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<document>
<title>Lundomys</title>
<authors>Wikipedia</authors>
<publisher>wikipedia.org</publisher>
<publishedplace>network</publishedplace>
<publishedyear>2010</publishedyear>
<edition></edition>
<category>Mammals of Brazil</category>
<section id="39877" fatherid="0" title="" lv="" priority="-1" level="1">
Lundomys molitor, also known as Lund's Amphibious RatMusser 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 east into Minas Gerais, Brazil, and west into eastern Argentina. The Argentinean 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.

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<section id="39878" fatherid="0" title="Taxonomy" lv="" priority="-2" level="1">
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 upper jaw from the cave chamber Lapa da Escrivania Nr. 5 and a 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 Lund named the animal Hesperomys molitor and placed it in the same genus 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, Argentinean 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

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<section id="39879" fatherid="0" title="Description" lv="" priority="-3" level="1">
Lundomys molitor is among the largest living oryzomyines, rivaled only by some large forms of Holochilus and Nectomys, but it is substantially smaller than some of the recently extinct Antillean species, such as "Ekbletomys hypenemus" and Megalomys desmarestii.Weksler, 2006, table 8; Voss and Myers, 1991, table 1; Ray, 1962, tables 7, 11 Unlike in Holochilus brasiliensis, which occurs in the same area, the tail is longer than the head and body.Voss and Carleton, 1993, p. 13 It is sparsely haired and dark, and there is no difference in color between the upper and lower side. The coat, which is long, dense, and soft, is yellow–brown at the sides, but becomes darker on the upperparts and lighter on the underparts.Voss and Carleton, 1993, p. 7 The large hindfeet are characterized by conspicuous interdigital webbing, but they lack tufts of hair on the digits and several of the pads are reduced.Voss and Carleton, 1993, p. 6; Weksler, 2006, p. 23 As in some other semiaquatic oryzomyines, fringes of hair are present along the plantar margins and between some of the digits.Voss and Carleton, 1993, p. 7; Weksler, 2006, pp. 24–25 The forefeet also lack tufts on the digits and show very long claws, a character unique among oryzomyines.Weksler, 2006, pp. 19, 23 The female has four pairs of teats and the gall bladder is absent, both important characters of oryzomyines.Voss and Carleton, 1993; Weksler, 2006, table 5 The head and body length is 160 to 230 mm (6.30 to 9.06 in), averaging 193 mm (7.60 in), the tail length is 195 to 255 mm (7.68 to 10.04 mm), averaging 235 mm (9.25 in), and the length of the hindfoot is 58 to 68 mm (2.28 to 2.68 in), averaging 62 mm (2.44 in).Measurements for head and body length and tail length are from 10 specimens and those for hindfoot length are from 12 specimens, all from Uruguay.Voss and Carleton, 1993, table 2.
The front part of the skull is notably broad. As in Holochilus, the zygomatic plate, the flattened front portion of the cheek bone, is expansive and produced into a spinous process at the anterior margin. The jugal bone is small, but less reduced than in Holochilus.Voss and Carleton, 1993, p. 15 The interorbital region of the skull is narrow and flanked by high beads. The incisive foramina, which perforate the palate between the incisors and the upper molars, are long, extending between the molars. The palate itself is also long, extending beyond the posterior margin of the maxillary bones,Voss and Carleton, 1993, p. 16; Weksler, 2006, pp. 34–35 and it is perforated near the third molars by conspicuous posterolateral palatal pits.Voss and Carleton, 1993, p. 16 As in all oryzomyines, the squamosal bone lacks a suspensory process that contacts the tegmen tympani, the roof of the tympanic cavity, but Lundomys is unusual in that the squamosal and the tegmen tympani usually overlap when viewed from the side.Weksler, 2006, p. 40; Voss and Carleton, 1993, p. 17 In the mandible, the angular and coronoid processes are less well-developed than in Holochilus.Voss and Carleton, 1993, p. 17 The capsular process of the lower incisor, a slight raising of the mandibular bone at the back end of the incisor, near the coronoid process, is small. The two masseteric ridges, to which some of the chewing muscles are attached, are entirely separate, joining only at their anterior edges, which are located below the first molar.Weksler, 2006, p. 47
The molars are slightly more high-crowned (hypsodont) than in most oryzomyines and many of the accessory crests are reduced, but they are sharply distinct from the highly derived, hypsodont molars of Holochilus.Voss and Carleton, 1993, p. 19 The main cusps are located opposite each other and have rounded edges. The enamel folds do not extend past the midlines of the molars. The mesoloph, an accessory crest on the upper molars that is usually well-developed in oryzomyines, is present but short on the first and second upper molar; it is much more reduced in Holochilus and Pseudoryzomys.Voss and Carleton, 1993, p. 20; Weksler, 2006, fig. 25 The corresponding structure on the lower molars, the mesolophid, is present on the first and second molars in Lundomys, but absent in both Holochilus and Pseudoryzomys.Voss and Carleton, 1993, p. 20; Weksler, 2006, p. 49 Another accessory crest, the anteroloph, is present, though small, on the first upper molar in Lundomys, but entirely absent in both other genera.Weksler, 2006, p. 45 As in Holochilus and Pseudoryzomys, the anterior cusp on the first lower molar, the anteroconid, contains a deep pit.Voss and Carleton, 1993, p. 20 Each of the three upper molars has three roots; unlike in both Holochilus and Pseudoryzomys, the first upper molar lacks an accessory fourth root.Weksler, 2006, pp. 42–43 The first lower molar has four roots, including two small accessory roots located between larger anterior and posterior roots. The second molar has either two or three roots, with the anterior root split into two smaller roots in some specimens.Weksler, 2006, p. 43
The karyotype contains 52 chromosomes with a total of 58 major arms (2n = 52, FN = 58). The non-sex chromosomes (autosomes) are mostly acrocentric, having a long and a short arm, or telocentric, having only one arm, but there are also three large metacentric pairs, which have two major arms, and a small metacentric pair. The Y chromosome is metacentric and the X chromosome is variable, ranging from nearly metacentric to acrocentric in five specimens studied.Freitas et al., 1983; Voss and Carleton, 1993, p. 10

