Himalayan Geology, Vol. 42 (1), 2021, pp. 137-154, Printed in India

Morphometry and morphology of Testate amoebae from the Miocene sub Himalayan zone of Darjeeling, India

ANJUM FAROOQUI, HUKAM SINGH*, MAHESH PRASAD, VEERU KANT SINGH

Birbal Sahni Institute of Palaeosciences, 53 University Road, Lucknow, India

*Email (Corresponding author): hukams@gmail.com

Abstract: The records of oldest testate amoebae have been reported from the Permian period in the Indian sub-continent and there is dearth of knowledge from younger epochs. Present work reports the diversity and morphometry of testate amoeba observed in the Middle Siwalik claystone deposited during the upper Miocene, Darjeeling, West Bengal.  Total 30 species of the testate amoebae were recorded in the studied samples which belonged to eight Families. These are Arcellidae (9 species), Centropyxidae (7 species) Difflugiidae (8 species), Trigonopyxidae (3 species) and one each of Heleoperidae, Padaungiellidae, Hyalospheniidae  and Nebelidae. Among these, 17 species are new to the Miocene epoch which were not recorded from the older Permian deposits in North-western Himalaya of India. These are- A. excavata, A. catinus, C. aerophila 'sphaginicola', C. corona, C. delicatula, D. baccillifera, D. curvata, D. acutissima, D. varians, Padaungiella lageniformis, Cucurbitella tricuspis, Nebela aliciae, Cyclopyxis kahli, C. eurystoma, Trigonopyxis arcula, T. minuta and Awerintzewia cyclostoma. Few Arcella species having protruded pseudostome were recorded unlike the known species having invaginated pseudostome. The conducive humid habitat (mean annual temperature of 23-27°C and precipitation > 200cm) and the land connections/species migration during the Miocene between the Indian subcontinent and adjoining Eurasia perhaps resulted in the diversification of these protists in the North-eastern India.

Keywords: Testate amoebae, Miocene, Middle Siwalik, Darjeeling, Palaeoclimate.