Taxonomia dos camundongos-do-mato, gênero Oligoryzomys Bangs, 1900 (Rodentia, Sigmodontinae) do Cerrado brasileiro, com a descrição de duas novas espécies

We present a taxonomic overview of the species of Oligoryzomys from the Brazilian Cerrado. We recognize seven species, including two described herein, making Oligoryzomys one of the most diverse mammalian genera of the Cerrado morphoclimatic domain. Oligoryzomys chacoensis occurs in the Cerrado and Chaco morphoclimatic domains. Oligoryzomys flavescens is distributed mainly in the Atlantic Forest of Brazil and the Pampas region of Argentina and Uruguay, but is also found in gallery forest in the Cerrado of Brazil near the border of the Atlantic Forest. Oligoryzomys stramineus and O. fornesi occur in the Cerrado and Caatinga morphoclimatic domains. Oligoryzomys nigripes is found in the Atlantic Forest and in the Southern portion of the Cerrado. The two new species are endemic to the Cerrado, and one of them is found only in “campo rupestre” vegetation. Oligoryzomys eliurus and O. delticola are placed tentatively as junior synonyms of O. nigripes. Oligoryzomys fornesi is recognized as a distinct species from O. microtis.Apresentamos uma revisão taxonômica das espécies do gênero Oligoryzomys do Cerrado brasileiro. Reconhecemos sete espécies, incluindo duas aqui descritas, tornando Oligoryzomys um dos mais diversos gêneros de mamíferos do domínio morfoclimático do Cerrado. Oligoryzomys chacoensis ocorre nos domínios morfoclimáticos do Cerrado e do Chaco. Oligoryzomys flavescens se distribui principalmente na Mata Atlântica do Brasil e na região dos pampas da Argentina e Uruguai, mas é também encontrado em matas de galeria no Cerrado do Brasil próximo do limite com a Mata Atlântica. Oligoryzomys stramineus e O. fornesi ocorrem nos domínios morfoclimáticos do Cerrado e da Caatinga. Oligoryzomys nigripes é encontrado na Mata Atlântica e na porção sul do Cerrado. As duas novas espécies são endêmicas do Cerrado, e uma delas é encontrada apenas na vegetação de “campo rupestre”. Oligoryzomys eliurus e O. delticola são tentativamente consideradas sinônimos juniores de O. nigripes. Oligoryzomys fornesi é reconhecida como uma espécie distinta de O. microtis

Phylogenetic relationships of oryzomyine rodents (Muroidea, Sigmodontinae)

Includes bibliographical references (p. 90-99).149 p. : ill., maps ; 26 cm.In this study I provide a phylogenetic hypothesis for the tribe Oryzomyini that can be used to understand the diversification and evolution of this group of rodents and to revise the current generic-level classification. Morphological and molecular data were used for these purposes in combined and separate analyses. Molecular data consisted of partial sequences (1266 bp) from the first exon of the nuclear gene encoding the interphotoreceptor retinoid binding protein (IRBP); the morphological matrix comprised 99 characters, including 16 integumental characters, 32 skull characters, 29 dental characters, 7 postcranial characters, and 10 characters from the phallus and soft-anatomy systems. I present anatomical descriptions for each character, including delineation of different states observed among oryzomyines. Results of the combined analysis were congruent with the IRBP-only dataset for oryzomyine higher-level relationships. Morphological analyses, although showing discrepancies from the combined or IRBP consensus cladograms and with low nodal support values, recovered several clades similar to the combined and IRBP analyses. Systematics of the tribe and the evolution of a few pivotal characters are discussed in light of the proposed phylogeny. Different taxonomic arrangements for species currently included in the genus Oryzomys are suggested. Finally, I evaluate evolutionary and biogeographic hypotheses that are compatible with our current knowledge on oryzomyine relationships

Redescription of the enigmatic long-tailed rat Sigmodontomys aphrastus (Cricetidae: Sigmodontinae) with comments on taxonomy and natural history

