Does specialization imply rare fossil records of some benthic foraminifera: Late Palaeocene examples from the eastern Neo-Tethys (Meghalaya, NE India)

Abstract

The palaeoecological characteristics of Late Palaeocene benthic foraminifera from the eastern Neo-Tethyan sediments of Meghalaya, NE India, are poorly understood. The assignment of taxa as generalists or specialists is a fundamental aspect of ecology that is not given sufficient attention in palaeoecological analyses. The first records of Haymanella elongata and Keramosphaera iranica from the Upper Palaeocene carbonate sedimentary rocks outcropping in the East Khasi Hills, Meghalaya, NE India, are documented herein. These species occurred in warm, hydrodynamically energetic shallow-marine environments as indicated by their associations only with grain-supported microfacies and co-occurrence with taxa assumed to have hosted algal endosymbionts including Operculina, Nummulites, Assilina, Orbitoclypeus, and Discocyclina. H. elongata and K. iranica were found in very narrow horizons of the evaluated sections, which was interpreted as indicating specialization to very specific habitats. Rare records of both these benthic foraminifera can be attributed to their specialist behavior that did not allow the populations to persist in fluctuating environments. In comparison to these specialists, more abundant and potential generalist foraminiferal taxa thrived in the region for longer periods. It is deduced that H. elongata and K. iranica migrated to the study area from the Mediterranean regions but did not thrive.