Ulises Francisco J. Pardiñas

Enlarging rodent diversity in west-central Argentina: a new species of the genus Holochilus (Cricetidae, Sigmodontinae)

Abstract On the basis of an adult individual collected in 1955 plus 3 mandibles of latest Holocene age, we describe a new living species of the amphibious rat Holochilus (Sigmodontinae, Oryzomyini) from west-central Mendoza Province, Argentina. The new species is characterized by its short tail, broad zygomatic plate with rounded anterior–superior corner, bony palate without excrescences, large mesolophostyle in the upper first molars and complex upper third molar shorter than the second, and lacking the hypoflexus. The morphological traits displayed by this new Holochilus combine features observed in both the H. brasiliensis and H. sciureus groups with others unique among the genus (e.g., absence of hypoflexus). This new species is the southernmost expression of the genus along the western side of its current range, where it appears isolated in the middle part of the Río Atuel. The finding reported here uncovers and highlights unexpected diversity in southern South American arid lands. Resumen En base a un individuo adulto obtenido en 1955 y tres mandíbulas del Holoceno más tardúo se describe una nueva especie viviente de la rata anfibia Holochilus (Sigmodontinae, Oryzomyini) del centro-oeste de la provincia de Mendoza, Argentina. La nueva especie se caracteriza por su cola corta, placa zigomática ancha con el extremo anterodorsal redondeado, paladar óseo sin excrecencias, primeros molares superiores con mesolofostilos bien desarrollados y tercer molar superior complejo sin hipoflexo y más corto que el segundo molar superior. Los rasgos morfológicos que muestra esta nueva especie de Holochilus combinan características observadas en los grupos de especies de H. brasiliensis y H. sciureus como así también otras únicas en el contexto del género (e.g., ausencia de hipoflexo). Esta nueva especie es la expresión más austral del género en la porción occidental de su rango de distribución y parece estar aislada en el cauce medio del río Atuel. El hallazgo reportado aquí destaca una diversidad insospechada en las tierras áridas del sur de América del Sur.

A new species of the tetraploid vizcacha rat Tympanoctomys (Caviomorpha, Octodontidae) from central Patagonia, Argentina

Abstract A new living species of the desert-adapted tetraploid rodent Tympanoctomys (Caviomorpha, Octodontidae) is described. The new form is restricted to the type locality in Chubut Province, central Patagonia, Argentina, although is known from at least 4 additional Holocene-aged localities along the middle and lower valley of the Chubut River. Tympanoctomys sp. nov. is smaller than the living T. barrerae, its general coloration is yellowish (reddish in T. barrerae) and its tail is equal to ∼43–50% of head and body length (∼49–53% in T. barrerae). Its skull and dentition are characterized by a unique combination of morphological traits, including narrow and posteriorly acuminate nasals (broad and barrel-shaped in T. barrerae), supraoccipital not laterally expanded (expanded in T. barrerae), and 8-shaped lower 3rd molar (comma-shaped in T. barrerae and †T. cordubensis). Morphometric and genetic evidence supports the specific distinction of this Patagonian endemic Tympanoctomys, also characterized by smaller sperm than T. barrerae. The reduced range of the new species, coupled with its recent extinction from the Chubut River valley and the potential impact of large uranium mining projects in central Patagonia, suggest that this species faces a severe extinction risk in the short term. Resumen Se describe una nueva especie viviente del roedor tetraploide desertícola Tympanoctomys (Caviomorpha, Octodontidae). La nueva forma está restringida a su localidad tipo en la provincia del Chubut, Patagonia central, Argentina, si bien es conocida al menos de 4 localidades de edad Holoceno a lo largo del valle medio e inferior del río Chubut. Tympanoctomys sp. nov. es más pequeña que la viviente T. barrerae; su coloración general es amarillenta (rojiza en T. barrerae) y su cola es relativamente más corta (∼43–50% de la longitud cabeza–cuerpo versus ∼49–53% en T. barrerae); su cráneo y dentición están caracterizados por una combinación única de rasgos morfológicos, incluyendo nasales estrechos y posteriormente acuminados (anchos y con forma de barril en T. barrerae), supraoccipital no expandido lateralmente (expandido en T. barrerae) y tercer molar inferior en forma de 8 (en forma de coma en T. barrerae y †T. cordubensis). Diferencias morfométricas y genéticas robustecen la distinción específica de este Tympanoctomys patagónico endémico, también caracterizado por espermatozoides más pequeños que los de T. barrerae. Su reducido rango de distribución, en conjunción con su extinción reciente en el curso medio e inferior del río Chubut y el potencial impacto de extensivos proyectos mineros en Patagonia central sugieren que esta especie enfrenta un riesgo severo de extinción en el corto plazo.