Sigmodontomys aphrastus, the long-tailed rat, is an exceedingly rare rodent species from montane regions of Central and South America of which very little is known ecologically or systematically. It has been variously placed in the genera Oryzomys, Nectomys, and Sigmodontomys based on the five previously known specimens. Recent phylogenetic analyses (Weksler 2006) have shown that S. aphrastus occurs in a monophyletic clade composed of S. alfari and Melanomys caliginosus with M. caliginosus as the proposed sister taxon. Two new individuals were collected in northwestern Costa Rica’s Cordillera de Tilarán. These new specimens and the other five known specimens are used to redescribe the species, detail measurements of external and cranial morphology, and compare S. aphrastus to similar appearing, sympatric species (Nephelomys albigularis and N. devius) and proposed closely related species (Sigmodontomys alfari, Mindomys hammondi, and Melanomys caliginosus). New ecological data is presented and the general knowledge of its natural history is summarized. The phylogenetic relatedness of S. aphrastus with purported sister taxa remains unresolved until combined molecular and morphological analyses are conducted.Resumen—Sigmodontomys aphrastus, la rata de cola larga, es una especie rara de rodedor de las montañas de America Central y Sur de la cual se conoce muy poco acerca de su ecología y sistemática. Esta especie ha sido clasificada en el género Oryzomys, Nectomys, y Sigmodontomys basado en solo cinco especímenes. Análisis filogenéticos recientes (Weksler 2006) han demonstrado que S. aphrastus se encuentra en un clado monofilético compuesto de S. alfari y Melanomys caliginosus con M. caliginosus propuesto como la especie hermana. Dos nuevos individuos fueron recolectados en el noreste de Costa Rica en la Cordillera de Tilarán. Estos dos nuevos especímenes y junto con los cinco anteriores son usados a describir nuevamente la especie, detallar sus medidas morfométricas externas y craneales, y comparar S. aphrastus con especies simpátricas similares (Nephelomys albigularis and N. devius) y especies que han sido propuestas como dentro del mismo clado (Sigmodontomys alfari, Mindomys hammondi, y Melanomys caliginosus). Presentamos nuevos datos ecológicos y resumimos el conocimiento de su historia natural. La relación filogenética de S. aphrastus con las especies propuestas como del mismo clado no sera resuelto hasta que analisis moleculares y morfologicos sean llevados a cabo

A newly recognized clade of trans-Andean Oryzomyini (Rodentia: Cricetidae), with description of a new genus.

We expand upon recent studies on relationships within the Oryzomyini, in particular, those involving taxa currently assigned to the genus Sigmodontomys. In recent years, Sigmodontomys has been treated as including 2 species, alfari (J. A. Allen, 1897) and aphrastus (Harris, 1932), but throughout their complicated taxonomic history both species also have been placed in the genus Oryzomys, and alfari independently in Nectomys. Using morphological (98 external, cranial, dental, and postcranial) and molecular (nuclear interphotoreceptor retinoid-binding protein gene and mitochondrial cytochrome-b and ribosomal 12S RNA genes) characters, we infer the phylogenetic position of these 2 species within Oryzomyini. We document that alfari and aphrastus do not form a monophyletic group. Sigmodontomys alfari is most closely related to Melanomys, and aphrastus is either the sister to that clade, or to the extinct Caribbean genus Megalomys. Thus, aphrastus is best regarded as representing a new genus, which is described and named herein. This new genus falls within the Sigmodontomys–Melanomys–Aegialomys–Nesoryzomys clade, which forms a monophyletic group of mainly southern Central American and northern South American taxa primarily restricted to lowland to midelevation montane trans-Andean habitats and possessing a marked ability to cross expanses of salt water. The new genus occurs in middle elevations from north-central Costa Rica to northwestern Ecuador and along with some populations of Aegialomys and Melanomys occupies the highest elevations for members of this group. Resumen—A partir de estudios recientes, profundizamos acerca de las relaciones filogenéticas dentro de Oryzomyini (Rodentia: Cricetidae), en particular aquellas que involucran taxa actualmente atribuidos al género Sigmodontomys. Recientemente se ha considerado que Sigmodontomys incluye dos especies—alfari (J. A. Allen, 1897) y aphrastus (Harris, 1932), sin embargo, a través de su complicada historia taxonómica, ambas especies también han sido incluidas dentro del género Oryzomys, y alfari independientemente dentro del género Nectomys. Usando caracteres morfológicos (98 externos, craneales, dentales y postcraneales) y moleculares (citocromo b, 12S y IRBP), inferimos la posición filogenética de estas dos especies dentro de Oryzomyini. Documentamos que alfari y aphrastus no forman un grupo monofilético. Sigmodontomys alfari es el taxón hermano de Melanomys, mientras aphrastus es hermano de dicho grupo, o del género caribeño extinto Megalomys. Por consiguiente, consideramos a aphrastus como un nuevo género que describimos y nombramos a continuación. Este nuevo género está incluido dentro del clado formado por Sigmodontomys–Melanomys–Aegialomys–Nesoryzomys, el cual representa un grupo monofilético bien sustentado principalmente del sur de Centroamérica y norte de Sudamérica, restringido principalmente a hábitats de tierras bajas a elevaciones intermedias trasandinas, y caracterizado por su habilidad de cruzar barreras de agua salada. El nuevo género se encuentra en elevaciones medianas y altas desde el centro y norte de Costa Rica hasta el noroeste de Ecuador y, junto con algunas poblaciones de Aegialomys y Melanomys, ocupa las elevaciones más altas de cualquier miembro de este grupo

