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Mindomys hammondi és una espècie de rosegador de la família dels cricètids. És endèmic del nord-oest de l'Equador, on viu a altituds d'entre 1.200 i 2.700 msnm. Els seus hàbitats naturals són els boscos montans subtropicals i les selves nebuloses. Està amenaçat per la destrucció del seu medi.[1] Anteriorment se'l considerava un parent proper de Nectomys, Sigmodontomys, Megalomys o Oryzomys, però actualment se'l classifica en el seu propi gènere, Mindomys. Tanmateix, les seves relacions encara són incertes i alguns indicis el situen prop d'Oecomys o com a membre basal dels orizominis.
Mindomys hammondi és una espècie de rosegador de la família dels cricètids. És endèmic del nord-oest de l'Equador, on viu a altituds d'entre 1.200 i 2.700 msnm. Els seus hàbitats naturals són els boscos montans subtropicals i les selves nebuloses. Està amenaçat per la destrucció del seu medi. Anteriorment se'l considerava un parent proper de Nectomys, Sigmodontomys, Megalomys o Oryzomys, però actualment se'l classifica en el seu propi gènere, Mindomys. Tanmateix, les seves relacions encara són incertes i alguns indicis el situen prop d'Oecomys o com a membre basal dels orizominis.
Mindomys hammondi, also known as Hammond's rice rat[2] or Hammond's oryzomys,[8] is an endangered 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 then genus Mindomys, but its relationships remain obscure; some evidence supports a placement near Oecomys or as a basal member of Oryzomyini.
Mindomys hammondi is known only from Ecuador, where it occurs in montane forest; a record from the Amazon basin lowlands is dubious. Reportedly, it lives on the ground and is associated with water; others suggest it lives in trees. A large, long-tailed, and long-whiskered rat, its fur is buff above and abruptly lighter below. The front part of the skull (rostrum) is heavily built.
The species is named after the collector who first found it, Gilbert Hammond. He supplied natural history specimens to Oldfield Thomas and others.[9]
In 1913, Oldfield Thomas of the British Museum of Natural History (BMNH) in London published the first description of Mindomys hammondi, using two specimens collected at Mindo in Pichincha Province, Ecuador, in the same year by Gilbert Hammond. He named the species Nectomys hammondi, classifying it in the genus Nectomys, which at the time included not only the large water rats currently placed in it, but also Sigmodontomys alfari and Oryzomys dimidiatus. He considered the animal to be most closely related to Nectomys russulus, a species he had himself described in 1897 and which is now recognized as a synonym of Sigmodontomys alfari.[10]
In his 1941 review The Families and Genera of Living Rodents, Sir John Ellerman retained N. hammondi as a species of Nectomys, but noted that the features of its teeth were atypical for the genus, as "the cusps appear to show no tendency to become suppressed."[11] Reviewing the genus Nectomys in 1944, Philip Hershkovitz listed N. hammondi among species of Nectomys incertae sedis (of uncertain position), and considered its placement in Nectomys as dubious. Characters he listed as conflicting with a Nectomys identity of the species included the short hindfoot with a long fifth toe, the weakly developed posterolateral palatal pits (perforations of the palate near the third molars), and the orientation of the zygomatic plate.[12]
Hershkovitz published again on Nectomys in 1948 after examining additional material, including the holotype of N. hammondi. He now considered the latter to be a species of Oryzomys (at the time a large genus that included most of the current members of the tribe Oryzomyini), but distinctive enough to be placed in its own subgenus. Noting that the species was "extremely long-tailed", he introduced the subgeneric name Macruroryzomys for hammondi.[5] He also wrote that Oryzomys aphrastus (currently Sigmodontomys aphrastus), then known only from Costa Rica, may be the closest relative of hammondi.[5]
In his 1962 Ph.D. thesis, Clayton Ray considered O. hammondi to be most closely related to Megalomys, which includes giant rats from the Caribbean, and classified it as a member of the subgenus Megalomys of genus Oryzomys.[13] In 1970, Hershkovitz treated the species in another publication and noted that his name Macruroryzomys was a nomen nudum ("naked name") because he had not explicitly mentioned characters differentiating it from other taxa in his 1948 publication.[14] Nevertheless, he did not do anything to rectify the situation, and Macruroryzomys remains a nomen nudum.[15] Hershkovitz rejected any relationship between O. hammondi and Nectomys or O. aphrastus[16] and instead argued that O. hammondi was closely similar to Megalomys and may be close to the ancestor of Megalomys.[17] In 1982, Steadman and Ray mentioned the animal in passing under the name Macruroryzomys hammondi and reaffirmed its relationship to Megalomys.[18] In the 2005 third edition of Mammal Species of the World, Guy Musser and Michael Carleton listed O. hammondi as an Oryzomys of obscure affinities, but suggested that it may be related to Megalomys.[8]
