Characteristics and differences between skulls of Myospalax psilurus and Myospalax aspalax

Because of the representative nature of the information carried by the mammalian skull for all mammalian life activities, studies of the skull can not only provide a basis for mammalian taxonomy, but also provide fundamental information for exploring how mammalian adaptive evolution has shaped species morphology. Therefore, to identify the morphological differences in the adaptive evolution of neighboring, closely related species with respect to their habitats, this study compared the external morphology of the skull of Myospalax psilurus (specimen 26) with that of M. aspalax (specimen 17) and selected 13 representative items, including the profile length, basal length, median palatal length, zygomatic breadth, and least breadth between the orbits, and used body weight as a covariate for covariance analysis. The results showed that the the length of the down tooth row of the two species of zokors differed significantly between the sexes (P < 0.01), whereas the profile length of the skull, the median palatal length, and greatest length of the nasals differed only between the sexes of M. aspalax (P < 0.05). The length of the tympanic bulla differed only between sexes in M. psilurus (P < 0.05), and there was no significant difference between the sexes in M. aspalax. Interspecific variation analysis revealed 10 morphometric indices of total cranial length, basal length, and median palatal length (P < 0.05). In addition, nine skull indicators, including the total cranial length of the skull of M. psilurus, were significantly positively correlated with weight gain (P < 0.05), whereas only the orbital width showed a very significant negative correlation (P < 0.01). Only five M. aspalax data indicators, including total cranial length, base length, and zygomatic width, were significantly positively correlated with weight gain (P < 0.05). Differences in skull morphological indicators between M. psilurus and M. aspalax were observed in several categories. The cranial length, basal length, zygomatic width, dentition length, and upper dentition row length remained in the same state of growth into adulthood for both zokor species, with growth sites being more abundant in M. psilurus than in M. aspalax, and its interorbital width became narrower with an increasing body weight.