mice native to Australia and New Guinea. They are among the few terrestrial placental mammals that colonised Australia without human intervention.-Natural history:...
. Except for Xeromys, Hydromys
Hydromys
Hydromys is a genus of rodents in the subfamily Murinae.- List of species :Genus Hydromys - water rats*Rakali, Hydromys chrysogaster E...
and related genera ("hydromyines") have a narrow plate, lacking the notch, as does Hyomys
Hyomys
The White-eared giant rats, genus Hyomys, are a group of Old World rats from New Guinea.-Species:Genus Hyomys - white-eared rats*Western White-eared Giant Rat, Hyomys dammermani Stein, 1933...
, Macruromys
Macruromys
Macruromys is a genus of rodent in the family Muridae.It contains the following species:* Lesser Small-toothed Rat * Eastern Small-toothed Rat...
, Crunomys
Crunomys
Crunomys is a genus of rodent in the family Muridae.It contains the following species:* Celebes Shrew Rat * Northern Luzon Shrew Rat * Mindanao Shrew Rat...
, and Rhynchomys. The Philippine Batomys
Batomys
Batomys is a genus of rodent from the Philippines.-Species:Genus Batomys - Luzon and Mindanao forest rats*Large-toothed Hairy-tailed Rat, Batomys dentatus*Luzon Hairy-tailed Rat, Batomys granti...
, Carpomys
Carpomys
Carpomys is a genus of rodent in the family Muridae.It contains the following species:* Short-footed Luzon Tree Rat * White-bellied Luzon Tree Rat...
, and Crateromys
Crateromys
Crateromys is a genus of rodent, native to the Philippines, in the family Muridae.It contains four species:* Dinagat Bushy-Tailed Cloud Rat * Giant Bushy-Tailed Cloud Rat...
have well-developed zygomatic plates, reminiscent of those in Arvicolinae. Phloeomys
Phloeomys
Phloeomys is a genus of rodent in the family Muridae.It contains the following species:* Southern Giant Slender-Tailed Cloud Rat * Northern Luzon Giant Cloud Rat...
has a broad zygomatic plate.
Cricetidae
The family CricetidaeCricetidae
The Cricetidae are a family of rodents in the large and complex superfamily Muroidea. It includes true hamsters, voles, lemmings, and New World rats and mice...
is the order's second largest, containing several subfamilies and hundreds of species.
The subfamily Arvicolinae
Arvicolinae
The Arvicolinae are a subfamily of rodents that includes the voles, lemmings, and muskrats. They are most closely related to the other subfamilies in the Cricetidae . Some authorities place the subfamily Arvicolinae in the family Muridae along with all other members of the superfamily Muroidea...
, the voles and lemmings, has the zygomatic plate tilted upwards very strongly.
In the subfamily Tylomyinae
Tylomyinae
The subfamily Tylomyinae consists of several species of New World rats and mice including the vesper and climbing rats. They are not as well known as their relatives in the subfamilies Sigmodontinae and Neotominae...
, Nyctomys has a narrow zygomatic plate.
Among members of the Neotominae
Neotominae
Neotominae is a subfamily of the family Cricetidae. It consists of four tribes, 16 genera, and many species of New World rats and mice, predominantly found in North America. Among them are the well-known deer mice, white-footed mice, packrats, and grasshopper mice.Neotomines are related to the...
, Baiomys
Baiomys
Baiomys is the genus of New World pygmy mice. Together with Scotinomys, it forms the tribe Baiomyini. It currently contains two extant species:*Southern Pygmy Mouse, Baiomys musculus*Northern Pygmy Mouse, Baiomys taylori-References:...
, Reithrodontomys
Reithrodontomys
Reithrodontomys is the genus of groove-toothed New World harvest mice.-Species:This genus contains twenty species:*Guerrero Harvest Mouse *Short-Nosed Harvest Mouse...