In 2006, Marcelo Weksler published a large-scale cladistic analysis of Oryzomyini ("rice rats"), the group (tribe) to which hammondi and the related species mentioned above belong. He used both morphological and molecular characters, but had only morphological data for Oryzomys hammondi. The placement of the species in his results was unstable; some trees placed it close to the tree rice rats, Oecomys, within clade B and others placed it as an isolated lineage, basal to all other Oryzomyini.[19]
Traits of O. hammondi that supported the latter placement include: a relatively short palate that does not extend behind the maxillary bones; simple posterolateral palatal pits; absence of a capsular process (a raising of the bone of the mandible, or lower jaw, at the back end of the incisor); and presence of the posteroloph on the upper third molar (a crest at the back of the tooth). In these characters, O. hammondi differs from many or most Oryzomyini and is similar to some species outside Oryzomyini, but all traits of O. hammondi are present in at least one other member of the tribe.[20] Traits shared by O. hammondi and Oecomys included: tail with the same coloration above and below (unicolored); parietal bones extending to the sides of the skull; narrow zygomatic plate, without a zygomatic notch; posteroloph present on upper third molar; mesoflexus (a valley in the molar crown in front of the mesoloph crest) on upper second molar not divided in two.[Note 2][24]
In Weksler's analysis, species placed in Oryzomys did not form a coherent (monophyletic) group, but instead were found at various positions across the oryzomyine tree, and he suggested that most of these species, including O. hammondi, should be placed in new genera.[25] Later in 2006, Weksler and others described ten new genera for species formerly placed in Oryzomys,[26] including Mindomys for hammondi.[7] Noting its "enigmatic distribution" and uncertain but perhaps basal position within Oryzomyini, they labeled the species an "extraordinary rat" worthy of continued inquiry.[15] The generic name refers to Mindo, the type locality of M. hammondi.[15]
Mindomys is now one of about 28 genera[26] in the tribe Oryzomyini, which includes well over a hundred species distributed mainly in South America, including nearby islands such as the Galápagos Islands and some of the Antilles. Oryzomyini is one of several tribes recognized within the subfamily Sigmodontinae, which encompasses hundreds of species found across South America and into southern North America. Sigmodontinae itself is the largest subfamily of the family Cricetidae, other members of which include voles, lemmings, hamsters, and deermice, all mainly from Eurasia and North America.[27]
Mindomys hammondi is a large rice rat;[28] all other rats known within its range are smaller.[29] The fur is relatively short and woolly[30] and is buffy with a grayish tone above and much paler—yellow or white—below, with the bases of the hairs grey.[31] It has a long snout and small, dark ears that appear hairless. The vibrissae (whiskers) are long.[32] The very long tail is dark both above and below[7] and has rectangular scales.[30] The hindfeet are broad, with long, narrow digits.[32] They have poorly developed ungual tufts, patches of hair between the digits and along the plantar margins. The squamae, small structures resembling scales that cover the soles of the hindfeet in many oryzomyines, are indistinct.[33] The fifth digit reaches to about half the length of the second phalange of the fourth.[32] As in most oryzomyines, females have eight mammae.[34] In specimens with published measurements, head and body length is 173 to 203 mm (6.8 to 8.0 in), tail length is 251 mm (9.9 in), hindfoot length is 41 to 42 mm (1.6 to 1.7 in), ear length is 18 mm (0.71 in), and greatest length of skull is 39.4 to 43.9 mm (1.55 to 1.73 in).[Note 3]
In the skull, the rostrum (front part) is large and robust.[7] The nasal bones are short, not extending further back than the lacrimals,[3] and the premaxillaries extend about as far back as the nasals.[37] The zygomatic plate is narrow and lacks a zygomatic notch, an extension of the plate at the front. The plate's back margin is level with the front of the first upper molar. The narrowest part of the interorbital region, located between the eyes, is to the front and its margins exhibit strong beading. Various crests develop on the long braincase, especially in old animals.[7] The parietal bones form part of the roof of the braincase and, unlike in some other rice rats, also extend to the sides of the braincase.[38]
