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''Lundomys molitor'', also known as Lund's amphibious rat〔Musser and Carleton, 2005, p. 1124〕 or the greater marsh rat,〔González et al., 2008; Duff and Lawson, 2004, p. 56〕 is a semiaquatic rat species from southeastern South America. Its distribution is now restricted to Uruguay and nearby Rio Grande do Sul, Brazil, but it previously ranged northward into Minas Gerais, Brazil, and southward into eastern Argentina. The Argentine form may have been distinct from the living form from Brazil and Uruguay. ''L. molitor'' is a large rodent, with the head and body length averaging 193 mm (7.60 in), characterized by a long tail, large hindfeet, and long and dense fur. It builds nests above the water, supported by reeds, and it is not currently threatened. Its external morphology is similar to that of ''Holochilus brasiliensis'' and over the course of its complex taxonomic history, it has been confused with that species, but other features support its placement in a distinct genus, ''Lundomys''. Within the family Cricetidae and subfamily Sigmodontinae, it is a member of a group of specialized oryzomyine rodents that also includes ''Holochilus'', ''Noronhomys'', ''Carletonomys'', and ''Pseudoryzomys''. ==Taxonomy== ''Lundomys molitor'' was first described in 1887 by Danish zoologist Herluf Winge, who reviewed the materials Peter Wilhelm Lund had collected in the caves of Lagoa Santa, Minas Gerais, Brazil. Winge used four specimens for his description, including two skull fragments and an isolated maxilla (upper jaw) from the cave chamber Lapa da Escrivania Nr. 5 and a mandible (lower jaw) from Lapa da Serra das Abelhas, but the latter later turned out to be from a different species,〔Voss and Carleton, 1993, p. 6〕 probably ''Gyldenstolpia fronto''.〔Pardiñas et al., 2008, pp. 556–557〕 Lund named the animal ''Hesperomys molitor'' and placed it in the same genus (''Hesperomys'') as what is now ''Pseudoryzomys simplex'' and two species of ''Calomys''. Subsequently, it was rarely mentioned in the literature on South American rodents; those authors who did mention it placed it in either ''Oryzomys'' or ''Calomys''.〔Voss and Carleton, 1993, p. 3〕 In 1926, American zoologist Colin Campbell Sanborn collected some rodents in Uruguay, which he identified as ''Holochilus vulpinus'' (currently ''Holochilus brasiliensis'') in his 1929 report on the collection. When his successor at the Field Museum of Natural History, Philip Hershkovitz, reviewed ''Holochilus'' in 1955, he recognized that the series from Uruguay contained two species, one close to the forms of ''Holochilus'' found across much of South America, and another unique to Uruguay and southern Brazil; he named the latter as a new species, ''Holochilus magnus''. Hershkovitz identified ''Holochilus'' as one of the members of a "sigmodont" group of American rodents, also including ''Sigmodon'', ''Reithrodon'', and ''Neotomys'', on the basis of its flat-crowned molars, which are lophodont (the crown consists of transverse ridges).〔 In 1981, ''H. magnus'' was also recognized in the Late Pleistocene of Buenos Aires Province, Argentina,〔Voss and Carleton, 1993, p. 10〕 and in 1982 it was recorded from Rio Grande do Sul in southern Brazil.〔Oliveira et al. in Freitas et al., 1983〕 In a 1980 article, Argentine zoologist Elio Massoia recognized the resemblance between Winge's ''Hesperomys molitor'' and Hershkovitz's ''Holochilus magnus'', and recommended that the former be reclassified as a species of ''Holochilus'', ''Holochilus molitor''.〔Voss and Carleton, 1993, pp. 3, 6〕 When American zoologists Voss and Carleton restudied Winge's material in a 1993 paper, they were unable to find any consistent differences between the two and accordingly considered them to pertain to the same species.〔Voss and Carleton, 1993, p. 4〕 In addition, they reviewed the differences between this species and other ''Holochilus'' and concluded that these were significant enough to place the former in a distinct genus, which they named ''Lundomys'' after Lund, who had collected the original material.〔Voss and Carleton, 1993, p. 5〕 Since then, the species has been known as ''Lundomys molitor''.〔Musser and Carleton, 2005, p. 1124〕 In the same paper in which they described ''Lundomys'', Voss and Carleton also, for the first time, diagnosed the tribe Oryzomyini in a phylogenetically valid way.〔Voss and Carleton, 1993, p. 31〕 Previously, Oryzomyini had been a somewhat loosely defined group defined among others by a long palate and the presence of a crest known as the mesoloph on the upper molars and mesolophid on the lower molars; this crest is absent or reduced in ''Holochilus'' and ''Lundomys''.〔Voss and Carleton, 1993〕 Voss and Carleton recognized five synapomorphies for the group, all of which are shared by ''Lundomys'';〔 the placement in Oryzomyini of ''Lundomys'' and of three other genera—''Holochilus'', ''Pseudoryzomys'', and ''Zygodontomys''—which also lack complete mesoloph(id)s has been universally supported since.〔Musser and Carleton, 2005; Weksler, 2006〕 Voss and Carleton had found some support for a close relationship between ''Holochilus'', ''Lundomys'', and ''Pseudoryzomys'' within Oryzomyini.〔Voss and Carleton, 1993, p. 1〕 In subsequent years, the related species ''Holochilus primigenus'' and ''Noronhomys vespuccii'' were discovered, providing additional evidence for this grouping.〔Steppan, 1996; Carleton and Olson, 1999〕 The allocation of the former, which is similar to ''Lundomys'' in features of the dentition, to ''Holochilus'' is controversial and placement as a second species of ''Lundomys'' has been suggested as an alternative.〔Pardiñas, 2008, p. 1275〕 A comprehensive phylogenetic analysis of oryzomyines by Marcelo Weksler, published in 2006, supported a close relationship among ''Lundomys'', ''Holochilus'', and ''Pseudoryzomys''; the other species of the group were not included. Data from the sequence of the IRBP gene supported a closer relationship between ''Holochilus'' and ''Pseudoryzomys'', with ''Lundomys'' more distantly related, but morphological data placed ''Holochilus'' and ''Lundomys'' closer together, as did the combined analysis of both morphological and IRPB data.〔Weksler, 2006〕 Subsequently, ''Carletonomys cailoi'' was described as an additional relative of ''Holochilus'' and ''Lundomys''.〔Pardiñas, 2008〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Lundomys」の詳細全文を読む スポンサード リンク
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