Abstract: Molecular biology evidence from mitochondrial 12S RNA and cytochrome b genes indicate that Eospalax baileyi and Eospalax cansus are descended from a common ancestor. However,they both spend their whole lives underground and have similar life-styles,resulting in homoplasy in their skulls and teeth. This homoplasy thus has resulted in classification controversies and confusion of application. In order to make clear distinctions between these two zokor species,we examined morphological differences between internal organs of Eospalax baileyi and those in Eospalax cansus.E. baileyi inhabit the eastern and middle region of Qinghai Province,the southern region of Gansu,and the western region of Xizang. E. cansus inhabits the loess plateau regions such as Shaanxi Province,Gansu Province,Ningxia and the eastern part of Qinghai Province. The habitat climate of E. baileyi is colder than that of E. cansus,and at higher altitude. Oxygen partial pressure is lower as well. So according to the geographical distribution and the potential selection pressures,we conducted a comparative study measuring the 21 internal organs indices between the two zokor species. The field work was carried out in the
eastern Qinghai Province in spring,2011. Captured animals were dissected on the spot. The species of each specimen was identified,and age and sex were also determined. Measurements of weight were taken before dissecting. The internal organs were carefully removed and the digestive tracts were separated from adhesive and adipose tissue. Weights of stomach,small intestine,large intestine,caecum (all without contents),heart,liver,spleen,kidney,and lung,and lengths of small intestine, large intestine and caecum were measured. Our results showed that:the wet and dry masses and the length indices of small intestine from E. baileyi were conspicuously greater than that of E. cansus, -1. 3,1.25 and 1. 69 times respectively .The wet and dry masses of stomach,wet masses of kidney and large intestine from E. cansus were conspicuously greater than that of E. baileyi. There were no significant differences between the two zokor species in the wet and dry weights of liver and spleen,the wet weights of lung,the dry masses of kidney, caecum and large intestine and the length of large intestine.These results present one way to distinguish the two zokor species using the length of small intestine.The way we recommend in this article is easier,more economical and reliable compared with previous classification methods.So it is more suitable for the application in zokor surveys.

关键词: 甘肃鼢鼠, 高原鼢鼠, 内脏器官, 形态差异, 分类