The incisive foramina, perforations of the palate between the incisors and the molars, are short, not extending between the molars.[39] The condition of the posterolateral palatal pits is variable, with some individuals having small pits and others having larger pits that may be recessed into a fossa (depression). The palate is moderately long, extending beyond the molars but not beyond the posterior margins of the maxillary bone. In most specimens, the roof of the mesopterygoid fossa, the gap behind the back of the palate, is not perforated by sphenopalatine vacuities and thus it is fully ossified; if present, these vacuities are small. Mindomys lacks an alisphenoid strut; in some other oryzomyines, this extension of the alisphenoid bone separates two openings (foramina) in the skull, the masticatory–buccinator foramen and the foramen ovale accessorium. There are no openings in the mastoid bone.[3] The squamosal bone lacks a suspensory process that contacts the tegmen tympani, the roof of the tympanic cavity, a defining character of oryzomyines.[40]
In the mandible, the mental foramen, an opening in the mandible just before the first molar, opens to the outside, not upwards as in a few other oryzomyines.[41] The upper and lower masseteric ridges, which anchor some of the chewing muscles, join at a point below the first molar and do not extend forward beyond that point.[3] There is no capsular process of the lower incisor, a trait Mindomys shares with only a few other oryzomyines.[42]
The molars are bunodont (with the cusps higher than the connecting crests) and brachydont (low-crowned).[43] On the upper first and second molar, the outer and inner valleys between the cusps and crests interpenetrate. Many accessory crests are present, including the mesolophs and mesolophids. The anterocone and anteroconid, the front cusps on the upper and lower first molar, are not divided into smaller outer and inner cusps.[3] Unlike in Nectomys, Oryzomys, and Megalomys, the first upper and lower molars usually lack accessory roots,[44] so that each of the three upper molars has two roots on the outer side and one on the inner side and each of the lower molars has one root at the front and one at the back.[3]
A rare species, Mindomys hammondi is known only from Ecuador.[45] Between 1913 and 1980, eight specimens were collected at Mindo,[46] a "tiny agricultural community"[15] at 1,264 m (4,147 ft) elevation in Pichincha Province, northwestern Ecuador. Another specimen is labeled as having been collected on July 27, 1929, by the Olalla family of professional collectors in Concepción, a locality in the Amazon basin lowlands of Napo Province, around 300 to 500 m (980 to 1,640 ft) above sea level. If this record is correct, Mindomys would be unique among small, non-flying mammals native to Ecuador in occurring at relatively low elevations on both sides of the Andes.[46] Furthermore, other collectors working in the same area in Napo have failed to find Mindomys, and the date the specimen was reportedly collected does not accord with the dates reported for the visit of the Olallas to Concepción, rendering its provenance dubious.[47] There are two other locations named "Concepción" in northwestern Ecuador, and Diego Tirira suggested in 2007 that the specimen may instead be from one of these. Another specimen is known from Chaco, Imbabura Province, at an altitude of 630 m (2,070 ft).[29]
Citing unpublished work by Tirira and Percequillo, the 2009 IUCN Red List reports that Mindomys is known from eleven specimens collected at four localities in northwestern Ecuador, and that its altitudinal range extends from 1,200 to 2,700 m (3,900 to 8,900 ft) above sea level, but does not give details.[2] The species occurs in moist, montane forest on the foothills of the western Andes.[48]
Almost nothing is known of the biology of Mindomys.[29] In 1999, Eisenberg and Redford suggested that the species may live in trees;[49] in 2007, Tirira agreed, citing the animal's broad feet. Tirira also suggested that it is nocturnal (active during the night) and solitary and eats fruits, seeds, and insects.[29] According to the 2009 IUCN Red List, it lives on the ground and "apparently has some affinity with water".[2]
The IUCN Red List lists Mindomys hammondi as "endangered" in view of its small known distribution and a continuing decline in the extent and quality of its habitat. Up to 40% of its habitat may already have been destroyed, and the species was last recorded in 1980. It is not known to occur in any protected areas,[2] but has been recorded close to the protected forest of Mindo-Nambillo. It prefers well-conserved primary forest.[29]
Mindomys hammondi, also known as Hammond's rice rat or Hammond's oryzomys, is an endangered 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 then genus Mindomys, but its relationships remain obscure; some evidence supports a placement near Oecomys or as a basal member of Oryzomyini.
