Range extension of Lundomys molitor ( Winge , 1887 ) ( Mammalia : Rodentia : Cricetidae ) to eastern Rio Grande do Sul state , Brazil

The distribution range of Lundomys molitor, a cricetid rodent species known from only six localities, herein is extended about 295 km with the inclusion of a record from Rio Grande do Sul state. The new locality represents the easternmost limit of the distribution of this poorly studied species.

The description of Hesperomys molitor Winge (1887) was based on a fossil collected by Peter W. Lund from caves near Lagoa Santa, Minas Gerais, Brazil.Many years later, Voss & Carleton (1993) synonymized this fossil with Holochilus magnus, a large and rare cricetid described for Uruguay and southern Brazil (Hershkovitz 1955), and based on derived morphological characters placed it into the Oryzomyini tribe with the status of a new genus.Thus, Lundomys molitor remains as the single representative of a monotypic genus from the Oryzomyini radiation (Voss & Carleton 1993;Weksler 2003Weksler , 2006)).
Lundomys molitor is characterized by a semiaquatic habit, hence being restricted to proximities to freshwater, such as marshes and streams bordered by grass and brush (Marques 1988;Voss & Carleton 1993).Moreover, regardless of its larger distribution in past times during Pleistocene and early Holocene (see Voss & Carleton 1993;Pardinãs & Teta 2011), L. molitor presents a current range distribution restricted to only five localities in Uruguay and a single locality in Brazil.Here, we provide an unreported old record of L. molitor in Brazil and extend its geographical distribution.
We examined five specimens (Table 1) classified as Holochilus brasiliensis and one as Holochilus magnus housed at the mammal collections of the Museu de Zoologia da Universidade de São Paulo, São Paulo (MZUSP).
The craniodental measurements were based on Voss et al. (2000) and taken with digital calipers to the nearest 0.01 mm: condyle-incisive length (CIL); length of the diastema (LD); crown length of the upper molar series (LM), breadth of first upper molar (BM1); length of the incisive foramina (LIF); breadth of the incisive foramina (BIF); breadth of the palatal bridge (BPB); breadth of the zygomatic plate (BZP); length of the rostrum (LR); length of nasals (LN); interorbital breadth (LIB); breadth across the squamosal zygomatic processes (ZB); breadth of the braincase (BB); zygomatic length (ZL).The craniodental values are shown in Table 1.
The main characteristics of L. molitor are a very large body size with unicolored dark long tail, which is much longer than the combined head-and-body length (Table 1); large whitish hindfeet, with well-developed interdigital webs that extends beyond the first phalanges among digits II, III, and IV; feet with five small plantar pads and fringes of silvery hair along plantar margins, without ungular tufts; the dorsal pelage of the body is soft, long and dense, with a yellowish-brown coloration (darker dorsally and lighter at sides); ventral pelage is paler than lateral and dorsal, with gray-based and buffy tipped hairs; small ears with short, brownish or yellowish fur, without contrast with the remaining dorsal pelage (Figure 1) (Voss & Carleton 1993;Voss 2015).
Based on these characters, we advocate that five Holochilus brasiliensis specimens from MZUSP from São Lourenço do Sul (31°22ʹ12ʺ S, 051°58ʹ48ʺ W) were misclassified, and with basis on its resemblance with an individual (MZUSP 10081) of Holochilus magnus (= L. molitor) from Bañado de Tropa Vieja, Uruguay, are also representatives of Lundomys molitor.Cranial dimensions (Table 1) matches the interval described for the species (Table 1: Voss & Carleton 1993).Unfortunately, no external and sex data are available for the São Lourenço do Sul specimens.
Notably few particular characters from São Lourenço do Sul specimens are a little different from those described in literature and the specimen from Canelones (MZUSP 10081).These features refer to the incisive foramina length, which although is notably long and extends very near to the level of the first molar alveoli (M1), it never reaches or surpasses M1 (Figure 3F); and to the poorly developed mesoloph/ids on upper and lower first (M1/m1) and second molars (M2/m2) (Figure 4).Conversely the specimen from Canelones and those described by Voss andCarleton (1993) andFreitas (1988) present the incisive foramina length distinctively extending between or posteriorly to M1, and more developed mesoloph/ids on M1/M2 and m1/m2.
The unreported record from São Lourenço do Sul extends the distribution area of the species about 295 km from its  The important role of specimens deposited in biological collections has been long debated through many different aspects of its importance (e.g., Patterson 2002;Vivo et al. 2014;Brandão 2015;Ceríaco et al. 2016).Our results reinforce the important role of scientific collections with continued maintenance, as the record presented here is from 1904, more than 100 years old.The lack of registered occurrence of L. molitor in recent years might be related to the capture methods used or to local extinction caused by anthropogenic impact.
Nevertheless, this species is still not considered under extinction risk locally or globally (see Marques et al. 2002;Gonzalez et al. 2008).There is a paucity of information on the distribution and population conditions of L. molitor, thus this species is considered Data Deficient on the Rio Grande do Sul threatened species list (Decreto 51797).We hypothesize that its conservation status may change in the near future with the inclusion of L. molitor in lists of threatened species, at least locally, since the increasing land use modifications in southern Brazilian grasslands (Pampas biome) makes it one of the most impacted biomes in Brazil (Overbeck et al. 2007).

Figure 4 .
Figure 4. Upper right (A) and lower left (B) molar toothrows in occlusal view.