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<section id="39880" fatherid="0" title="Distribution and ecology" lv="" priority="4" level="1">
Lundomys molitor has been found as a living animal only in Uruguay and nearby Rio Grande do Sul; records of live specimens from eastern Argentina and Lagoa Santa, Minas Gerais, have not been confirmed. It is rarely encountered and it has been collected in only one location in Rio Grande do Sul, but this may be due to insufficient efforts to locate it, rather than genuine rarity.González et al., 2008; Bonvicino et al., 2008 Its distribution is generally limited to areas with mean winter temperatures over 12 °C (54 °F), mean annual temperatures over 18 °C (64 °F), annual rainfall over 1,100 mm (43 in), and a long rainy season averaging over 200 days. It is usually found in swamps or near streams.Teta and Pardiñas, 2006, p. 179
Pleistocene fossils have been found throughout its current range and beyond it. In Uruguay and Rio Grande do Sul, the Lujanian (Late Pleistocene to Early Holocene) Sopas Formation has yielded remains of L. molitor, in addition to such other mammals as the extinct saber-toothed cat Smilodon populator and species of Glyptodon, Macrauchenia, and Toxodon.Oliveira and Kerber, 2009; Ubilla et al., 2004 The type locality, Lagoa Santa, lies far northeast of the nearest record of live L. molitor; there, it is known only from three skull fragments from a cave known as Laga da Escrivania Nr. 5. This cave also contains numerous remains of members of the extinct South American megafauna, such as ground sloths, litopternans, gomphotheres, and glyptodonts, in addition to 16 species of cricetid rodents, but it is not certain that all remains from this cave are from the same age.Voss and Myers, 1991, table 5, p. 429
Remains of Lundomys have been found at six Pleistocene localities in Buenos Aires Province, Argentina, which suggests a warm and humid paleoclimate there.Teta and Pardiñas, 2006 The oldest deposits, at Bajo San José, date to Marine Isotopic Stage 11, about 420,000 to 360,000 years ago, younger specimens from other localities are as little as 30,000 years old.Teta and Pardiñas, 2006, p. 180 The younger Argentinean Lundomys specimens are subtly distinct from living Lundomys in some features of the first lower molar and may represent a distinct species. One lower first molar of this form has length 3.28 mm.Pardiñas and Lezcano, 1995, pp. 258–259 Because the Bajo San José material does not contain lower first molars, it is impossible to determine whether this material also pertains to the later Argentinean Lundomys form. The morphology of the upper and lower jaw precludes an identification as Holochilus primigenus, a fossil species with molar traits almost identical to those of Lundomys.Pardiñas and Deschamps, 1995, p. 850 The length of the upper toothrow of one specimen from this locality is 8.50 mm (0.3346 in) and the length of the upper first molar is 3.48 mm (0.1370 in),Pardiñas and Deschamps, 1995, table 2 slightly smaller than in living Lundomys, which ranges from  3.56 to 3.64 mm (0.1402 to 0.1433 in) in four specimensPardiñas, 2008, table 1

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<section id="39881" fatherid="0" title="Natural history" lv="" priority="-5" level="1">
Lundomys molitor is semiaquatic in habits, spending much of its time in the water, and is active during the night.Voss and Carleton, 1993, p. 34 An excellent swimmer,Carleton and Olson, 1999, p. 52 it is even more specialized for swimming than is Holochilus.Hershkovitz, 1955, p. 658 It builds a spherical nest among reeds in up to 1.5 m (5 ft) deep water, usually about 20 cm (8 in) above the water. The material for the nest, which is 25 to 30 cm (10 to 12 in) in diameter and 9 to 11 cm (about 4 in) in height, comes from the surrounding reeds. Its wall consists of three layers, surrounding a central chamber, which is connected to the water by a ramp, also composed of reeds.Sierra de Soriano in Voss and Carleton, 1993, p. 34 Nests built by members of the related genus Holochilus are similar in many details. Several dissected stomachs contained green plant material, suggesting that it is herbivorous, like Holochilus.Barley in Voss and Carleton, 1993, p. 34 A female caught in April was pregnant with three embryos, which were about 12 mm (0.47 in) long.Tuttle in Voss and Carleton, 1993, p. 32 The mite Gigantolaelaps wolffsohni has been found on specimens of L. molitor in Uruguay.Lareschi et al., 2006 Other rodents found in association with it include Scapteromys tumidus, Oligoryzomys nigripes, Reithrodon auritus, Akodon azarae, Oxymycterus nasutus, and Holochilus brasiliensis.Voss and Carleton, 1993, pp. 32–34
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<section id="39882" fatherid="0" title="Conservation status" lv="" priority="6" level="1">
The species' conservation status is currently assessed as "least concern" by the International Union for Conservation of Nature, reflecting a relatively wide distribution and the absence of evidence for a decline in populations. Several of the areas where it occurs are protected, but the destruction of its habitat may pose a threat to its continued existence.
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<section id="39883" fatherid="0" title="Footnotes" lv="" priority="-7" level="1">
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<section id="39884" fatherid="0" title="References" lv="" priority="-8" level="1">
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<section id="39885" fatherid="0" title="Literature cited" lv="" priority="-9" level="1">
Category:Mammals of Brazil
Category:Mammals of Uruguay
Category:Oryzomyini

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