Oryzomys albiventer
Encyclopedia
Oryzomys albiventer is a rodent
in the genus Oryzomys
of family Cricetidae
from interior western Mexico
, in the states of Jalisco
, Guanajuato
, and Michoacán
. First described in 1901 as a separate species, it was later lumped under O. couesi and the marsh rice rat
(O. palustris) until it was reinstated as a species in 2009. It differs from neighboring Oryzomys populations in size and measurements and is a large, brightly colored species with a long tail and robust skull and molars. Its range has been much impacted by agricultural development, but isolated populations are thought to persist.
in 1901 on the basis of ten specimens from Ameca
, Jalisco
. He named the animal albiventer after the white color of its underparts and considered it most closely related to Oryzomys aquaticus (currently included in Oryzomys couesi). Two years later, D.G. Eliot described Oryzomys molestus on the basis of a single individual from Ocotlán, Jalisco; the name molestus means "troublesome, irksome". Eliot considered Oryzomys fulgens, another current synonym
of O. couesi, as the closest relative of his new species. In his 1918 review of North American Oryzomys
, E.A. Goldman assessed the holotype
of O. molestus, an old male, as merely a large example of albiventer, and reduced albiventer to one of many subspecies
of O. couesi. He considered it closely related to three other highland Mexican forms. In 1960, E.R. Hall argued that O. couesi was the same species as the marsh rice rat
(O. palustris) of the United States, and listed albiventer as a subspecies of the latter. Later, O. couesi was again accepted as separate from the marsh rice rat, but O. albiventer was still classified under O. couesi.
In a 2009 revision of the Oryzomys of western Mexico, M.D. Carleton and J. Arroyo-Cabrales noted substantial differences in coloration and measurements between highland populations (albiventer) and lowland populations (mexicanus) in Jalisco. On the basis of these differences, they recognized O. albiventer as a species separate from the lowland populations, which they classified under O. couesi. They confirmed that Eliot's molestus was based on a large example of O. abiventer, but left the status of the three forms Goldman had associated with albiventer—crinitus, aztecus, and regillus—open, noting that there was no convincing evidence that these represented the same species as O. albiventer. The identity and exact provenance of fulgens (supposed to be from the Valley of Mexico
), and consequently its relationship to O. albiventer, remain unknown.
O. albiventer is part of the genus Oryzomys
, which currently includes about eight species distributed from the eastern United States (O. palustris) into northwestern South America (O. gorgasi
). O. albiventer is further part of the O. couesi section, which is centered around the widespread Central American O. couesi and also includes various other species with more limited and peripheral distributions. Many aspects of the systematics
of the O. couesi section remain unclear and it is likely that the current classification underestimates the true diversity of the group. Oryzomys previously included many other species, which were progressively removed in various studies culminating in a contribution by Marcelo Weksler and coworkers in 2006 that removed more than forty species from the genus. All are classified in the tribe Oryzomyini
("rice rats"), a diverse assemblage of American rodents of over a hundred species, and on higher taxonomic levels in the subfamily Sigmodontinae
of family Cricetidae
, along with hundreds of other species of mainly small rodents.
In 1904, Eliot used the common name
"White-bellied Rice Rat" for O. albiventer and "Ocotlan Rice Rat" for O. molestus. In 1918, Goldman also used "White-bellied Rice Rat" for O. albiventer.
are relatively robust. O. albiventer has broad zygomatic arch
es (cheekbones), long incisive foramina
(perforations of the palate
between the incisor
s and the molars), and long nasal bone
s that extend behind the premaxillary bones. Compared to its lowland relative O. couesi mexicanus, O. albiventer is larger and more brightly colored and has larger molars but narrower incisive foramina.
In twelve specimens, total length is 245 to 314 mm (9.6 to 12.4 in), averaging 285.4 mm (11.24 in); head and body length is 116 to 142 mm (4.6 to 5.6 in), averaging 130.0 mm (5.12 in); tail length is 129 to 173 mm (5.1 to 6.8 in), averaging 155.4 mm (6.12 in); hindfoot length is 33 to 40 mm (1.3 to 1.6 in), averaging 36.1 mm (1.42 in); and skull length (occipitonasal length) is 30.0 to 34.5 mm (1.18 to 1.36 in), averaging 32.9 mm (1.30 in).
