Earliest Pellatispira Boussac from the middle Eocene of India: morphological speciality of the ancestral stock

Abstract

Pellatispira Boussac, known to be restricted to Upper Eocene shallow marine sediments of the Tethyan and Indo-Pacific provinces, has been recovered together with Assilina papillata Nuttall, Assilina cancellata Nuttall, Nummulites atacicus Leymerie and Orbulinoides beckmanni (Saito) in a thin marl bed in the Amravati River section near Bharuch, Western India. The assemblage occurs in the Globigerapsis beckmanni Zone of Middle Eocene age. Represented by Pellatispira crassicolumnata Umbgrove, P. orbitoidea (Provale), P. aff. madaraszi (Hantken) and P. boussaci sp. nov., the genus of the Middle Eocene is distinct with its primitive state of some characters, including the presence of discontinuous longitudinal canals in the outer whorl wall, irregular growth of radial canals in the marginal crest and low trochospiral coiling. Externally it possesses heavy ornamentation like its Late Eocene descendants. The wall structure and the general structure of the tests of this primitive Pellatispira permit its inclusion within the Pellatispiridae.