, Onychomys, and Peromyscus
Peromyscus
The genus Peromyscus contains the animal species commonly referred to as deer mice. This is a genus of New World mouse only distantly related to the common house mouse and laboratory mouse, Mus musculus...
has a narrow zygomatic plate.
Members of the subfamily Sigmodontinae
Sigmodontinae
The subfamily Sigmodontinae is one of the most diverse groups of mammals. It includes New World rats and mice, with at least 376 species. Many authorities include the Neotominae and Tylomyinae as part of a larger definition of Sigmodontinae. When those genera are included, the species count...
, which includes a number of tribes, usually have the antorbital bridge below the upper surface of the skull. Most have a zygomatic notch. The extent of the zygomatic plate at the back is also variable within Sigmodontinae, with some having the plate extending back to the level of the first upper molar and others having shorter plates.
Members of the semiaquatic tribe Ichthyomyini are unique among the Sigmodontinae in lacking the zygomatic notch. In ichthyomyines, the development of the zygomatic plate is correlated with the development of the teeth: those species with large molars and small incisors, including species of Anotomys and Rheomys
Rheomys
Rheomys is a genus of semiaquatic rodents in the family Cricetidae.It contains the following species:* Mexican Water Mouse * Goldman's Water Mouse * Thomas's Water Mouse...
, have slender plates that do not extend back to the first molars, whereas those with larger incisors and smaller molars, including some Ichthyomys
Ichthyomys
Ichthyomys is a genus of semiaquatic rodents in the family Cricetidae.It contains the following species:* Crab-eating Rat * Pittier's Crab-eating Rat...
and Neusticomys
Neusticomys
Neusticomys is a genus of semiaquatic South American rodents in the family Cricetidae.It contains the following species:* Ferreira's Fish-eating Rat * Montane Fish-eating Rat...
, have broader zygomatic plates that do reach the level of the first molars.
The genus Sigmodon, which is classified in its own tribe, has a broad zygomatic plate and a zygomatic spine. Relative width of the zygomatic plate can distinguish some species of Sigmodon.
Most members of the tribe Phyllotini have the antorbital bridge located higher than is usual in Sigmodontinae (Calomys and Andalgalomys
Andalgalomys
Andalgalomys is a genus of rodent in the family Cricetidae.It contains the following species:* Olrog's Chaco Mouse * Pearson's Chaco Mouse * Roig's Chaco Mouse...
show the normal sigmodontine condition). A similar condition characterizes Euneomys
Euneomys
Euneomys is a genus of rodent in the family Cricetidae.It contains the following species:* Patagonian Chincilla Mouse * Burrowing Chincilla Mouse * Biting Chincilla Mouse...
, Neotomys, Reithrodon
Reithrodon
Reithrodon is a genus of rodent in the family Cricetidae.It contains the following species:* Bunny Rat * Naked-soled Conyrat...
, which are no longer considered phyllotines, but to an even larger extent than in most actual phyllotines; in Euneomys, the antorbital bridge is inserted on the upper surface of the skull. Most phyllotines have zygomatic spines, but the structure is more well-developed in Reithrodon. The zygomatic plate not extending backwards to the first molars is a diagnostic character of phyllotines.
Most thomasomyines lack a well-developed zygomatic notch. The genus Rhipidomys
Rhipidomys
Rhipidomys is a genus of rodents in the family Cricetidae, comprising at least 18 species of climbing mouse:* Southern Climbing Mouse * Cariri Climbing Mouse...
has a narrow zygomatic plate, no zygomatic spine and only a narrow notch. Thomasomys
Thomasomys
Thomasomys is a genus of rodent in the family Cricetidae, named after British zoologist Oldfield Thomas. It contains the following species:* Anderson's Oldfield Mouse * Apeco Oldfield Mouse...
shares a narrow zygomatic plate.
In the Akodontini
Akodontini
Akodontini is the second most speciose tribe of the subfamily Sigmodontinae. It includes at least 106 living species in 19 genera and is distributed mainly in the southern half of South America, with only two genera extending into Guyana and Venezuela . It also includes genera previously placed in...
