anatomy Anatomy () is the branch of morphology concerned with the study of the internal structure of organisms and their parts. Anatomy is a branch of natural science that deals with the structural organization of living things. It is an old scien ...

, posterolateral palatal pits are gaps at the sides of the back of the bony

palate The palate () is the roof of the mouth in humans and other mammals. It separates the oral cavity from the nasal cavity. A similar structure is found in crocodilians, but in most other tetrapods, the oral and nasal cavities are not truly sep ...

, near the last

molars The molars or molar teeth are large, flat tooth, teeth at the back of the mouth. They are more developed in mammal, mammals. They are used primarily to comminution, grind food during mastication, chewing. The name ''molar'' derives from Latin, '' ...

.Weksler, 2006, p. 34 Posterolateral palatal pits are present, in various degrees of development, in several members of the

rodent Rodents (from Latin , 'to gnaw') are mammals of the Order (biology), order Rodentia ( ), which are characterized by a single pair of continuously growing incisors in each of the upper and Mandible, lower jaws. About 40% of all mammal specie ...

family

Cricetidae The Cricetidae are a family of rodents in the large and complex superfamily Muroidea. It includes true hamsters, voles, lemmings, muskrats, and New World rats and mice. At over 870 species, it is either the largest or second-largest family ...

. Many members of the family lack them or have only simple pits, but

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 (comprising the hamsters and New World rats and mice). Some authorities plac ...

(voles, lemmings, and relatives) and

Oryzomyini Oryzomyini is a tribe of rodents in the subfamily Sigmodontinae of the family Cricetidae. It includes about 120 species in about thirty genera,Weksler et al., 2006, table 1 distributed from the eastern United States to the southernmost parts of S ...

(rice rats and relatives) have more highly developed posterolateral palatal pits. Posterolateral palatal pits are also present in some other rodents, including ''

Glis Glis is an electronic music project founded in 2001 by Shaun Frandsen of Seattle, WA. The band has experienced several lineup changes and guest appearances, with frontman Shaun Frandsen acting as primary producer, vocalist, songwriter, and inst ...

'', ''

Jaculus The jaculus (or iaculus, pl. ''jaculi'', meaning "thrown" in Latin) is a small mythical serpent or dragon. It can be shown with wings and sometimes has front legs. It is also sometimes known as the javelin snake. In Greek mythology It was said ...

'', '' Hystrix'', ''

Abrocoma ''Abrocoma'' is a genus of Abrocomidae, abrocomid rodents found in the Andes of South America, from southern Peru to central Chile. The genus contains eight species, most of which are found in isolated mountain ranges in northwestern Argentina. T ...

'', '' Ctenomys'', ''

Chinchilla Chinchilla refers to either of two species ('' Chinchilla chinchilla'' and '' Chinchilla lanigera'') of crepuscular rodents of the parvorder Caviomorpha, and are native to the Andes mountains in South America. They live in colonies called "her ...

'', and ''

Lagidium ''Lagidium'' is a genus of rodents in the family Chinchillidae. Taxonomy Prior to 2009, most authors considered there to be three species of mountain viscachas. However, taxonomy sometimes differs by authors (e.g. ''L. peruanum'' is included wit ...

''.

Sigmodontinae

Many members of the mainly South American cricetid subfamily

Sigmodontinae The rodent subfamily Sigmodontinae 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 ...

have posterolateral palatal pits. In

(rice rats), the largest

tribe The term tribe is used in many different contexts to refer to a category of human social group. The predominant worldwide use of the term in English is in the discipline of anthropology. The definition is contested, in part due to conflict ...

of the Sigmodontinae, all but some species—''

Mindomys hammondi ''Mindomys'' is a genus of sigmodontine rodents in the family Cricetidae. It includes two species known only from Ecuador, Hammond's rice rat (''Mindomys hammondi'') and the Kutukú rat (''Mindomys kutuku''). See also * List of mammals of Ecu ...

'' and ''

Sigmodontomys aphrastus ''Tanyuromys aphrastus'', known as the long-tailed sigmodontomys, Harris's rice water rat, or the long-tailed rice rat, is a species of rodent in the family Cricetidae. It is known from Costa Rica, Panama, and Ecuador. In 2012, it was reassigned ...

'' usually have only one small pit on each side of the palate—have prominent posterolateral palatal pits, often more than one on each side of the palate. In many oryzomyines, the pits are located in a deep depression or fossa. This depression has been termed the "palatal fossa" in the genus ''

Cerradomys ''Cerradomys'' is a genus of oryzomyine rodents from eastern Bolivia, Paraguay, and central Brazil found in cerrado, Caatinga and Gran Chaco habitats. The species in this genus have historically been placed in ''Oryzomys'', but according to cla ...

''; its varying depth serves as a diagnostic character separating some of the species. The presence of complex posterolateral palatal pits is a

synapomorphy In phylogenetics, an apomorphy (or derived trait) is a novel Phenotypic trait, character or character state that has evolution, evolved from its ancestral form (or Plesiomorphy and symplesiomorphy, plesiomorphy). A synapomorphy is an apomorphy sh ...

either of Oryzomyini or of Oryzomyini minus ''Mindomys''. Members of the genus ''

Nephelomys ''Nephelomys'' is a genus of South American oryzomyine rodents found in the Andes from Bolivia to Venezuela, with a westward extension into the mountains of Costa Rica. Its generic name is derived from the Ancient Greek word ''nephelê'' "mist", ...

