关键词: 沟牙田鼠, 形态, 分类

Abstract: Bedford's vole (Proedromys bedfordi) is a very rare rodent distributed in western Sichuan and southern Gansu province, People's Republic of China. At present, only three specimens have been collected. The taxonomic status of Bedford's vole has elicited controversy. Many zoologists put this species in Microtus. During a baseline survey of the Jiuzhaigou National Nature Reserve in 2003, 16 specimens of Bedford’s vole were collected. The skull, teeth, glans penis were studied. Results show that the third lower and upper molar of adults differ from those of juvenile voles. The upper incisor is very broad (>2.5 mm). The outcrop of the lower incisor is very short (<4.0 mm). The length of the lower incisor is only 77 % of length of the mandible. The third upper molar is very distinct; its tooth loop is sector-like or bean-like. Morphology of the glans penis is very distinct; its proximal baculum is flask-like. The distal base of the baculum is markedly enlarged. The overall outline of the skulls of Bedford's vole is significantly bent. Morphology of the upper jaw teeth of young Bedford's voles is narrow and strip-like. And the lower jaw teeth give the appearance of a contrary "E". All these characteristics of Bedford’s vole differ from species within other genera in the same family. For example, the upper incisors in these comparative species are much narrower (<2.44 mm). In addition, in comparative species the outcrop of lower incisors is longer (>4.5 mm), the length of the lower incisor exceeds 80% percent of the mandible, the outline of the skull is very flat, the base of the proximal baculum is rhombus or round, the distal baculum is stick-like, and the lateral baculum is ossified. The stark contrasts that are apparent in these comparisons clearly indicate that Bedford's vole belongs to a single genus: Proedromys

Key words: Bedford’s vole（Proedromys bedfordi）, Morphology, Taxonomy