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INTRODUCTION: Rhipidomys is the second most specious and the most widespread genus of the tribe Thomasomyini. Chromosomal data have been an important tool in the taxonomy of the group that presents low variability of diploid number (2n) and highly variable fundamental numbers (FNs). Despite such diversity, the genus has been studied mainly by classical and banding cytogenetic techniques. METHODS: This study performed a comparative study between R. emiliae (2n = 44, FN = 52), R. macrurus (2n = 44, FN = 49), R. nitela (2n = 50, FN = 71), and R. mastacalis (2n = 44, FN = 72) using chromosome painting probes of two Oryzomyini species. RESULTS: Our analysis revealed pericentric inversion as the main rearrangement involved in the karyotype evolution of the group, although tandem fusions/fissions were also detected. In addition, we detected eight syntenic associations exclusive of the genus Rhipidomys, and three syntenic associations shared between species of the tribe Thomasomyini and Oryzomyini. CONCLUSION: Comparative cytogenetic analysis by ZOO-FISH on genus Rhipidomys supports a pattern of chromosomal rearrangement already suggested by comparative G-banding. However, the results suggest that karyotype variability in the genus could also involve the occurrence of an evolutionary new centromere.

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The Lesser Antillean island chain in the eastern Caribbean formerly supported a diverse rodent fauna including multiple endemic genera of oryzomyine rice rats. The Caribbean rice rats are now all extinct, with most island populations known only from Holocene palaeontological and zooarchaeological material and with many remaining taxonomically undescribed. Rice rat material is reported from several pre-Columbian Ceramic Age (late Holocene) archaeological sites on the Grenada Bank, including sites on Grenada and Carriacou, but the taxonomic identity and diversity of the Grenada Bank rice rats has remained uncertain. We provide a morphology-based description of rice rats from Grenada and Carriacou, and analyze their phylogenetic and biogeographical affinities to other Caribbean and mainland Neotropical oryzomyines. We recognize two taxa from the Grenada Bank: we describe the new species Megalomys camerhogne from Pearls (Grenada), representing the largest-bodied member of the extinct endemic Caribbean genus Megalomys, and we refer smaller-bodied oryzomyine material from Pearls and Sabazan (Carriacou) to the widespread extant Neotropical species Zygodontomys brevicauda. Body size variation within Megalomys correlates with island bank area and might thus reflect historical rather than modern biogeography. Zygodontomys specimens from the Grenada Bank fall within the upper end of size variation in extant populations and may constitute an example of 'island gigantism', but it is possible that occurrence of this widespread species on the Grenada Bank might reflect prehistoric human-mediated translocation. We predict further endemic Caribbean rice rat taxa remain to be discovered, including a possible species of Megalomys on the neighbouring island of St. Vincent.

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The tribe Oryzomyini is an impressive group of rodents, comprising 30 extant genera and an estimated 147 species. Recent remarkable advances in the understanding of the diversity, taxonomy and systematics of the tribe have mostly derived from analyses of single or few genetic markers. However, the evolutionary history and biogeography of Oryzomyini, its origin and diversification across the Neotropics, remain unrevealed. Here we use a multi-locus dataset (over 400 loci) obtained through anchored phylogenomics to provide a genome-wide phylogenetic hypothesis for Oryzomyini and to investigate the tempo and mode of its evolution. Species tree and supermatrix analyses produced topologies with strong support for most branches, with all genera confirmed as monophyletic, a result that previous studies failed to obtain. Our analyses also corroborated the monophyly and phylogenetic relationship of three main clades of Oryzomyini (B, C and D). The origin of the tribe is estimated to be in the Miocene (8.93-5.38 million years ago). The cladogenetic events leading to the four main clades occurred during the late Miocene and early Pliocene and most speciation events in the Pleistocene. Geographic range estimates suggested an east of Andes origin for the ancestor of oryzomyines, most likely in the Boreal Brazilian region, which includes the north bank of Rio Amazonas and the Guiana Shield. Oryzomyini rodents are an autochthonous South America radiation, that colonized areas and dominions of this continent mainly by dispersal events. The evolutionary history of the tribe is deeply associated with the Andean cordillera and the landscape history of Amazon basin.