, southern Guanajuato
, and central and eastern Jalisco
, mostly in the area around Lake Chapala
. Its range has seen massive agricultural development and although populations may survive, the current distribution of the species is certainly highly fragmented. More survey work is needed to assess the distribution and status of O. albiventer.
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....
in the genus Oryzomys
Oryzomys
Oryzomys is a genus of semiaquatic rodents in the tribe Oryzomyini living in southern North America and far northern South America. It includes eight species, two of which—the marsh rice rat of the United States and O. couesi of Mexico and Central America—are widespread; the six others have...
of family Cricetidae
Cricetidae
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...
from interior western Mexico
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
, in the states of Jalisco
Jalisco
Jalisco officially Estado Libre y Soberano de Jalisco is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is located in Western Mexico and divided in 125 municipalities and its capital city is Guadalajara.It is one of the more important states...
, Guanajuato
Guanajuato
Guanajuato officially Estado Libre y Soberano de Guanajuato is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is divided in 46 municipalities and its capital city is Guanajuato....
, and Michoacán
Michoacán
Michoacán officially Estado Libre y Soberano de Michoacán de Ocampo is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is divided in 113 municipalities and its capital city is Morelia...
. First described in 1901 as a separate species, it was later lumped under O. couesi and the marsh rice rat
Marsh Rice Rat
The marsh rice rat is a semiaquatic North American rodent in the family Cricetidae. It is found mostly in the eastern and southern United States, from New Jersey and Kansas south to Florida and northeasternmost Tamaulipas, Mexico; its range previously extended further west and north, where it may...
(O. palustris) until it was reinstated as a species in 2009. It differs from neighboring Oryzomys populations in size and measurements and is a large, brightly colored species with a long tail and robust skull and molars. Its range has been much impacted by agricultural development, but isolated populations are thought to persist.
Taxonomy
Oryzomys albiventer was first described by C.H. MerriamClinton Hart Merriam
Clinton Hart Merriam was an American zoologist, ornithologist, entomologist and ethnographer.Known as "Hart" to his friends, Dr. Clinton Hart Merriam was born in New York City in 1855. His father, Clinton Levi Merriam, was a U.S. congressman. He studied biology and anatomy at Yale University and...
in 1901 on the basis of ten specimens from Ameca
Ameca, Jalisco
Ameca is a city and municipality, in Jalisco in central-western Mexico. The municipality covers an area of 685.73 km². The city is bisected by the Ameca River which drains to the Pacific Ocean near Puerto Vallarta....
, Jalisco
Jalisco
Jalisco officially Estado Libre y Soberano de Jalisco is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is located in Western Mexico and divided in 125 municipalities and its capital city is Guadalajara.It is one of the more important states...
. He named the animal albiventer after the white color of its underparts and considered it most closely related to Oryzomys aquaticus (currently included in Oryzomys couesi). Two years later, D.G. Eliot described Oryzomys molestus on the basis of a single individual from Ocotlán, Jalisco; the name molestus means "troublesome, irksome". Eliot considered Oryzomys fulgens, another current synonym
Synonym (taxonomy)
In scientific nomenclature, a synonym is a scientific name that is or was used for a taxon of organisms that also goes by a different scientific name. For example, Linnaeus was the first to give a scientific name to the Norway spruce, which he called Pinus abies...
of O. couesi, as the closest relative of his new species. In his 1918 review of North American Oryzomys
Oryzomys
Oryzomys is a genus of semiaquatic rodents in the tribe Oryzomyini living in southern North America and far northern South America. It includes eight species, two of which—the marsh rice rat of the United States and O. couesi of Mexico and Central America—are widespread; the six others have...
