Diet and habitat changes among Siwalik herbivorous mammals in response to Neogene and Quaternary climate changes: An appraisal in the light of new data

Abstract

Late Miocene climate change particularly monsoon intensification brought about by tectonic upheavals changed significantly the regional vegetation scenario of the Indian Subcontinent. Siwalik Middle Miocene closed forests gave way to Late Miocene open and seasonal forests, which in turn were gradually replaced by latest Miocene and Early Pliocene wooded grasslands. Here, new stable isotope and microwear data of a Late Miocene rhizomyid rodent, and dental microwear analyses of selected Late Miocene, and Plio-Pleistocene large and small herbivorous mammals from India is presented. These findings are then integrated with the earlier palaeodiet and palaeohabitat data of Siwalik mammals, in order to get an overall picture of climate vis a vis dietary and habitat change between ∼14 and ∼1 Ma. The results indicate that the Late Miocene rhizomyid Rhizomyides sivalensis was primarily a C3 grazer, but might have also consumed leaves, tubers, roots, and seeds. The Miocene murine rodents Antemus chinjiensis and Karnimata cf. K. intermedia most likely ate fruits and insects. Among the Plio-Pleistocene murines Cremnomys and Mus cf. Mus flynni were mixed feeders of seeds, grass and insects. Bandicota was a seasonal grazer and mixed feeder, whereas Golunda was primarily a grazer with some intake of seeds and insects. A late Miocene rhinocerotid from Haritalyangar was a C3 grazer, whereas its Plio-Pleistocene relative was a C4 grazer. The hippo Hexaprotodon was a C4 grazer. Plio-Pleistocene giraffid Sivatherium giganteum was a C4 grazer, whereas its close relative Bramatherium was a mixed feeder with its main diet being C4 grass. Camelus was also a mixed feeder with a dominant C4 grass diet. Damalops was a mixed feeder with C4 grass being its principal diet, whereas Hemibos was a C4 grazer. Plio-Pleistocene elephantids Stegodon and Elephas were C3 browsers and C4 grazers, respectively. The Miocene arboreal frugivore/browser primates (sivapithecenes and sivaladapids) that lived in tropical forests were replaced by immigrant terrestrial grazers (baboons) in the Plio-Pleistocene, when the landscape was dominated by savannah type grasslands. On similar lines, Late Miocene monsoon intensification was responsible for the disappearance of several lineages of frugivore/browser suids, tragulids and bovids, which then were later replaced by omnivores/mixed feeders/grazer immigrants. Lineages of rhinos, equids, giraffids, anthracotheres and murids that had a C3 diet in the Late Miocene started adapting to a C4 diet. However, among the proboscideans the Miocene dinotheres (C3 browsers) were replaced by the Plio-Pleistocene elephantids, which were both browsers and grazers.