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Taxa with broad geographic ranges that occur in different biomes and exhibit plastic morphological traits and/or adaptations to particular habitats make inferences about species boundaries especially challenging. However, technological and conceptual advances in the generation and analysis of genomic data have advanced the description of biodiversity. Here we address the outstanding questions about the delimitation of species in the genus Holochilus, a rodent with morphological specializations to wetland habitats distributed throughoutthe South America, using genome-wide SNP and morphometric data. Specifically, we apply a Bayesian model-based species delimitation that revealed significant re-arrangements of species boundaries based on consideration of both morphometric and genomic data alone, or in combination. With these shifts in species boundaries, our results provide an insightful framework for inferring the group's biogeographic history and considering possible connections between disjoint biomes in South America. Because of the ecological constraints of the marsh rats, and with the proposed taxonomic re-arrangements, the significance of our findings extends beyond systematics and suggests how diversification might be associated with past ecological/environmental changes during the Pleistocene. Overall, this study highlights how genomic data can provide phylogenetic information for resolving relationships among species of Holochilus, but also the importance of integrative approaches to identify evolutionary independent species. For the relatively understudied vast wetlands of South America, a robust species delimitation framework therefore becomes a critical source of data relevant to hypotheses about the history of the biomes themselves.

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Comparative chromosome-painting analysis among highly rearranged karyotypes of Sigmodontinae rodents (Rodentia, Cricetidae) detects conserved syntenic blocks, which are proposed as chromosomal signatures and can be used as phylogenetic markers. In the Akodontini tribe, the molecular topology (Cytb and/or IRBP) shows five low-supported clades (divisions: "Akodon", "Bibimys", "Blarinomys", "Oxymycterus", and "Scapteromys") within two high-supported major clades (clade A: "Akodon", "Bibimys", and "Oxymycterus"; clade B: "Blarinomys" and "Scapteromys"). Here, we examine the chromosomal signatures of the Akodontini tribe by using Hylaeamys megacephalus (HME) probes to study the karyotypes of Oxymycterus amazonicus (2n = 54, FN = 64) and Blarinomys breviceps (2n = 28, FN = 50), and compare these data with those from other taxa investigated using the same set of probes. We strategically employ the chromosomal signatures to elucidate phylogenetic relationships among the Akodontini. When we follow the evolution of chromosomal signature states, we find that the cytogenetic data corroborate the current molecular relationships in clade A nodes. We discuss the distinct events that caused karyotypic variability in the Oxymycterus and Blarinomys genera. In addition, we propose that Blarinomys may constitute a species complex, and that the taxonomy should be revised to better delimit the geographical boundaries and their taxonomic status.

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The nominal species Calomys tener (Winge, 1887) ranges broadly in open lands of the Caatinga, Cerrado, Pantanal and Mata Atlântica of Brazil, and was recently reported from the Pampas of southern Brazil, and in the Selva Paranaense of eastern Paraguay and northeastern Argentina. This rodent can be infected with the pathogenic Araraquara hantavirus in Brazil. Given that most epidemiological studies have not taken into account updated taxonomic findings of their rodent hosts, in this study, we obtained sequence data of the Cyt-b and COI genes of specimens of C. tener from 22 different geographical localities from throughout the currently known distribution of the species (including individuals from Argentina, Paraguay, Bolivia, and Brazil) to test if it constitutes a single genetic unit or if it presents genetic discontinuities that may represent different evolutionary lineages. Phylogenetic analyses including several species of Calomys recovered several clades with strong support. Regarding C. tener, it is recovered as sister to the node that cluster C. laucha (Fischer, 1814) sensu lato, C. expulsus (Lund, 1841) and species in the C. callosus (Rengger, 1830) species complex. At the intraspecific level there are no genetic gaps among haplotypes of C. tener that could suggest more than one species. The recent captures in the Pampas of southern Brazil and in the Selva Paranaense suggest that the species may be colonizing new geographic areas.(AU)