, E.A. Goldman assessed the holotype
Holotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
of O. molestus, an old male, as merely a large example of albiventer, and reduced albiventer to one of many subspecies
Subspecies
Subspecies in biological classification, is either a taxonomic rank subordinate to species, ora taxonomic unit in that rank . A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one...
of O. couesi. He considered it closely related to three other highland Mexican forms. In 1960, E.R. Hall argued that O. couesi was the same species as the marsh rice rat
Marsh Rice Rat
The marsh rice rat is a semiaquatic North American rodent in the family Cricetidae. It is found mostly in the eastern and southern United States, from New Jersey and Kansas south to Florida and northeasternmost Tamaulipas, Mexico; its range previously extended further west and north, where it may...
(O. palustris) of the United States, and listed albiventer as a subspecies of the latter. Later, O. couesi was again accepted as separate from the marsh rice rat, but O. albiventer was still classified under O. couesi.
In a 2009 revision of the Oryzomys of western Mexico, M.D. Carleton and J. Arroyo-Cabrales noted substantial differences in coloration and measurements between highland populations (albiventer) and lowland populations (mexicanus) in Jalisco. On the basis of these differences, they recognized O. albiventer as a species separate from the lowland populations, which they classified under O. couesi. They confirmed that Eliot's molestus was based on a large example of O. abiventer, but left the status of the three forms Goldman had associated with albiventer—crinitus, aztecus, and regillus—open, noting that there was no convincing evidence that these represented the same species as O. albiventer. The identity and exact provenance of fulgens (supposed to be from the Valley of Mexico
Valley of Mexico
The Valley of Mexico is a highlands plateau in central Mexico roughly coterminous with the present-day Distrito Federal and the eastern half of the State of Mexico. Surrounded by mountains and volcanoes, the Valley of Mexico was a centre for several pre-Columbian civilizations, including...
), and consequently its relationship to O. albiventer, remain unknown.
O. albiventer is part of the genus Oryzomys
Oryzomys
Oryzomys is a genus of semiaquatic rodents in the tribe Oryzomyini living in southern North America and far northern South America. It includes eight species, two of which—the marsh rice rat of the United States and O. couesi of Mexico and Central America—are widespread; the six others have...
, which currently includes about eight species distributed from the eastern United States (O. palustris) into northwestern South America (O. gorgasi
Oryzomys gorgasi
Oryzomys gorgasi, also known as Gorgas's Oryzomys or Gorgas's Rice Rat, is a rodent in the genus Oryzomys of family Cricetidae. First collected as a living animal in 1967, it is known from only a few localities, including a freshwater swamp in the lowlands of northwestern Colombia and a mangrove...
). O. albiventer is further part of the O. couesi section, which is centered around the widespread Central American O. couesi and also includes various other species with more limited and peripheral distributions. Many aspects of the systematics
Systematics
Biological systematics is the study of the diversification of terrestrial life, both past and present, and the relationships among living things through time. Relationships are visualized as evolutionary trees...
of the O. couesi section remain unclear and it is likely that the current classification underestimates the true diversity of the group. Oryzomys previously included many other species, which were progressively removed in various studies culminating in a contribution by Marcelo Weksler and coworkers in 2006 that removed more than forty species from the genus. All are classified 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...
("rice rats"), a diverse assemblage of American rodents of over a hundred species, and on higher taxonomic levels in 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...
of family Cricetidae
Cricetidae
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...
, along with hundreds of other species of mainly small rodents.
In 1904, Eliot used the common name
Common name
A common name of a taxon or organism is a name in general use within a community; it is often contrasted with the scientific name for the same organism...
"White-bellied Rice Rat" for O. albiventer and "Ocotlan Rice Rat" for O. molestus. In 1918, Goldman also used "White-bellied Rice Rat" for O. albiventer.
