Appraisal of dental enamel hypoplasia in the Middle Miocene Deinotheriidae: implications of the Siwalik paleoenvironment of Pakistan

Abstract

The paleoecological fluctuations left their impression marks on the tooth enamel of mammals during their tooth development. These marks can be used as stress indicators because they reflect the type of duress faced by the extinct mammalian species during their lives. The enamel hypoplasia (EH) is a common stress marker to trace out the paleoenvironment of the region and the likelihood of species extinction. The material used for current EH analysis belongs to the genus Deinotherium, family Deinotheriidae, collected from Middle Miocene (15.2–11.2 Ma) Siwaliks of Pakistan. In this analysis 35 samples consisting of 52 teeth of two species, Deinotherium pentapotamiaeand D. indicum are included. The results indicate that 13/52 (25%) of the analyzed teeth have occurrences of EH giving a prediction that these Siwalik deinotheriids were facing the physiological and/or ecological stresses during the Middle Miocene epoch of Pakistan. The higher frequency of EH in molars (30.30%) compared to premolars (21.05%) express that the individuals experienced a comparatively high stress at the adult stages of their lives. This higher magnitude of EH in molars supports the idea of ecological stressors, i.e., dietary, mating, disease, and predator-prey associations, amplify the likelihood of extinction by dint of EH occurrences. Keywords: enamel hypoplasia, Siwaliks, Middle Miocene, Proboscidea, Deinotherium, root crown junction