Mindomys hammondi is known only from Ecuador, where it occurs in montane forest; a record from the Amazon basin lowlands is dubious. Reportedly, it lives on the ground and is associated with water; others suggest it lives in trees. A large, long-tailed, and long-whiskered rat, its fur is buff above and abruptly lighter below. The front part of the skull (rostrum) is heavily built.
The species is named after the collector who first found it, Gilbert Hammond. He supplied natural history specimens to Oldfield Thomas and others.
Oryzomys hammondi Oryzomys generoko animalia da. Karraskarien barruko Sigmodontinae azpifamilia eta Cricetidae familian sailkatuta dago.
Oryzomys hammondi Oryzomys generoko animalia da. Karraskarien barruko Sigmodontinae azpifamilia eta Cricetidae familian sailkatuta dago.
Mindomys hammondi (Thomas, 1913) è un roditore della famiglia dei Cricetidi, unica specie del genere Mindomys (Weksler, Percequillo & Voss, 2006), endemico dell'Ecuador.[1][2]
Roditore di grandi dimensioni, con la lunghezza della testa e del corpo tra 173 e 203 mm, la lunghezza della coda tra 222 e 251 mm, la lunghezza del piede tra 40 e 42 mm, la lunghezza delle orecchie tra 18 e 19 mm.[3]
Il cranio presenta un rostro lungo e robusto, la regione inter-orbitale ha i bordi convergenti, la scatola cranica è allungata e provvista di una cresta sagittale ben sviluppata. I fori palatali sono corti.
Sono caratterizzati dalla seguente formula dentaria:
3 0 0 1 1 0 0 3 3 0 0 1 1 0 0 3 Totale: 16 1.Incisivi; 2.Canini; 3.Premolari; 4.Molari;La pelliccia è folta. Le parti dorsali sono bruno-giallastre, mentre le parti inferiori sono biancastre o giallastre con la base dei peli grigia. Le vibrisse sopraciliari sono molto lunghe. Le orecchie sono piccole e variano dal marrone scuro al nerastro. I piedi sono larghi, la pianta è provvista di sei cuscinetti carnosi ben sviluppati e il quinto dito è allungato. La coda è più lunga della testa e del corpo ed è uniformemente scura. Le femmine hanno quattro paia di mammelle.
È una specie terricola, associata ad ambienti acquatici. Probabilmente si arrampica agilmente sugli alberi.
Questa specie è limitata al versante andino nord-occidentale dell'Ecuador nella provincia di Pichincha.
Vive nelle foreste subtropicali montane tra 1.200 e 2.700 metri di altitudine.
La IUCN Red List, considerato l'estensione del proprio areale inferiore a 5.000 km², la popolazione circoscritta a soltanto cinque località e il continuo declino nell'estensione e nella qualità del proprio habitat, classifica M.hammondi come specie in pericolo (EN).[1]
Mindomys hammondi (Thomas, 1913) è un roditore della famiglia dei Cricetidi, unica specie del genere Mindomys (Weksler, Percequillo & Voss, 2006), endemico dell'Ecuador.
Mindomys hammondi is een knaagdier uit de Oryzomyini dat voorkomt in Ecuador. De soort is bekend van een aantal exemplaren uit Mindo (waar het geslacht naar genoemd is) en één exemplaar uit het oosten van Ecuador (een deel van het Amazonebekken). Het is de enige soort van het geslacht Mindomys. Deze soort wordt meestal tot Oryzomys gerekend, maar recent onderzoek suggereert dat M. hammondi niet nauw verwant is aan Oryzomys zelf, maar in plaats daarvan een verwant is van Oecomys of de zustergroep is van de gehele Oryzomyini.
