First Report of Enamel Hypoplasia in Extinct Tragulids: A Marker Bearing on Habitat Change
First Report of Enamel Hypoplasia in Extinct Tragulids: A Marker Bearing on Habitat Change
Rana Manzoor Ahmad1,2, Abdul Majid Khan2*, Ayesha Iqbal2, Amtur Rafeh2, Muhammad Tahir Waseem2 and Muhammad Ameen2
ABSTRACT
The present paper is the first ever report on occurrence of enamel hypoplasia in extinct tragulids. The dental defect, enamel hypoplasia is caused by suppressed function of enamel forming cells called ameloblasts. It is used as a reliable stress marker in different extinct mammalian taxa to trace out the level of ecological stress faced by these animals during their life histories. We have studied this defect in three extinct Siwalik tragulid species including; Dorcabune anthracotherioides, Dorcatherium majus and Dorcatherium minus. To assess habitat stability for the Neogene tragulids, dental remains from the middle Miocene-early Pliocene, ca. 13.5-4.0 Ma outcrops of the Siwalik of Pakistan were analyzed for the occurrence of linear enamel hypoplasia. According to our results there was a lower occurrence of enamel hypoplasia (13%) in the tragulid fossils from the middle Miocene outcrops (13.5-11.2 Ma) as compared to the late Miocene to the early Pliocene (11.2-4.0 Ma) tragulid remains (48%) which is statistically significant (p<0.05). The middle Miocene in the Siwaliks is hypothesized to have had warm and humid climatic conditions with dominance of dense forests whereas in the late Miocene to the early Pliocene there was a shift in the ecological conditions, with grasslands expanding at the expense of forests and woodlands and the climate gradually becoming less warm and humid. The current enamel hypoplasia results indicate that warm and humid dense forests were the preferred habitats for extinct tragulids present during the middle Miocene in the Siwaliks.
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April 2020
Vol. 52, Iss. 2, Pages 425-824
