Ontogenetic development of dentition in the cave bear
In this contribution the ontogenetic development of dentition in the cave bear (Ursus spelaeus Rosenmüller & Heinroth) is described up to the age of about four years, when the animals became adult and the formation of their teeth was completed. The process of tooth growth and the replacement of deciduous teeth by permanent dentition took place in a similar way as with the present-day brown bear (Ursus arctos Linné). The teeth eruption sequence is the same in both species. The specimens of cave bear jawbones that served for this study were collected from the well-known Palaeolithic site Divje babe I (W Slovenia). Individual age estimations of these jawbones were made on the supposition that a certain ontogenetic stage in the development of cave bear dentition corresponds to an approximately equal age of an individual as with the brown bear. The growth of the jaw, however, was essentially faster in cubs of the cave bear. We also presume that the secondary sex dimorphism in cave bears with males having larger jawbones than females was already expressed in the first year of life. With regard to some indices, especially after noting the obvious discordance between the expected and actually observed mortality profile, we should also consider another possibility; that ontogenetic development in the cave bear was significantly slower than in present-day bears. However, this alternative does not seem very probable, because a proper ontogenetic development has its functional importance. A long time lag in the eruption of permanent molars would mean a certain disadvantage to the species.