|Skull of Transandinomys bolivaris from Cerro Azul, Panama, seen from above|
|Genus:|| Transandinomys |
Weksler, Percequillo, and Voss, 2006
| Oryzomys talamancae |
J.A. Allen, 1891
|Distribution of Transandinomys bolivaris (top) and T. talamancae (bottom) in Central America and northwestern South America.|
Transandinomys is a genus of rodents in the tribe Oryzomyini of family Cricetidae. It includes two species— T. bolivaris and T. talamancae —found in forests from Honduras in Central America south and east to southwestern Ecuador and northwestern Venezuela in northern South America. Until 2006, its members were included in the genus Oryzomys , but phylogenetic analysis showed that they are not closely related to the type species of that genus, and they have therefore been placed in a new genus. They may be most closely related to genera like Hylaeamys and Euryoryzomys , which contain very similar species. Both species of Transandinomys have had eventful taxonomic histories.
Transandinomys bolivaris and T. talamancae are medium-sized, soft-furred rice rats. The upperparts—brownish in T. bolivaris and reddish in T. talamancae—are much darker than the whitish underparts. Both species are characterized by very long vibrissae (whiskers), but those of T. bolivaris are particularly long. In addition to whisker length and fur color, several other morphological differences distinguish the two, including the wider first upper molar in T. bolivaris. Species of Hylaeamys and Euryoryzomys also differ from Transandinomys in some details of the skull and teeth and have shorter whiskers. Species of Transandinomys live on the ground, are active during the night, eat both plant and animal matter, and construct nests of vegetation. Both are hosts to various external parasites. They are in no apparent danger of extinction and have been assessed as "Least Concern" in the IUCN Red List.
The first species of Transandinomys to be scientifically described was T. talamancae , named as Oryzomys talamancae by Joel A Allen in 1891. Several other species were soon added to the genus Oryzomys , then more broadly defined than currently, that are now classified in Transandinomys, including Oryzomys bolivaris (now Transandinomys bolivaris ) by Allen in 1901. In his 1918 review of North American Oryzomys, Edward Alphonso Goldman placed Oryzomys talamancae and Oryzomys bombycinus (=T. bolivaris) each in their own group, but thought them closely related. In 1960, O. talamancae was synonymized with "Oryzomys capito" (= Hylaeamys megacephalus ), but it has again been recognized as a separate species since 1983. The species was reviewed by Guy Musser and Marina Williams in 1985 and again by Musser and colleagues in 1998, who documented the diagnostic characters of the species, its synonyms, and its distribution. The 1998 study by Musser and colleagues also documented Oryzomys bolivaris as the correct name for the species previously known as Oryzomys bombycinus and reviewed that species.
In 2006, Marcelo Weksler published a broad phylogenetic analysis of Oryzomyini, the tribe to which Oryzomys and related genera belong, using morphological data and DNA sequences from the IRBP gene. O. talamancae appeared within "clade B", together with other species formerly associated with Oryzomys capito. Some analyses placed it closest to species now placed in Euryoryzomys or Nephelomys , but with low support. O. bolivaris was not included. Species of Oryzomys included in Weksler's study did not cluster together in his results, but instead appeared dispersed across Oryzomyini, indicating that the genus was polyphyletic and should be split up. Later in the same year, Weksler, Alexandre Percequillo, and Robert Voss introduced ten new genera of Oryzomyini formerly placed in Oryzomys, including Transandinomys for Oryzomys talamancae and O. bolivaris, with the former as the type species. Transandinomys is now one of about thirty genera within Oryzomyini, a diverse group of well over a hundred species. Oryzomyini is one of several tribes within the subfamily Sigmodontinae of the family Cricetidae, which includes hundreds of other species of mainly small rodents, distributed chiefly in Eurasia and the Americas.
Transandinomys species are medium-sized, soft-furred rice rats. alfaroi.They closely resemble other medium-sized lowland forest rice-rats, such as Hylaeamys and Euryoryzomys from the Amazon rainforest and surrounding areas and Handleyomys alfaroi from Central America and northwestern South America. In general, Transandinomys are distinguished from those animals by their very long superciliary vibrissae (whiskers above the eyes). Euryoryzomys species are in general slightly larger and Hylaeamys are as large as Transandinomys, so that the only feature of external morphology that distinguishes the two genera is the length of the vibrissae. Handleyomys alfaroi is smaller than both species of Transandinomys, but juvenile Transandinomys may be confused with similarly colored adult H.