Description of a new soft-haired mouse, genus Abrothrix (Sigmodontinae), from the temperate Valdivian rainforest

Analyses of morphological and molecular data indicate the existence of an unrecognized and unnamed species of soft-haired mouse, genus Abrothrix. Here, we name and describe this new species, which inhabits the Valdivian ecoregion, from the north of Chiloé Island onto the mainland in the Chilean regions of Los Lagos and Los Ríos; it also occurs at a single locality in the Argentinean province of Neuquén. Long confused with A. sanborni, the new species presents a unique combination of characters that differentiate it in external, cranial, phallic, and dental terms from its congeners. Phylogenetic analysis, based on cytochrome-b gene sequences, indicates that the new species is sister to a clade formed by the austral species A. lanosa and A. sanborni and differs on average from them by 5.7% and 5.2%, respectively. Results based on the nuclear Fgb-I7 locus are less conclusive regarding the phylogenetic position of the new species but also show its distinction. We comment on the conservation significance of our findings, considering that forests of the Valdivian ecoregion are suffering substantial human disturbance through intensive logging.

New data on Abrawayaomys chebezi (Rodentia, Cricetidae), a poorly known South American sylvan rodent

Abstract Abrawayaomys chebezi is a spiny sigmodontine believed endemic to the Atlantic Forest of Misiones Province, Argentina. The available knowledge is largely restricted to the holotype, the only fully vouchered specimen. Here, we detail a second specimen, a subadult male obtained in the Parque Provincial Urugua-í (Misiones). The morphology of this animal confirms several diagnostic traits of A. chebezi, such as its smaller size relative to Abrawayaomys ruschii, the type species of the genus, and the simplified occlusal structure of its molars. New data on soft anatomy indicate that chebezi has a unilocular-hemiglandular stomach, no gall bladder, and a complex tridigitate penis with an external surface covered by rounded spines. A rich parasite assemblage including fleas and mites was recorded from this animal. A preliminary review of the alpha taxonomy of Abrawayaomys suggests the possible existence of three different species in the genus, one still unnamed.

First record of the bushy-tailed jird, Sekeetamys calurus (Thomas, 1892) (Rodentia: Muridae) in Oman

Abstract In order to improve the knowledge of terrestrial fauna in the Jabal Samhan Reserve – in southern Oman – several systematic surveys have been carried out in this region. Four specimens of the bushy-tailed jird, the gerbilline Sekeetamys calurus (Thos.) were collected from three localities. This is the first record for the species in Oman and also the first evidence that this jird is in a protected area along its known distribution range. This new record also enlarges the elevational limit known for the species, from 600 m to 1484 m. The animals obtained indicate that S. calurus has reproductive activity in July.

Range extension of Tympanoctomys barrerae (Lawrence, 1941) (Rodentia: Octodontidae) in Patagonia and southernmost record

We report the southernmost record for the octodontid rodent T. barrerae , which is also the second recording locality for this species in Patagonia. The new locality is placed in S Neuquen province, extending the known range of the species about 150 km SW from the nearest previous record. Although T. barrerae is considered a highly specialized rodent of salar flats in Monte desert, the record reported here came from an arbustive rocky environment belonging to the Monte- Patagonia ecotone.