Abstract

Detailed examination of inner shelf sediments of the Bay of Bengal, off Karikkattukuppam, south-east coast of India near Madras, revealed quite a few rarely recorded or hitherto unidentified taxa. Of these, one species is a living representative of the genus Cocoarota Loeblich and Tappan, considered to be extinct since the Eocene. The few existing records of this genus from the Upper Eocene, exclusively from the American region, and lack of subsequent ones, raise questions with regard to its geographical distribution and possible migration since the Eocene.

Cocoarota madrasensis n. sp. Rajeshwara Rao and Revets is a calcareous, densely perforate (except for the apertural face and sutures), foraminifer characterized by the presence of a series of irregularly shaped bosses clustered in the depressed umbilical area, resembling spiralized ornamentation as a result of thickening of folia and inner ends of sutures of earlier whorls. The flaps or folia on the umbilical side hover over the umbilical aperture that remains open in the earlier parts of the test. It is one of the more abundantly occurring species on the inner shelf off Madras (now Chennai), associated with considerable numbers of Asterorotalia trispinosa (Thalmann) and A. inflata (Millett), particularly at depths between 38 and 55 m, and on substrate with relatively higher mud content. The present discovery necessitates not only extension of the stratigraphic range of the genus Cocoarota but also a thorough review of the existing literature.

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