De rugvacht is geelbruin, de buikvacht geel of wit, met een scherpe scheiding. De oren zijn kort. Bij het begin van de klauwen aan de achtervoet zitten wat haren. De zeer lange staart is donker van kleur.
Mindomys hammondi is een knaagdier uit de Oryzomyini dat voorkomt in Ecuador. De soort is bekend van een aantal exemplaren uit Mindo (waar het geslacht naar genoemd is) en één exemplaar uit het oosten van Ecuador (een deel van het Amazonebekken). Het is de enige soort van het geslacht Mindomys. Deze soort wordt meestal tot Oryzomys gerekend, maar recent onderzoek suggereert dat M. hammondi niet nauw verwant is aan Oryzomys zelf, maar in plaats daarvan een verwant is van Oecomys of de zustergroep is van de gehele Oryzomyini.
De rugvacht is geelbruin, de buikvacht geel of wit, met een scherpe scheiding. De oren zijn kort. Bij het begin van de klauwen aan de achtervoet zitten wat haren. De zeer lange staart is donker van kleur.
Mindomys hammondi é uma espécie de roedor da família Cricetidae. É a única espécie descrita para o gênero Mindomys.
É endêmica do Equador.
Mindomys hammondi é uma espécie de roedor da família Cricetidae. É a única espécie descrita para o gênero Mindomys.
É endêmica do Equador.
Mindomys hammondi[3] är en däggdjursart som först beskrevs av Thomas 1913. Mindomys hammondi är ensam i släktet Mindomys som ingår i familjen hamsterartade gnagare.[4][5] Inga underarter finns listade i Catalogue of Life.[4]
Arten listades fram till 2006 i släktet risråttor.[2]
Denna gnagare är bara känd från bergstrakter i Ecuador. Den lever i regioner som ligger 1200 till 2700 meter över havet. Arten vistas i tropiska bergsskogar och i molnskogar. Den går främst på marken och dessutom kann den simma.[1]
Wikimedia Commons har media som rör Mindomys hammondi.
Mindomys hammondi är en däggdjursart som först beskrevs av Thomas 1913. Mindomys hammondi är ensam i släktet Mindomys som ingår i familjen hamsterartade gnagare. Inga underarter finns listade i Catalogue of Life.
Arten listades fram till 2006 i släktet risråttor.
Denna gnagare är bara känd från bergstrakter i Ecuador. Den lever i regioner som ligger 1200 till 2700 meter över havet. Arten vistas i tropiska bergsskogar och i molnskogar. Den går främst på marken och dessutom kann den simma.
Mindomys hammondi là một loài động vật có vú trong họ Cricetidae, bộ Gặm nhấm. Loài này được Thomas mô tả năm 1913.[3]
Bài viết liên quan đến phân họ gặm nhấm Sigmodontinae này vẫn còn sơ khai. Bạn có thể giúp Wikipedia bằng cách mở rộng nội dung để bài được hoàn chỉnh hơn. Mindomys hammondi là một loài động vật có vú trong họ Cricetidae, bộ Gặm nhấm. Loài này được Thomas mô tả năm 1913.
해먼드쌀쥐(Mindomys hammondi)는 비단털쥐과 쌀쥐족에 속하는 설치류의 일종이다.[2][3] 이전에 남아메리카물쥐속과 쌀물쥐속, 메갈로미스속, 쌀쥐속의 근연종으로 간주했으며, 현재는 별도의 해먼드쌀쥐속(Mindomys)에 속하는 유일종으로 취급한다.
다음은 2006년 웩슬러 등(Weksler_et_al..)[4]의 연구에 기초한 계통 분류이다.
쌀쥐족우카얄리물쥐속, 맥코넬쌀쥐속, 핸들리쥐속, 큰머리쌀쥐속, 해먼드쌀쥐속, 톰스쌀쥐속,
나무쌀쥐속, 안데스횡단쌀쥐속
해안쌀쥐속, 세하두쌀쥐속, 흰반점산악쥐속, 회색쌀쥐속, 습지쥐속, 큰습지쥐속, 검은쌀쥐속,
남아메리카물쥐속, 갈라파고스쌀쥐속, 쌀쥐속, 브라질가짜쌀쥐속, 쌀물쥐속, 파라과이쌀쥐속