, Oxymycterus
Oxymycterus
Oxymycterus is the genus of hocicudos. They are rat-like animals endemic to South America.Species listing:Oxymycterus is the genus of hocicudos. They are rat-like animals endemic to South America.Species listing:...
and Lenoxus have a low zygomatic plate, similar to that of Lophuromys. Scapteromys
Scapteromys
Scapteromys is a genus of South American rodents in the tribe Akodontini of family Cricetidae. Two species are known, found in northern Argentina, southern Brazil, Paraguay and Uruguay...
shares a low plate. In Akodon
Akodon
Akodon is a genus consisting of South American grass mice. They mostly occur south of the Amazon Basin and along the Andes north to Venezuela, but are absent from much of the basin itself, the far south of the continent, and the lowlands west of the Andes. Akodon is one of the most species-rich...
, the plate is narrow, as in many others akodontine; this is extremely so in Blarinomys.
The tribe Abrotrichini
Abrotrichini
Abrotrichini, also known as the Andean clade or southern Andean clade, is a tribe of rodents in the subfamily Sigmodontinae. It includes about fifteen species in five genera, distributed in South America from southern Peru to southernmost South America, including the Patagonian steppes...
is characterized by a narrow zygomatic plate, without an extension at the upper border.
In the tribe Oryzomyini
Oryzomyini
Oryzomyini is a tribe of rodents in the subfamily Sigmodontinae of family Cricetidae. It includes about 120 species in about thirty genera, distributed from the eastern United States to the southernmost parts of South America, including many offshore islands...
, the configuration of the zygomatic plate is variable. Most have a well-developed zygomatic notch. In the three related genera Holochilus
Holochilus
Holochilus is a genus of semiaquatic rodents in the tribe Oryzomyini of family Cricetidae, sometimes called marsh rats. It contains three living species, Holochilus brasiliensis, Holochilus chacarius, and Holochilus sciureus, which are widely distributed in South America east of the Andes, and a...
, Pseudoryzomys, and Lundomys, this extension has further developed into a zygomatic spine. In contrast, Microryzomys
Microryzomys
Microryzomys is a genus of rodent in the tribe Oryzomyini of family Cricetidae. It is closely related to Oreoryzomys, Oligoryzomys, and Neacomys. It contains two species, both restricted to the Andes: Microryzomys altissimus and Microryzomys minutus.-Literature cited:*Musser, G.G. and Carleton,...
, Oreoryzomys, Oecomys
Oecomys
Oecomys is a genus of rodent within the tribe Oryzomyini of family Cricetidae. It contains about 17 species, which live in trees and are distributed across forested parts of South America, extending into Panama and Trinidad.-Literature cited:...
, Scolomys
Scolomys
Scolomys is a genus of rodent in the tribe Oryzomyini of family Cricetidae. Some evidence suggests that it is related to Zygodontomys. It is characterized, among other traits, by spiny fur. It contains two species, Scolomys melanops and Scolomys ucayalensis.-Literature cited:*Musser, G.G. and...
, and Sigmodontomys aphrastus lack a well-defined notch and do not have the plate extending appreciably in front of the root of the zygomatic arch. The zygomatic plate extending back to the level of the upper first molar is a putative synapomorphy
Synapomorphy
In cladistics, a synapomorphy or synapomorphic character is a trait that is shared by two or more taxa and their most recent common ancestor, whose ancestor in turn does not possess the trait. A synapomorphy is thus an apomorphy visible in multiple taxa, where the trait in question originates in...
of Clade C within Oryzomyini.
The sigmodontine Juliomys pictipes has an almost vertical zygomatic plate.