A new genus of oryzomyine rodents (Cricetidae, Sigmodontinae) with three new species from montane cloud forests, western Andean cordillera of Colombia and Ecuador

The Andean cloud forests of western Colombia and Ecuador are home to several endemic mammals; members of the Oryzomyini, the largest Sigmodontinae tribe, are extensively represented in the region. However, our knowledge about this diversity is still incomplete, as evidenced by several new taxa that have been described in recent years. Extensive field work in two protected areas enclosing remnants of Chocó montane forest recovered a high diversity of small mammals. Among them, a medium-sized oryzomyine is here described as a new genus having at least three new species, two of them are named and diagnosed. Although externally similar to members of the genera Nephelomys and Tanyuromys, the new genus has a unique molar pattern within the tribe, being characterized by a noticeable degree of hypsodonty, simplification, lamination, and third molar compression. A phylogeny based on a combination of molecular markers, including nuclear and mitochondrial genes, and morphological data recovered the new genus as sister to Mindomys, and sequentially to Nephelomys. The new genus seems to be another example of a sigmodontine rodent unique to the Chocó biogeographic region. Its type species inhabits cloud forest between 1,600 and 2,300 m in northernmost Ecuador (Carchi Province); a second species is restricted to lower montane forest, 1,200 m, in northern Ecuador (Imbabura Province); a third putative species, here highlighted exclusively by molecular evidence from one immature specimen, is recorded in the montane forest of Reserva Otonga, northern Ecuador (Cotopaxi Province). Finally, the new genus is also recorded in southernmost Colombia (Nariño Department), probably represented there also by a new species. These species are spatially separated by deep river canyons through Andean forests, resulting in marked environmental discontinuities. Unfortunately, Colombian and Ecuadorian Pacific cloud forests are under rapid anthropic transformation. Although the populations of the type species are moderately abundant and occur in protected areas, the other two persist in threatened forest fragments.Fil: Brito, Jorge. Instituto Nacional de Biodiversidad; EcuadorFil: Koch, Claudia. Zoologisches Forschungsmuseum Alexander Koenig.; AlemaniaFil: Reis Percequillo, Alexandre. Universidade do Sao Paulo. Escola Superior de Agricultura Luiz de Queiroz; BrasilFil: Tinoco, Nicolás. Pontificia Universidad Católica del Ecuador; EcuadorFil: Weksler, Marcelo. Universidade Federal do Rio de Janeiro; BrasilFil: Pinto, C. Miguel. Observatorio de Biodiversidad Ambiente y Salud; EcuadorFil: Pardiñas, Ulises Francisco J.. Instituto Nacional de Biodiversidad; Ecuador. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto de Diversidad y Evolución Austral; Argentin

First record of Drymoreomys albimaculatus Percequillo, Weksler & Costa, 2011 (Rodentia, Cricetidae, Sigmodontinae) in Rio de Janeiro state, Brazil

Here we report the first record of Drymoreo­mys albimaculatus Percequillo, Weksler & Costa, 2011 (Cricetidae, Sigmodontinae) in Rio de Janeiro state, Brazil. One specimen was captured at Serra da Bocaina National Park, municipality of Paraty. The specimen was captured in a pitfall trap, in a mixed habitat of forest and bamboo. The karyotype showed 2n = 62 and FN = 62, which is similar to the previously described for the species