Oryzomys albiventer
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Oryzomys albiventer

Oryzomys albiventer is a rodent in the genus Oryzomys of family Cricetidae from interior western Mexico, in the states of Jalisco, Guanajuato, and Michoacán. First described in 1901 as a separate species, it was later lumped under O. couesi and the marsh rice rat (O. palustris ) until it was reinstated as a species in 2009. It differs from neighboring Oryzomys populations in size and measurements and is a large, brightly colored species with a long tail and robust skull and molars. Its range has been much impacted by agricultural development, but isolated populations are thought to persist.

Appearance

Oryzomys albiventer is a large and long-tailed Oryzomys. The upperparts are brightly ochraceous, becoming grayer toward the front. The hairs on the underparts are pale gray near the bases and white in the outer half, so that the underparts appear pale grayish according to Carleton and Arroyo-Cabrales (not white as claimed by Merriman). The tail is dark above and light below. The skull and molars are relatively robust. O. albiventer has broad zygomatic arches (cheekbones), long incisive foramina (perforations of the palate between the incisors and the molars), and long nasal bones that extend behind the premaxillary bones. Compared to its lowland relative O. couesi mexicanus, O. albiventer is larger and more brightly colored and has larger molars but narrower incisive foramina.

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In twelve specimens, total length is 245 to 314 mm (9.6 to 12.4 in), averaging 285.4 mm (11.24 in); head and body length is 116 to 142 mm (4.6 to 5.6 in), averaging 130.0 mm (5.12 in); tail length is 129 to 173 mm (5.1 to 6.8 in), averaging 155.4 mm (6.12 in); hindfoot length is 33 to 40 mm (1.3 to 1.6 in), averaging 36.1 mm (1.42 in); and skull length (occipitonasal length) is 30.0 to 34.5 mm (1.18 to 1.36 in), averaging 32.9 mm (1.30 in).

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Distribution

Geography

O. albiventer occurs at about 1,200 to 1,800 m (3,900 to 5,900 ft) elevation in northern Michoacán, southern Guanajuato, and central and eastern Jalisco, mostly in the area around Lake Chapala. Its range has seen massive agricultural development and although populations may survive, the current distribution of the species is certainly highly fragmented. More survey work is needed to assess the distribution and status of O. albiventer.

Oryzomys albiventer habitat map
Oryzomys albiventer habitat map

References

1. Oryzomys albiventer Wikipedia article - https://en.wikipedia.org/wiki/Oryzomys_albiventer

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