Description
Oryzomys albiventer is a large and long-tailed Oryzomys. The upperparts are brightly ochraceous, becoming grayer toward the front. The hairs on the underparts are pale gray near the bases and white in the outer half, so that the underparts appear pale grayish according to Carleton and Arroyo-Cabrales (not white as claimed by Merriman). The tail is dark above and light below. The skull and molarsMolar (tooth)
Molars are the rearmost and most complicated kind of tooth in most mammals. In many mammals they grind food; hence the Latin name mola, "millstone"....
are relatively robust. O. albiventer has broad 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...
es (cheekbones), long incisive foramina
Incisive foramen
The fossa incisiva is an opening in the bone of the oral hard palate where blood vessels and nerves may pass. There are four of these openings in the incisive fossa.-Formation:...
(perforations of the palate
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 separate. The palate is divided into two parts, the anterior...
between the incisor
Incisor
Incisors are the first kind of tooth in heterodont mammals. They are located in the premaxilla above and mandible below.-Function:...
s and the molars), and long nasal bone
Nasal bone
The nasal bones are two small oblong bones, varying in size and form in different individuals; they are placed side by side at the middle and upper part of the face, and form, by their junction, "the bridge" of the nose.Each has two surfaces and four borders....
s that extend behind the premaxillary bones. Compared to its lowland relative O. couesi mexicanus, O. albiventer is larger and more brightly colored and has larger molars but narrower incisive foramina.
In twelve specimens, total length is 245 to 314 mm (9.6 to 12.4 in), averaging 285.4 mm (11.24 in); head and body length is 116 to 142 mm (4.6 to 5.6 in), averaging 130.0 mm (5.12 in); tail length is 129 to 173 mm (5.1 to 6.8 in), averaging 155.4 mm (6.12 in); hindfoot length is 33 to 40 mm (1.3 to 1.6 in), averaging 36.1 mm (1.42 in); and skull length (occipitonasal length) is 30.0 to 34.5 mm (1.18 to 1.36 in), averaging 32.9 mm (1.30 in).
Distribution and conservation
O. albiventer occurs at about 1200 to 1800 m (3900 to 5900 ft) elevation in northern MichoacánMichoacán
Michoacán officially Estado Libre y Soberano de Michoacán de Ocampo is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is divided in 113 municipalities and its capital city is Morelia...
, southern Guanajuato
Guanajuato
Guanajuato officially Estado Libre y Soberano de Guanajuato is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is divided in 46 municipalities and its capital city is Guanajuato....
, and central and eastern Jalisco
Jalisco
Jalisco officially Estado Libre y Soberano de Jalisco is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is located in Western Mexico and divided in 125 municipalities and its capital city is Guadalajara.It is one of the more important states...
, mostly in the area around Lake Chapala
Lake Chapala
Lake Chapala is Mexico's largest freshwater lake. It lies in the municipalities of Chapala, Jocotepec , Poncitlán, and Jamay, in Jalisco, and in Venustiano Carranza and Cojumatlán de Régules, in Michoacán.- Geographic Features :...
. Its range has seen massive agricultural development and although populations may survive, the current distribution of the species is certainly highly fragmented. More survey work is needed to assess the distribution and status of O. albiventer.
Literature cited
- Carleton, M.D. and Arroyo-Cabrales, J. 2009. Review of the Oryzomys couesi complex (Rodentia: Cricetidae: Sigmodontinae) in western Mexico. Bulletin of the American Museum of Natural History 331:94–127.
- Eliot, D.G. 1903. A list of a collection of Mexican mammals with descriptions of some apparently new forms. Field Columbian Museum, Zoological Series 3(8):141–149.
- Eliot, D.G. 1904. The land and sea mammals of Middle America and the West Indies. Field Columbian Museum, Zoölogical Series 4(1):i–xxi, 1–439.
- Goldman, E.A. 1918. The rice rats of North America. North American Fauna 43:1–100.
- Hall, E.R. 1960. Oryzomys couesi only subspecifically different from the marsh rice rat, Oryzomys palustris (subscription required). The Southwestern Naturalist 5(3):171–173.
- Merriam, C.H. 1901. Synopsis of the rice rats (genus Oryzomys) of the United States and Mexico. Proceedings of the Washington Academy of Sciences 3:273–295.
- 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
- 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.