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The nominal species Calomys tener (Winge, 1887) ranges broadly in open lands of the Caatinga, Cerrado, Pantanal and Mata Atlântica of Brazil, and was recently reported from the Pampas of southern Brazil, and in the Selva Paranaense of eastern Paraguay and northeastern Argentina. This rodent can be infected with the pathogenic Araraquara hantavirus in Brazil. Given that most epidemiological studies have not taken into account updated taxonomic findings of their rodent hosts, in this study, we obtained sequence data of the Cyt-b and COI genes of specimens of C. tener from 22 different geographical localities from throughout the currently known distribution of the species (including individuals from Argentina, Paraguay, Bolivia, and Brazil) to test if it constitutes a single genetic unit or if it presents genetic discontinuities that may represent different evolutionary lineages. Phylogenetic analyses including several species of Calomys recovered several clades with strong support. Regarding C. tener, it is recovered as sister to the node that cluster C. laucha (Fischer, 1814) sensu lato, C. expulsus (Lund, 1841) and species in the C. callosus (Rengger, 1830) species complex. At the intraspecific level there are no genetic gaps among haplotypes of C. tener that could suggest more than one species. The recent captures in the Pampas of southern Brazil and in the Selva Paranaense suggest that the species may be colonizing new geographic areas.

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We present herein the record of the monotypic sigmodontine Calassomys apicalis Pardiñas, Lessa, Salazar-Bravo and Câmara 2014 in the Brazilian Cerrado, based on two adult male specimens collected in a rocky outcrops area (campo rupestre) in southern portion of Espinhaço Mountain Range, in May and June 2016. This taxon was previously known only from the type locality at Parque Nacional das Sempre Vivas, Minas Gerais state, Brazil. The fecal analysis of the specimens collected in this study indicates a diversified diet with the consumption of arthropods and vegetative parts of plants in different proportions, being this the first record about the feeding habits of this species.

Um novo registro de Calassomys apicalis (Rodentia, Cricetidae) na Cadeia do Espinhaço, Brasil. Apresentamos aqui o registro do monotípico sigmodontideo Calassomys apicalis Pardiñas, Lessa, Salazar-Bravo e Câmara 2014 no Cerrado Brasileiro, com base em dois espécimes de machos adultos coletados em área de afloramentos rochosos (campo rupestre) na porção sul da Cadeia do Espinhaço, em maio e junho de 2016. Este táxon era anteriormente conhecido apenas da localidade tipo no Parque Nacional das Sempre Vivas, Minas Gerais,Brasil. A análise fecal dos espécimes coletados neste estudo indica uma dieta diversificada com o consumo de artrópodes e partes vegetativas de plantas em diferentes proporções, sendo este o primeiro registro sobre os hábitos alimentares desta espécie.

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We present herein the record of the monotypic sigmodontine Calassomys apicalis Pardiñas, Lessa, Salazar-Bravo and Câmara 2014 in the Brazilian Cerrado, based on two adult male specimens collected in a rocky outcrops area (campo rupestre) in southern portion of Espinhaço Mountain Range, in May and June 2016. This taxon was previously known only from the type locality at Parque Nacional das Sempre Vivas, Minas Gerais state, Brazil. The fecal analysis of the specimens collected in this study indicates a diversified diet with the consumption of arthropods and vegetative parts of plants in different proportions, being this the first record about the feeding habits of this species.(AU)

Um novo registro de Calassomys apicalis (Rodentia, Cricetidae) na Cadeia do Espinhaço, Brasil. Apresentamos aqui o registro do monotípico sigmodontideo Calassomys apicalis Pardiñas, Lessa, Salazar-Bravo e Câmara 2014 no Cerrado Brasileiro, com base em dois espécimes de machos adultos coletados em área de afloramentos rochosos (campo rupestre) na porção sul da Cadeia do Espinhaço, em maio e junho de 2016. Este táxon era anteriormente conhecido apenas da localidade tipo no Parque Nacional das Sempre Vivas, Minas Gerais,Brasil. A análise fecal dos espécimes coletados neste estudo indica uma dieta diversificada com o consumo de artrópodes e partes vegetativas de plantas em diferentes proporções, sendo este o primeiro registro sobre os hábitos alimentares desta espécie.(AU)