'' usually have complex posterolateral palatal pits, recessed into deep fossae, but '' N. caracolus'' and '' N. nimbosus'' have simpler pits. One of the putative subdivisions within Oryzomyini, Clade D, has posterolateral palatal pits recessed into a fossa as one of its synapomorphies, although the feature is reversed in several subgroups. The extinct island endemic '' Noronhomys vespuccii'' also had smaller pits, perhaps because of its short palate. Among members of the tribe

Thomasomyini The rodent subfamily Sigmodontinae 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 c ...

, posterolateral palatal pits are small or absent. ''Aepeomys'' lacks them, but '' Rhagomys longilingua'' does have posterolateral palatal pits. The possible thomasomyine '' Abrawayaomys chebezi'' has small posterolateral palatal pits. Members of the

Phyllotini The rodent subfamily Sigmodontinae 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 c ...

tribe always have posterolateral palatal pits. In some species, they are displaced to the back from their usual position just before the mesopterygoid fossa into the fossa. The condition of the pits has been used to separate species of ''

Phyllotis ''Phyllotis'' is a genus of rodent in the family Cricetidae. These mice are commonly confused with ''Auliscomys, Graomys'' and ''Loxodontomys.'' ''.'' In order to tell these genera apart, one must look at the tail. Species in the genus ''Phyllo ...

''. The tribe

Ichthyomyini Ichthyomyini is a tribe of New World rats and mice in the subfamily Sigmodontinae. The species within this tribe share the characteristics of all being carnivorous semiaquatic rodents. The following genera are recognized in this tribe: * Subtribe ...

is characterized by inconspicuous posterolateral palatal pits.

Arvicolinae

, a group that includes the

vole Voles are small rodents that are relatives of lemmings and hamsters, but with a stouter body; a longer, hairy tail; a slightly rounder head; smaller eyes and ears; and differently formed molars (high-crowned with angular cusps instead of lo ...

s and

lemming A lemming is a small rodent, usually found in or near the Arctic in tundra biomes. Lemmings form the subfamily Arvicolinae (also known as Microtinae) together with voles and muskrats, which form part of the superfamily Muroidea, which also inclu ...

s, usually have posterolateral palatal pits, but the configuration of the pits is variable. In some species, the pits do not extend to the ventral face of the palate.

Neotominae

Posterolateral palatal pits are poorly developed or absent in many members of the mostly North American subfamily

Neotominae The Neotominae are a subfamily of the family Cricetidae. They consist 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, packrats, and grasshopp ...

, including ''

Peromyscus ''Peromyscus'' is a genus of rodents. They are commonly referred to as deer mice or deermice, not to be confused with the chevrotain or "mouse deer". They are New World mice only distantly related to the common house and laboratory mouse, ''M ...

'' (deer mice) and related genera.

Cladistics

The presence and development of posterolateral palatal pits has been used as a character in

cladistic Cladistics ( ; from Ancient Greek 'branch') is an approach to biological classification in which organisms are categorized in groups ("clades") based on hypotheses of most recent common ancestry. The evidence for hypothesized relationships is ...

analyses of oryzomyines by Weksler (2006), Carleton and Olson (1999), and Carleton and Musser (1989); neotomines by Carleton (1980); and phyllotines by Steppan (1995).Steppan, 1995, p. 39

References

Literature cited

* *Carleton, M.D. 1989. Systematics and evolution. Pp. 7–141 in Kirkland, G.L. and Layne, J.N. (eds.). Advances in the study of ''Peromyscus'' (Rodentia). Lubbock: Texas Tech University Press. * * * * * * * *Luna, L. and Patterson, B.D. 2003. A remarkable new mouse (Muridae: Sigmodontinae) from southeastern Peru: with comments on the affinities of ''Rhagomys rufescens'' (Thomas, 1886). Fieldiana Zoology 101:1–24. *Pardiñas, U.F.J., Teta, P. and D'Elía, G. 2009. Taxonomy and distribution of ''Abrawayaomys'' (Rodentia: Cricetidae), an Atlantic Forest endemic with the description of a new species. Zootaxa 2128:39–60. * *Steppan, S.J. 1995. Revision of the tribe Phyllotini (Rodentia: Sigmodontinae), with a phylogenetic hypothesis for the Sigmodontinae. Fieldiana Zoology 80:1–112. * * * * * *{{cite journal , doi=10.1206/0003-0082(2006)3537 :TNGOOR.0.CO;2 , hdl=2246/5815 , year=2006 , issue=3537 , pages=1 , title=Ten New Genera of Oryzomyine Rodents (Cricetidae: Sigmodontinae) , last1=Weksler , first1=Marcelo , last2=Percequillo , first2=Alexandre Reis , last3=Voss , first3=Robert S. , journal=American Museum Novitates, s2cid=84088556 , url=https://zenodo.org/record/5385275 , hdl-access=free Rodent anatomy