Root-Like Formation of Upper Incisors in Captive Rock Hyrax (Procavia capensis)

The upper incisors of rock hyraxes have been considered hypselodonts without intraspecific variation such as age and sex. This study analyzed 32 specimens aged 1–14 years reared at zoos to examine the tooth base and pulp cavity morphologies of the upper incisors. The results revealed that in female upper incisors, both the tapering of the tooth base and the narrowing of the pulp cavity became more pronounced with age. In individuals aged under eight years of age, no significant sex differences were observed in either the tooth base or pulp cavity morphologies. However, in individuals aged eight years and older, a significant sex difference was found in the tooth base morphology. In contrast, no significant sex difference was observed in the pulp cavity morphology in this age group. These results suggest that the upper incisors of rock hyraxes exhibit sexual dimorphism; in females, they are hypsodontic and cease growing as they age, whereas in males, they are hypselodontic and continue to grow throughout their lives. This sexual dimorphism in upper incisors may be attributed to the use of these teeth by male rock hyraxes during intraspecific aggression.