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The taxonomic identification of micromammals might be complicated when the study material is fragmented, as it is the case with pellets and fossil material. On the other hand, tooth morphology generally provides accurate information for species identification. Teeth preserve notably well, retaining their original morphology, unlike skulls and mandibles, which can get crushed or have missing parts. Here, we explored a geometric morphometrics approach (GM) to identify fragmented specimens of two sympatric Calomys Waterhouse, 1837 species - Calomys tener (Winge, 1888) and Calomys expulsus (Lund, 1841) - using the morphology of intact molars as the basis for identification. Furthermore, we included some specimens of uncertain taxonomic identification to test their affinities and the utility of the shape of the molar to identify incomplete specimens. We evaluated the variations in the shape of the first upper molar (M1) among 46 owl pellets specimens of Calomys, including C. expulsus (n = 15), C. tener (n = 15), and unidentified specimens treated as Calomys sp. (n = 16) through GM analysis using 17 landmarks. The data was explored using PCA, PERMANOVA, and Discriminant analyses over the Procrustes residuals matrix were applied to evaluate inter- and intraspecific shape differences. Also, we evaluated whether allometric shape differences could impact the data, but found no evidence of a correlation between size and shape. Our results support that shape differences in the M1 are effective for discriminating between C. tener and C. expulsus. Moreover, the unidentified specimens do not represent a third shape but could be identified with confidence either as C. teneror C. expulsus. Our results show that even with fragmentary materials, GM is a feasible and useful tool for exploring inter-specific shape differences and assisting in taxonomic identification as a complement to traditional qualitative description of diagnostic features in poorly preserved specimens.(AU)

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In the present study, Litomosoides silvai parasitizing Akodon montensis in the southern region of Brazil is reported for the first time. New morphological information is provided for some structures of this nematode species, such as a flattened cephalic extremity, presence of two dorsal cephalic papillae, female tail with a constriction at its tip, s shaped vagina, spicules characteristic of the carinii species group and microfilaria tail constricted at the tip. This nematode was found parasitizing the thoracic cavity with a prevalence of 10% (2/20), mean intensity of 4 (6/2), mean abundance of 0.4 (8/20) and range of infection of 2-6 specimens per host, in southern Brazil. This occurrence of L. silvai in A. montensis is a new geographical record for southern Brazil, in the Upper Paraná Atlantic Forest ecoregion of the northwestern region of Rio Grande do Sul, which is part of the Atlantic Forest biome.(AU)

No presente estudo é relatado pela primeira vez Litomosoides silvai parasitando Akodon montensis coletados na região Sul do Brasil. Foram fornecidas novas informações morfológicas para algumas estruturas desta espécie de nematódeo, tais como extremidade cefálica achatada, a presença de duas papilas cefálicas dorsais, cauda das fêmeas com uma constrição na ponta da cauda, vagina em forma de s, espículas de característica do grupo de espécies de carinii e cauda da microfilária com constrição na ponta. Este nematódeo parasitava a cavidade torácica com uma prevalência de 10% (2/20), intensidade média de 4 (8/2) e abundância média de 0,4 (8/20), e intervalo de infecção de 2-6 espécimes por hospedeiro no Sul do Brasil. A ocorrência de L. silvai em A. montensis é um novo registro geográfico, no sul do Brasil, a noroeste do estado do Rio Grande do Sul, na ecorregião da Mata Atlântica do Alto Paraná, parte do bioma da Mata Atlântica.(AU)

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The taxonomic identification of micromammals might be complicated when the study material is fragmented, as it is the case with pellets and fossil material. On the other hand, tooth morphology generally provides accurate information for species identification. Teeth preserve notably well, retaining their original morphology, unlike skulls and mandibles, which can get crushed or have missing parts. Here, we explored a geometric morphometrics approach (GM) to identify fragmented specimens of two sympatric Calomys Waterhouse, 1837 species - Calomys tener (Winge, 1888) and Calomys expulsus (Lund, 1841) - using the morphology of intact molars as the basis for identification. Furthermore, we included some specimens of uncertain taxonomic identification to test their affinities and the utility of the shape of the molar to identify incomplete specimens. We evaluated the variations in the shape of the first upper molar (M1) among 46 owl pellets specimens of Calomys, including C. expulsus (n = 15), C. tener (n = 15), and unidentified specimens treated as Calomys sp. (n = 16) through GM analysis using 17 landmarks. The data was explored using PCA, PERMANOVA, and Discriminant analyses over the Procrustes residuals matrix were applied to evaluate inter- and intraspecific shape differences. Also, we evaluated whether allometric shape differences could impact the data, but found no evidence of a correlation between size and shape. Our results support that shape differences in the M1 are effective for discriminating between C. tener and C. expulsus. Moreover, the unidentified specimens do not represent a third shape but could be identified with confidence either as C. teneror C. expulsus. Our results show that even with fragmentary materials, GM is a feasible and useful tool for exploring inter-specific shape differences and assisting in taxonomic identification as a complement to traditional qualitative description of diagnostic features in poorly preserved specimens.

