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

Muhammad Ameen; Abdul Majid Khan; Rana Manzoor Ahmad; Ayesha Iqbal; Muhammad Akhtar

doi:10.4072/rbp.2021.4.06

Authors

Muhammad Ameen Department of Zoology, University of the Punjab, Lahore, 54000, Pakistan.
Abdul Majid Khan Department of Zoology, University of the Punjab, Lahore, 54000, Pakistan.
Rana Manzoor Ahmad Department of Zoology, University of Okara, Punjab, 56300, Pakistan.
Ayesha Iqbal Department of Zoology, University of the Punjab, Lahore, 54000, Pakistan.
Muhammad Akhtar Department of Zoology, University of the Punjab, Lahore, 54000, Pakistan.

DOI:

https://doi.org/10.4072/rbp.2021.4.06

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 pentapotamiae and 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.

RESUMO – As flutuações paleoecológicas deixaram suas marcas impressas sobre o esmalte dentário durante o desenvolvimento dos dentes dos mamíferos. Essas marcas podem ser usadas como indicadoras de estresse porque refletem o tipo de pressão enfrentado pelas espécies extintas de mamíferos durante suas vidas. A hipoplasia de esmalte (HE) é um marcador de estresse comum para sugerir o paleoambiente e a probabilidade de extinção de espécies. Para análise de HE, o presente estudo avaliou material pertencente ao gênero Deinotherium, família Deinotheriidae, proveniente do Mioceno Médio (15,2–11,2 Ma) de Siwalik, Paquistão. Nesta análise foram incluídas 35 amostras, consistindo em 52 dentes de duas espécies, Deinotherium pentapotamiae e D. indicum. Os resultados indicam que em 13/52 (25%) dos dentes analisados ocorre EH, indicando que estes deinoterídeos de Siwalik estavam enfrentando um estresse fisiológico e/ou ecológico durante o Mioceno Médio no Paquistão. A elevada frequência de HE em molares (30,30%) em relação aos pré-molares (21,05%) expressa que os indivíduos
experimentaram um estresse comparativamente elevado na fase adulta de suas vidas. A magnitude maior de HE aqui observada em molares
suporta a ideia de estressores ecológicos, ou seja, dieta, acasalamento, doenças e associação presa-predador, aumentando a probabilidade de
extinção por causa das ocorrências de HE.

Palavras-chave: hipoplasia de esmalte, Siwaliks, Mioceno Médio, Proboscidea, Deinotherium, junção raiz coroa.

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