Literature cited
- Carleton, M.D. and Musser, G.G. 2005. Order Rodentia. Pp. 745–752 in Wilson, D.E. and Reeder, D.M. (eds.). Mammal Species of the World: a taxonomic and geographic reference. 3rd ed. Baltimore: The Johns Hopkins University Press, 2 vols., 2142 pp. ISBN 978-0-8018-8221-0
- D'Elía, G., Pardiñas, U.F.J., Teta, P. and Patton, J.L. 2007. Definition and diagnosis of a new tribe of sigmodontine rodents (Cricetidae: Sigmodontinae), and a revised classification of the subfamily. Gayana 71(2):187–194.
- Ellerman, J.R. 1940. The families and genera of living rodents. Volume I. Rodents other than Muridae. London: Printed by order of the Trustees of the British Museum, 689 pp.
- Ellerman, J.R. 1941. The families and genera of living rodents. Volume II. Family Muridae. London: Printed by order of the Trustees of the British Museum, 690 pp.
- Jenkins, P.D., Kilpatrick, C.W., Robinson, M.F. & Timmins, R.J. 2005. Morphological and molecular investigations of a new family, genus and species of rodent (Mammalia: Rodentia: Hystricognatha) from Lao PDR. Systematics and Biodiversity 2(4):419–454.
- Miller, G.S., Jr. and Gidley, J.W. 1918. Synopsis of the supergeneric groups of rodents. Journal of the Washington Academy of Sciences 8:431–448.
- Musser, G.G. and Carleton, M.D. 2005. Superfamily Muroidea. Pp. 894–1531 in Wilson, D.E. and Reeder, D.M. (eds.). Mammal Species of the World: a taxonomic and geographic reference. 3rd ed. Baltimore: The Johns Hopkins University Press, 2 vols., 2142 pp. ISBN 978-0-8018-8221-0
- Osgood, W.H. 1933. Two new rodents from Argentina. Fieldiana Zoology 20(3):11–14.
- Patterson, B. 1934. Trachytherus, a typotherid from the Deseado beds of Patagonia. Field Museum of Natural History, Geological Series 6:91–111.
- Patton, J.L., da Silva, M.N.F. and Malcolm, J.R. 2000. Mammals of the Rio Juruá and the evolutionary and ecological diversification of Amazonia. Bulletin of the American Museum of Natural History 244:1–306.
- Reguero, M.A., Dozo, M.T. and Cerdeño, E. 2007. A poorly known rodentlike mammal (Pachyrukhinae, Hegetotheriidae, Notoungulata) from the Deseadan (Late Oligocene) of Argentina. Paleoecology, biogeography, and radiation of the rodentlike ungulates in South America. Journal of Paleontology 81(6):1301–1307.
- Steppan, S.J. 1995. Revision of the tribe Phyllotini (Rodentia: Sigmodontinae), with a phylogenetic hypothesis for the Sigmodontinae. Fieldiana Zoology 80:1–112.
- Tate, G.H.H. 1951. The rodents of Australia and New Guinea. Bulletin of the American Museum of Natural History 97:187–430.
- Voss, R.S. 1988. Systematics and ecology of ichthyomyine rodents (Muroidea): patterns of morphological evolution in a small adaptive radiation. Bulletin of the American Museum of Natural History 188:259–493.
- Voss, R.S. 1992. A revision of the South American species of Sigmodon (Mammalia: Muridae) with notes on their natural history and biogeography. American Museum Novitates 3050:1–56.
- Weksler, M. 2006. Phylogenetic relationships of oryzomyine rodents (Muroidea: Sigmodontinae): separate and combined analyses of morphological and molecular data. Bulletin of the American Museum of Natural History 296:1–149.
- Weksler, M., Percequillo, A.R. and Voss, R.S. 2006. Ten new genera of oryzomyine rodents (Cricetidae: Sigmodontinae). American Museum Novitates 3537:1–29.
- Wood, A.E. 1935. Evolution and relationships of the heteromyid rodents with new forms from the Tertiary of western North America. Annals of Carnegie Museum 24:73–262.