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The genus Aegialomys was described to encompass the former Oryzomys xanthaeolus group, and includes nowadays two species: A. xanthaeolus and A. galapagoensis. Although not very confusing, the taxonomic history of the genus is long, comprising the description of five nominal taxa along the last 180 years: Mus galapagoensis Waterhouse, 1839; Oryzomys bauri Allen, 1892; Oryzomys xanthaeolus Thomas, 1894; Oryzomys  baroni Allen, 1897; and Oryzomys  xanthaeolus ica Osgood, 1944. Here we gathered and documented all available information about the type material of Aegialomys on which the species names were based, re-described their morphometric and morphological characters, commented their synonyms and taxonomic history, and compiled information about type localities. Additionally, we established a neotype for O. bauri in order to define the nominal taxon objectively.

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The taxonomic status of populations of the genus Phyllotis from northwestern Argentina (NWA) has undergone recent changes, with the addition of two species (P. alisosiensis and P. anitae) to the traditionally recognized forms (P. caprinus, P. xanthopygus, and P. osilae). Three of these species (P. anitae, P. osilae, and P. alisosiensis) were included within the Phyllotis osilae species group. Most authors recognized three subspecies of P. osilae for NWA: P. osilae osilae, P. o. nogalaris, and P. o. tucumanus. Morphological, morphometric, and molecular studies based on recently collected specimens suggest that current classification does not reflect the diversity of this group in NWA, revealing the need of some taxonomic reallocations and new distributional delimitations. Here we propose that P. nogalaris must be recognized as a valid species and the restriction of P. osilae to southern Peru and central Bolivia. Following our results, we expect an outstanding improvement in the taxonomic knowledge of the Phyllotis osilae species group in the coming years.

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The Andean Leaf-eared mouse, Phyllotis andium Thomas 1912, has been considered a widespread medium-size sigmodontine rodent (230 mm of total length and 35 grams approximately) that occurs from Tungurahua, Ecuador, through the Andes, to Lima, Peru. Previous studies performed on Phyllotis noted evidence of morphological geographical variation within the species, which is likely because of the several potential geographical barriers that exist within the distribution range of P. andium. We carried out a taxonomic revision of this species based on qualitative and quantitative morphological analyses of 330 specimens from 92 localities. This included appropriate comparisons with other species of the andium/amicus group and performed molecular analysis based on cytochrome b sequences. As a result, morphologic qualitative analysis suggested the recognition of three different taxa, which are supported by morphologic quantitative and molecular analyses. The three taxa here identified have allopatric distributional ranges separated by important geographic barriers. Following these identification criteria, P. andium is now recognized for the samples from Tungurahua, Ecuador to Huánuco, Peru, and includes melanius and fruticicolus as synonymous; the southern populations from the Ancash and Lima departments, in the western Peruvian Andes, are proposed to represent a new species; and we recognize P. stenops as a valid species with tamborum as a synonym. Finally, we postulate that the diversification of these three species is related to key events in the Andean orogeny.

