Ontogenetic and sexual variation in cranial characters of Kerodon rupestris Wied, 1820 (Rodentia, Caviidae)

Resumen

Kerodon rupestris has been considered as a monospecific species within Caviidae, which can be easily diagnosed by the outstanding, forward projected orofacial region of the skull. This species has been found since Pleistocene until the Recent inhabiting exposed granitic islands in the semi-arid region of northeastern Brazil. Qualitative and quantitative cranial characters were investigated along ontogeny of 188 individuals from Campos Sales, in Ceará State, and on 16 specimens found in association to Pleistocene fauna in limestone caves in Bahia State. Patterns of suture fusion, development of cranial processes, and foramina condition allow the determination of five age classes. The age criterion, developed for recent specimens, was applied to estimate relative ages of 16 individuals collected in the caves. Despite differences in geographic and stratigraphic origins, two ages classes of cave’s adults were revealed. Twenty-two distances between cranial anatomical landmarks analyzed using descriptive statistics, analysis of variance (ANOVA), and principal component showed significant discrimination among age classes. As expected, a crescent grown between classes was detected. When compared with the same age classes of recent specimens, the cave’s individuals were largest in 21of 22 characters measured. Sexual variation was investigated by size free discriminant analyses and the results show that males are larger than females. Sexes have a great common area in the morphological space.