Fossil pteropods (Thecosomata, holoplanktonic Mollusca) from the Eocene of Assam-Arakan Basin, northeastern India

A small collection of fossil pteropods, including some unidentified species, provisionally referable to the families Limacinidae, Creseidae, and Clioidae (?) is reported from the late Middle Eocene-Late Eocene beds of the Upper Disang Formation exposed near the town of Pfutsero, Phek District, South Central Nagaland (Assam-Arakan Basin, northeastern India). This is the first record of fossil pteropods from this part of India. Although based exclusively on juvenile or incompletely preserved adult shells, documentation of this collection is important from the viewpoint of biostratigraphy as well as palaeoecology. The occurrence of pteropods in the Upper Disang Formation indicates deposition in an open marine basin above the aragonite compensation depth. The combined assemblages of pteropods and previously reported uvigerinid for aminifers from the Upper Disang Formation indicate a palaeobathymetry of similar to 500 m, i.e. upper bathyal zone, and a tropical-subtropical climate.