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Oligoryzomys belongs to the tribe Oryzomyini, and contains about 22 species. Diploid numbers range from 2n = 44 in Oligoryzomys sp. 2 to 2n = 72 in O. utiaritensis and phylogenetic relationships are not well defined. The high morphological convergence leads to misidentification of taxonomic entities and the species are often identified by chromosomal characters. Until now, the genus has been studied only by classical cytogenetic approaches. To understand the chromosomal evolution of Oligoryzomys, we developed chromosome probes from a female of Oligoryzomys moojeni (OMO) with 2n = 70 and hybridized to other five Oligoryzomys species. The probes painted 31 segments on O. fornesi (OFO) with 2n = 62; 32 segments on O. microtis (OMI), 2n = 64; 33 segments on O. nigripes (ONI), 2n = 62 and on O. rupestris (ORU), 2n = 46; and 34 on Oligoryzomys sp. 2 (OSP), 2n = 44. OMO probes 4 and 5 showed a syntenic association in O. fornesi, O. microtis and O. nigripes and were also presented in the same pair, although disrupted, in O. rupestris and Oligoryzomys sp. 2. Concerning O. rupestris and Oligoryzomys sp. 2, species with the lowest diploid numbers of the genus, a total of 8 probes hybridized to 11 segments on the largest pair of ORU 1 and 9 probes hybridized to 12 segments on OSP 1. Also, OMO 6 painted three segments in ORU, corresponding to the proximal segment of ORU 2q, and the whole of ORU 19 and 20. In OSP, the segment corresponding to ORU 20 was homologous to OSP 1p. OMO X showed signals of hybridization in both X and Y chromosomes. Extensive chromosomal rearrangements, that could not be detected by classical cytogenetic techniques, such as pericentric inversions or repositioning of centromeres, Robertsonian rearrangements and tandem fusions/fissions, as well as gain/activation or loss/inactivation of centromeres and telomeric sequences have driven the huge genome reshuffling in these closely related species.

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Currently four species of Holochilus (Cricetidae: Sigmodontinae) are recognized. According to the literature, three species are recorded for Brazil: H. sciureus, H. brasiliensis and H. chacarius. Samples from western Brazil (Mato Grosso and Mato Grosso do Sul states) are usually reported as H. sciureus and, when referring to specimens from the Pantanal, as H. chacarius. However, the taxonomic status of specimens from this region has not been properly evaluated through detailed morphological analyses or voucher specimens. About 110 specimens of Holochilus deposited in Brazilian collections were qualitatively and quantitatively analyzed (univariate and multivariate tests). Our results suggested the existence of three species (H. sciureus, H. brasiliensis and H. chacarius) in Brazil, which present significant morphological and morphometric differences, thus confirming that the Mato Grosso and Mato Grosso do Sul samples, formerly misidentified as H. sciureus, belong to H. chacarius. This species differs from H. sciureus and H. brasiliensis by a series of pelage and skull characters, such as: the coloration of pelage, light orange-brown in the dorsum, light orangish in the flanks and white in the venter; ridges of the masseteric crest confluent at the level (or slightly above) of the mental foramen and at the anterior part of m1, alternated main molar cusps, lophids compressed and with acute outer margins (rarely prismatic), anteromedian fossetid labially displaced and subcircular (small to medium), metaflexid less developed (frequently not reaching the midline of the tooth), proto and hipoconid subrectangular in outline and transversely orientated, mesoflexid transversely orientated and mesoloph absent.(AU)

Quatro espécies de Holochilus (Cricetidae: Sigmodontinae) são atualmente reconhecidas. De acordo com a literatura, três espécies são registradas para o Brasil: H. brasiliensis, H. chacarius e H. sciureus. Amostras provenientes do oeste do Brasil (Estados do Mato Grosso e Mato Grosso do Sul) são geralmente reportadas como H. sciureus e, quando referentes a espécimes do Pantanal, como H. chacarius. Entretanto, o estado taxonômico de espécimes dessa região ainda não foi propriamente avaliado através de análise morfológica detalhada e/ou espécimes testemunho. Cerca de 110 espécimes de Holochilus depositados em coleções brasileiras foram analisados qualitativa e quantitativamente (testes univariados e multivariados). Nossos resultados suportam a existência de três espécies (H. sciureus, H. brasiliensis e H. chacarius) no país, as quais possuem diferenças morfológicas e morfométricas significativas entre si, assim confirmando que as amostras do Mato Grosso e Mato Grosso do Sul, outrora erroneamente identificados como H. sciureus, pertencem à H. chacarius. Esta espécie difere de H. sciureus e H. brasiliensis por apresentar uma série de características da pelagem e do crânio, tais como: coloração da pelagem castanho claro no dorso, levemente alaranjada nas laterais e branca no ventre; crista massetérica confluente ao nível ou ligeiramente acima do forame mental e na parte anterior do m1; principais cúspides molares alternadas; lofideos compactados e com margens externas agudas (raramente prismática), fossetideo anteromediano labialmente deslocado e subcircular (pequeno a médio); metaflexideo menos desenvolvido (muitas vezes não atingindo a linha mediana do dente); protoconideo e hipoconideo subrectangulares e transversalmente orientados; mesoflexideo transversalmente orientado e mesolofo ausente.(AU)

