The skull differences between two sexes based on 22 skull morphological indexes. A, E. cansus; B, M. aspalax; C, E. rothschildi; D, E. baileyi. The samples in black and white represent males and females, respectively. * represents highly significant difference (p < 0.05); ** represents significant difference (p < 0.01) and ns represents no significant difference (p > 0.05).