The fur is brownish (T. bolivaris) or reddish (T. talamancae) above and lighter below, appearing whitish, but the hairs on the underparts have gray bases. The snout is large. The mystacial (above the mouth) and superciliary vibrissae both extend to at least the back margin of the ears when laid back against the head, but are much longer in T. bolivaris. The pinna (external ear) is large. On the hindfeet, which are long and narrow, ungual tufts of hairs surround the bases of the toes. In T. bolivaris, the sole usually entirely lacks squamae (small, scale-like structures), but T. talamancae does have squamae on part of its sole. The claw of the first toe extends about to the middle of the first phalange of the second and that of the fifth toe extends nearly to the base of the second phalange of the fourth. The tail is at least about as long as the head and body, sometimes slightly longer. The tail is darker above than below in T. talamancae, but there may not be a difference in color in T. bolivaris. The tail appears naked, but is covered with fine hairs.
Females have four pairs of mammae, as usual in oryzomyines. bolivaris has 58 chromosomes and the number of chromosomal arms (fundamental number) is 80 (2n = 58, FN = 80). Studies in Ecuador and Venezuela have recorded several different karyotypes in T. talamancae, with the number of chromosomes ranging from 34 to 54 and the fundamental number from 60 to 67.Like most rice rats, Transandinomys species have twelve thoracic (chest) and seven lumbar vertebrae. According to a study in Costa Rica, T.
|Species||Head and body||Tail||Hindfoot||Ear||Mass|
|Measurements are in millimeters, except mass in grams.|
In the skull, the rostrum (front part) is long. The nasal bones are short, with their back margin not extending beyond the lacrimal bones, which are in contact with both the maxillary and frontal bones. The zygomatic notch is moderately developed and the jugal bone is small, so that when seen from the side the maxillary and squamosal parts of the zygomatic arch (cheekbone) overlap. Usually, the suture (line of fusion) between the frontal and the squamosal is continuous with that between the frontal and the parietal bone. In T. talamancae, the parietals usually extend from the roof of the braincase broadly on to the sides, but in T. bolivaris they are more commonly restricted to the roof.
The incisive foramina (openings in the front part of the palate) are short, not extending between the first molars. The posterolateral palatal pits (small openings at the back of the palate, near the third molars) are poorly developed. The mesopterygoid fossa, the gap behind the back margin of the palate, does not usually reach forward between the maxillaries. Its roof either is wholly ossified or contains small sphenopalatine vacuities. Unlike in some other oryzomyines, the buccinator-masticatory foramen and the foramen ovale accessorium, two foramina (openings) in the skull, are not separated by an alisphenoid strut. The pattern of grooves and foramina in the skull indicates that the circulation of the arteries of the head follows the primitive pattern, as in most similar species but unlike in Hylaeamys . Usually, the mastoid bone contains small openings (fenestrations) in T. talamancae, but not in T. bolivaris. In the mandible (lower jaw), the capsular process (a process at the root of the incisor) is weak to absent and the upper and lower masseteric ridges, which anchor some of the chewing muscles, do not join into a single crest and reach their front margin below the first molar.
The upper incisor is opisthodont, with the cutting edge oriented backward. As usual in oryzomyines, the molars are brachydont (low-crowned). talamancae than in T. bolivaris. Unlike in many other rice rats, including Handleyomys alfaroi and Euryoryzomys species, the mesoflexus on the second upper molar, which separates the paracone (one of the main cusps) from the mesoloph (an accessory crest), is not divided in two by an enamel bridge. On the upper third molar, the hypoflexus (which in oryzomyines ranges from a slight indentation on the lingual, or inner, side of the tooth to a conspicuous valley between the main cusps) is more developed in Euryoryzomys than in Transandinomys. The hypoflexid on the second lower molar, the main valley between the cusps, extends more than halfway across the crown; it is much shorter in H. alfaroi, Euryoryzomys, and Hylaeamys yunganus . Each of the upper molars has three roots (two at the labial, or outer, side and one at the lingual, or inner, side) and each of the lowers has two (one at the front and one at the back); both species of Transandinomys lack the additional small roots that are present in various other oryzomyines, including species of Euryoryzomys, Nephelomys, and Handleyomys.The first upper molar is narrower in T.
The distribution of Transandinomys extends from eastern Honduras through Nicaragua, Costa Rica, Panama, and Colombia south and east to southwestern Ecuador and northern Venezuela, generally west and north of the Andes. bolivaris occurs from Honduras mainly on the Caribbean side of Central America south to western Colombia and northwestern Ecuador, up to 1800 m (5900 ft) above sea level. T. talamancae, which is found up to 1525 m (5000 ft) above sea level, is less widely distributed in Central America, as it is not known further north than northwestern Costa Rica, but is more widely distributed in South America, occurring into far southwestern Ecuador and northern Venezuela. It has also been recorded south of the Venezuelan Andes, in the narrow strip of forest between the Llanos and the mountains. Both species are forest rats, but whereas T. bolivaris is restricted to humid forest formations, T. talamancae apparently is more tolerant of drier forest, which explains its wider South American distribution.The ranges of the two species overlap, but are distinct. T.