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The Rufous-nosed Mouse Wilfredomys oenax is a rare Sigmodontinae rodent known from scarce records from northern Uruguay and south and southeastern Brazil. This species is underrepresented in scientific collections and is currently classified as threathened, being considered extinct at Curitiba, Paraná, the only confirmed locality of the species at southeastern Brazil. Although specimens from São Paulo were already reported, the presence of this species in this state seems to have passed unnoticed in recent literature. Through detailed morphological analyzes of specimens cited in literature, the present work confirms and discusses the presence of this species in São Paulo state from a specimen collected more than 70 years ago. Recently, by the use of modern sampling methods, other rare Sigmodontinae rodents, such as Abrawayomys ruschii, Phaenomys ferrugineous and Rhagomys rufescens, have been recorded to São Paulo state. However, no specimen of Wilfredomys oenax has been recently reported indicating that this species might be locally extinct. The record mentioned here adds another species to the state of São Paulo mammal diversity and reinforces the urgency of studying Wilfredomys oenax.(AU)

O Rato-do-Mato Wilfredomys oenax é um raro roedor Sigmodontinae conhecido a partir de escassos registros do norte do Uruguai e sul e sudeste do Brasil. Esta espécie é conhecida de poucos espécimes em coleções científicas e está atualmente classificada como ameaçada, sendo considerada extinta em Curitiba, Paraná, o único local confirmado da espécie para o sudeste do Brasil. No entanto, embora espécimes de São Paulo já tenham sido reportados, a presença desta espécie neste estado parece ter passada despercebida na literatura. Através de análise morfológica detalhada de espécimes citados na literatura, o presente trabalho confirma e discute a presença desta espécie para o estado de São Paulo a partir de espécimes coletados há mais de 70 anos atrás. Recentemente, outros raros roedores Sigmodontinae, como Abrawayaomys ruschii, Phaenomys ferrugineous e Rhagomys rufescens, tem sido registrados em localidades de São Paulo através da utilização de métodos modernos de amostragem. Entretanto, nenhum espécime de Wilfredomys oenax foi relatado até o momento, indicando que esta espécie pode estar localmente extinta. Este registro adiciona mais uma espécie para a diversidade de mamíferos do estado de São Paulo e reforça a urgência no estudo de Wilfredomys oenax.(AU)

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RESUMO

Currently four species of Holochilus (Cricetidae: Sigmodontinae) are recognized. According to the literature, three species are recorded for Brazil: H. sciureus, H. brasiliensis and H. chacarius. Samples from western Brazil (Mato Grosso and Mato Grosso do Sul states) are usually reported as H. sciureus and, when referring to specimens from the Pantanal, as H. chacarius. However, the taxonomic status of specimens from this region has not been properly evaluated through detailed morphological analyses or voucher specimens. About 110 specimens of Holochilus deposited in Brazilian collections were qualitatively and quantitatively analyzed (univariate and multivariate tests). Our results suggested the existence of three species (H. sciureus, H. brasiliensis and H. chacarius) in Brazil, which present significant morphological and morphometric differences, thus confirming that the Mato Grosso and Mato Grosso do Sul samples, formerly misidentified as H. sciureus, belong to H. chacarius. This species differs from H. sciureus and H. brasiliensis by a series of pelage and skull characters, such as: the coloration of pelage, light orange-brown in the dorsum, light orangish in the flanks and white in the venter; ridges of the masseteric crest confluent at the level (or slightly above) of the mental foramen and at the anterior part of m1, alternated main molar cusps, lophids compressed and with acute outer margins (rarely prismatic), anteromedian fossetid labially displaced and subcircular (small to medium), metaflexid less developed (frequently not reaching the midline of the tooth), proto and hipoconid subrectangular in outline and transversely orientated, mesoflexid transversely orientated and mesoloph absent.

