Abstract
Age and sexual variations of eight cranial dimensions in the least horseshoe bat, Rhinolophus coynutus, were examined by classifying 225 males and 219 females from four populations into seven age groups. There were two groups of dimensions which had different tendencies in growth. In females the mastoid width ceased growth at an early stage of age and the other dimensions increased until age group III. In males, the mastoid width and the height of brain-case stopped growth at an early stage of age and the other characters increased until age group II. No clear sexual dimorphism was found in any dimension until two months of age, but appeared thereafter in most of the dimensions, i, e., those of males increased more rapidly than did those of females. However, the dimorphism disappeared again at age group III. The width across upper molars grew faster in females than in males ; the zygomatic width did not show sexual dimorphism after age group I. In the analyses of samples pooled of all age groups, most of the male characters had a tendency to be larger than those of female, excepting the width across upper molars, which was significantly greater in females than in males and the zygomatic width, which did not differ between sexes. Accordingly, it was pointed out that attention for these variations should be paid to compare cranial dimensions in the studies of classification and geographic variation of this species.
