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Thomasomys ucucha

Thomasomys ucucha, also known as the Ucucha Thomasomys, is a species of rodent in the genus Thomasomys of family Cricetidae. It is found only in the Cordillera Oriental of eastern Ecuador.

The first three specimens were collected in 1903 at Tablon, Pichincha Province, by L. Soderstrom. It was not found again until 1978 and 1980, when Robert S. Voss of the American Museum of Natural History collected a total of forty-three specimens at Papallacta in Napo Province. In 2003, he formally described the animal as a new species, Thomasomys ucucha, in a publication in American Museum Novitates in which he also reviewed the mammal fauna of Papallacta. The specific name, ucucha, is the local Quechua word for "mouse". It most closely resembles T. hylophilus, which is found further north in Colombia and Venezuela.

It is a medium-sized Thomasomys with a relatively long tail. The dense, fine, and soft fur is dark brown on the upperparts, changing gradually into the grey underparts. Sparse short, dark hairs are present on the ears. The tail is dark and hardly furred, except for a pencil of long hairs at the end; some animals have a white tail tip. In thirty-six specimens, head and body length is , averaging ; tail length is , averaging ; hindfoot length is , averaging ; ear length is , averaging ; and weight is , averaging .

The front (rostral) part of the skull is short, the interorbital region (between the eyes) is narrow, and the braincase is robust. The incisive foramina, which perforate the palate between the incisors and the molars, are short. The palate itself is also short, not extending beyond the third molars. The upper incisors are procumbent and heavily pigmented with orange. The molars are more hypsodont (high-crowned) than in other Thomasomys.

The animals from Papallacta were collected in a variety of habitats at altitude, including paramo (high-mountain grassland with shrubs and forest patches) and subalpine rain forest. Most were taken in animal runways and a few alongside small streams or on a low tree. Other muroid rodents found at the same places include two akodontines (grass mice), Akodon latebricola and Akodon mollis; two ichthyomyines (water rats), Anotomys leander and Neusticomys monticolus; two oryzomyines (rice rats), Microryzomys altissimus and M. minutus; Chilomys instans; and five other species of Thomasomys, T. aureus, T. baeops, T. cinnameus, T. erro, and T. paramorum.

Its conservation status has been assessed as "vulnerable" by the IUCN because of its small distribution; it may be threatened by the destruction of its habitat for agricultural purposes.

Literature cited

Musser, G.G. and Carleton, M.D. 2005. Superfamily Muroidea. Pp. 8941531 in Wilson, D.E. and Reeder, D.M. (eds.). Mammal Species of the World: a taxonomic and geographic reference. 3rd ed. Baltimore: The Johns Hopkins University Press, 2 vols., 2142 pp. ISBN 978-0-8018-8221-0

Pacheco, V., Tirira, D. and Boada, C. 2008. . In IUCN. IUCN Red List of Threatened Species. Version 2009.2. < www.iucnredlist.org>. Downloaded on December 10, 2009.

Voss, R.S. 2003. A new species of Thomasomys from eastern Ecuador, with remarks on mammalian diversity and biogeography in the Cordillera Oriental. American Museum Novitates 3421:147.

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This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article Thomasomys ucucha

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