Quatro espécies de Holochilus (Cricetidae: Sigmodontinae) são atualmente reconhecidas. De acordo com a literatura, três espécies são registradas para o Brasil: H. brasiliensis, H. chacarius e H. sciureus. Amostras provenientes do oeste do Brasil (Estados do Mato Grosso e Mato Grosso do Sul) são geralmente reportadas como H. sciureus e, quando referentes a espécimes do Pantanal, como H. chacarius. Entretanto, o estado taxonômico de espécimes dessa região ainda não foi propriamente avaliado através de análise morfológica detalhada e/ou espécimes testemunho. Cerca de 110 espécimes de Holochilus depositados em coleções brasileiras foram analisados qualitativa e quantitativamente (testes univariados e multivariados). Nossos resultados suportam a existência de três espécies (H. sciureus, H. brasiliensis e H. chacarius) no país, as quais possuem diferenças morfológicas e morfométricas significativas entre si, assim confirmando que as amostras do Mato Grosso e Mato Grosso do Sul, outrora erroneamente identificados como H. sciureus, pertencem à H. chacarius. Esta espécie difere de H. sciureus e H. brasiliensis por apresentar uma série de características da pelagem e do crânio, tais como: coloração da pelagem castanho claro no dorso, levemente alaranjada nas laterais e branca no ventre; crista massetérica confluente ao nível ou ligeiramente acima do forame mental e na parte anterior do m1; principais cúspides molares alternadas; lofideos compactados e com margens externas agudas (raramente prismática), fossetideo anteromediano labialmente deslocado e subcircular (pequeno a médio); metaflexideo menos desenvolvido (muitas vezes não atingindo a linha mediana do dente); protoconideo e hipoconideo subrectangulares e transversalmente orientados; mesoflexideo transversalmente orientado e mesolofo ausente.

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RESUMO

The Rufous-nosed Mouse Wilfredomys oenax is a rare Sigmodontinae rodent known from scarce records from northern Uruguay and south and southeastern Brazil. This species is underrepresented in scientific collections and is currently classified as threathened, being considered extinct at Curitiba, Paraná, the only confirmed locality of the species at southeastern Brazil. Although specimens from São Paulo were already reported, the presence of this species in this state seems to have passed unnoticed in recent literature. Through detailed morphological analyzes of specimens cited in literature, the present work confirms and discusses the presence of this species in São Paulo state from a specimen collected more than 70 years ago. Recently, by the use of modern sampling methods, other rare Sigmodontinae rodents, such as Abrawayomys ruschii, Phaenomys ferrugineous and Rhagomys rufescens, have been recorded to São Paulo state. However, no specimen of Wilfredomys oenax has been recently reported indicating that this species might be locally extinct. The record mentioned here adds another species to the state of São Paulo mammal diversity and reinforces the urgency of studying Wilfredomys oenax.

O Rato-do-Mato Wilfredomys oenax é um raro roedor Sigmodontinae conhecido a partir de escassos registros do norte do Uruguai e sul e sudeste do Brasil. Esta espécie é conhecida de poucos espécimes em coleções científicas e está atualmente classificada como ameaçada, sendo considerada extinta em Curitiba, Paraná, o único local confirmado da espécie para o sudeste do Brasil. No entanto, embora espécimes de São Paulo já tenham sido reportados, a presença desta espécie neste estado parece ter passada despercebida na literatura. Através de análise morfológica detalhada de espécimes citados na literatura, o presente trabalho confirma e discute a presença desta espécie para o estado de São Paulo a partir de espécimes coletados há mais de 70 anos atrás. Recentemente, outros raros roedores Sigmodontinae, como Abrawayaomys ruschii, Phaenomys ferrugineous e Rhagomys rufescens, tem sido registrados em localidades de São Paulo através da utilização de métodos modernos de amostragem. Entretanto, nenhum espécime de Wilfredomys oenax foi relatado até o momento, indicando que esta espécie pode estar localmente extinta. Este registro adiciona mais uma espécie para a diversidade de mamíferos do estado de São Paulo e reforça a urgência no estudo de Wilfredomys oenax.

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