Both species live on the ground, are active during the night, are solitary, and feed mainly on fruits and seeds, but may also eat herbs and insects. They build nests of leaves and branches among vegetation, for example in a tree hollow, or under rocks. talamancae breeds throughout the year and the average litter size is about six. Various species of mites, chiggers, fleas, and sucking lice have been recorded as parasites on both species.In Panama, T.
Transandinomys talamancae is common or even abundant, but T. bolivaris generally occurs less frequently. Because both species are widespread, presumably have large populations, and occur in numerous protected areas, they are assessed as "Least Concern" by the IUCN Red List; deforestation is noted as a possible threat to T. bolivaris, but T. talamancae is said to lack major threats.
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 (O. palustris) of the United States and O. couesi of Mexico and Central America—are widespread; the six others have more restricted distributions. The species have had eventful taxonomic histories, and most species were at one time included in the marsh rice rat; additional species may be recognized in the future. The name Oryzomys was established in 1857 by Spencer Fullerton Baird for the marsh rice rat and was soon applied to over a hundred species of American rodents. Subsequently, the genus gradually became more narrowly defined until its current contents were established in 2006, when ten new genera were established for species previously placed in Oryzomys.
Euryoryzomys emmonsae, also known as Emmons' rice rat or Emmons' oryzomys, is a rodent from the Amazon rainforest of Brazil in the genus Euryoryzomys of the family Cricetidae. Initially misidentified as E. macconnelli or E. nitidus, it was formally described in 1998. A rainforest species, it may be scansorial, climbing but also spending time on the ground. It lives only in a limited area south of the Amazon River in the state of Pará, a distribution that is apparently unique among the muroid rodents of the region.
Hylaeamys laticeps, also known as the Atlantic Forest oryzomys or the large-headed rice rat, is a species of rodent in the genus Hylaeamys of family Cricetidae.
Hylaeamys perenensis, formerly Oryzomys perenensis, also known as the western Amazonian oryzomys, is an oryzomyine rodent of the family Cricetidae.
Handleyomys fuscatus, also known as the dusky-footed Handley's mouse or dusky-footed montane mouse, is a species of rodent in the tribe Oryzomyini of family Cricetidae. It was previously placed in the genus Aepeomys, but it is closely similar to Handleyomys intectus, and accordingly both species were placed in the new genus Handleyomys in 2002. It is found only in Colombia.
Nephelomys albigularis, also known as the white-throated oryzomys or Tomes's rice rat, is a species of rodent in the genus Nephelomys of family Cricetidae. Described in 1860, it was the first Nephelomys species to be discovered. It was originally described in the defunct genus Hesperomys as Hesperomys albigularis and considered related to the much smaller H. longicaudatus. By 1894, it was placed in Oryzomys, as Oryzomys albigularis, and associated with what is now Nephelomys meridensis. In the early 1960s, the scope of the species was considerably expanded to include most of the species that are now in Nephelomys, as well as a single name, boliviae, that is currently a synonym of Euryoryzomys nitidus. From 1976 on, several of these were reinstated as separate species.
Handleyomys alfaroi, also known as Alfaro's rice rat or Alfaro's oryzomys, is a species of rodent in the genus Handleyomys of family Cricetidae. It is found in Belize, Colombia, Costa Rica, Ecuador, El Salvador, Guatemala, Honduras, Mexico, Nicaragua, and Panama. It was previously included in Oryzomys as Oryzomys alfaroi. Its natural habitats are subtropical and tropical lowland or montane dry forests at elevations ranging from sea level to 2500 m.
Transandinomys bolivaris, also known as the long-whiskered rice rat, is a rodent in the genus Transandinomys. It is found in humid forest from northeastern Honduras to western Ecuador, up to 1,800 m (5,900 ft) above sea level. Since it was first described in 1901 from Ecuador, six scientific names have been introduced for it, but their common identity was not documented until 1998 and the species has long been known under the name Oryzomys bombycinus, described from Panama in 1912. The name Oryzomys bolivaris was used before it was moved to the new genus Transandinomys with Transandinomys talamancae in 2006.
Nephelomys devius, also known as the Talamancan oryzomys, Boquete rice rat, Chiriqui rice rat, or montane rice rat, is a species of rodent in the genus Nephelomys of family Cricetidae. It is found in cloud forest in the highlands of Costa Rica and western Panama.
Aegialomys galapagoensis, also known as the Galápagos rice rat or Galápagos oryzomys, is a species of rodent in the family Cricetidae from the Galápagos Islands.
