Siwalik mammals of the Jammu Sub-Himalaya, India: an appraisal of their diversity and habitats

摘要

The red bed sequence of the Lower Siwaliks around Ramnagar and the Nagrota Formation of the Upper Siwaliks in the Uttarbeni-Parmandal section are the two highly fossiliferous intervals of the Siwaliks of Jammu Sub-Himalaya, India. The Lower Siwalik mammalian fauna of Ramnagar is best represented in its upper 350m interval. Small and medium sized forms, mostly belonging to browsing species, dominate the mammalian assemblage. The Ramnagar fauna represents the Chinji mammalian fauna (Middle Miocene) of the Potwar Plateau, Pakistan. The assemblage indicates a woodland-type ecosystem having substantial forest component and subordinately developed grassy subareas. The mammalian fauna of the Nagrota Formation in the Uttarbeni-Parmandal section, in contrast, exhibits relatively low species diversity, but considerable increase in the mean body size and progressive hypsodonty of the cheek teeth in the herbivores. This becomes more pronounced above the 2.5 Ma old volcanic tuff layers occurring at the middle of the formation. Broadly, a savanna-type ecosystem is indicated by the mammalian communities of Nagrota Formation, which appears to have been dominated by grassland communities above the tuff zone. The above-tuff faunal zone of the Nagrota Formation can be correlated with the Pinjor faunal zone (Plio-Pleistocene) of the Siwalik Hills, Punjab.