Mindomys hammondi, also known as Hammond's rice rat or Hammond's oryzomys, is a species of rodent in the tribe Oryzomyini of family Cricetidae. Formerly considered to be related with Nectomys, Sigmodontomys, Megalomys, or Oryzomys, it is now placed in its own genus, Mindomys, but its relationships remain obscure; some evidence supports a placement near Oecomys or as a basal member of Oryzomyini.
Hylaeamys megacephalus, also known as Azara's broad-headed oryzomys or the large-headed rice rat, is a species of rodent in the genus Hylaeamys of family Cricetidae, of which it is the type species. It is found mainly in lowland tropical rainforest from its type locality in Paraguay north through central Brazil, French Guiana, Guyana, Suriname, and Venezuela onto Trinidad and Tobago. To its west and east, other closely related species of Hylaeamys are found: H. perenensis in western Amazonia, H. acritus in Bolivia, and H. laticeps and H. oniscus in the Atlantic Forest of eastern Brazil.
Eremoryzomys polius, also known as the gray rice rat or the Marañon oryzomys, is a rodent species in the tribe Oryzomyini of the family Cricetidae. Discovered in 1912 and first described in 1913 by Wilfred Osgood, it was originally placed in Oryzomys and named Oryzomys polius. In 2006, a cladistic analysis found that it was not closely related to Oryzomys in the strict sense or to any other oryzomyine then known, so that it is now placed in its own genus, Eremoryzomys. The Brazilian genus Drymoreomys, named in 2011, is probably the closest relative of Eremoryzomys. Eremoryzomys has a limited distribution in the dry upper valley of the Marañón River in central Peru, but may yet contain more than one species.
Transandinomys talamancae is a rodent in the genus Transandinomys that occurs from Costa Rica to southwestern Ecuador and northern Venezuela. Its habitat consists of lowland forests up to 1,500 m (5,000 ft) above sea level. With a body mass of 38 to 74 g, it is a medium-sized rice rat. The fur is soft and is reddish to brownish on the upperparts and white to buff on the underparts. The tail is dark brown above and lighter below and the ears and feet are long. The vibrissae (whiskers) are very long. In the skull, the rostrum is long and the braincase is low. The number of chromosomes varies from 34 to 54.
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. It is part of the clade Oryzomyalia, which includes most of the South American Sigmodontinae.
Hylaeamys is a genus of South American oryzomyine rodents found principally in humid forested areas east of the Andes. The species in this genus have historically been placed in Oryzomys. They are most closely related to Euryoryzomys, Transandinomys, Nephelomys, Oecomys, and Handleyomys, and most closely resemble species of the former two genera. They are distinguished from members of Euryoryzomys by all-dark or indistinct two-tone tail coloration, from members of Transandinomys by having shorter whiskers above their eyes that do not extend posteriorly behind their ears, and in both cases by differences in carotid circulation. The genus is named after hylaea, the term used by Humboldt for the lowland South American rainforests that are the main habitat of the genus.
Euryoryzomys is a genus of rodents in the tribe Oryzomyini of family Cricetidae. It includes six species, which are distributed in South America. Until 2006, its members were included in the genus Oryzomys, but they are not closely related to the type species of that genus, and therefore they were placed in a new genus. They are most closely related to genera like Hylaeamys and Transandinomys; many members of these genera were previously placed in a single species, known as Oryzomys capito. The genus name, Euryoryzomys, combines the name "Oryzomys" with the Ancient Greek word eurus "broad", referring to the broad range in distribution of the genus.
Handleyomys is a genus of Central and South American rodents in the tribe Oryzomyini of family Cricetidae. It was first described in 2002 to include two species from the Colombian Andes which were previously included in distinct and unrelated genera, Aepeomys and Oryzomys, but which turned out to be closely related. Later, in 2006, six other species were provisionally added from Oryzomys; these are expected to be placed in new genera in the future.
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", referring to the cloud forest habitat of the members of the genus.
Nephelomys moerex is a species of rodent in the genus Nephelomys of family Cricetidae. The type locality is at Mindo in western Ecuador, where it has been recorded together with three other rodents of the oryzomyine group, Sigmodontomys aphrastus, Mindomys hammondi, and Handleyomys alfaroi, as well as three opossums, Chironectes minimus and unidentified species of Didelphis and Marmosa. Mindo is a "tiny agricultural community" located at 0°02'S, 78°48'W and 1,264 metres (4,150 ft) above sea level. It was originally described by Oldfield Thomas as a subspecies of Oryzomys albigularis. It remained synonymized under this species until it was recognized as a separate species when the genus Nephelomys was established for Oryzomys albigularis and related species in 2006.