The oldest record of the bivalve Dosinisca Dall and its implications

Abstract

Certain species of Dosinia occurring in the Miocene of Kachchh and the Pliocene of Balochistan in reality belong to the subgenus Dosinisca (Veneridae, Dosiniinae). This subgenus was hitherto known from the Quaternary of the Western Pacific Zoogeographic Province. The present study reveals that the first occurrence of Dosinisca is in the Khari Nadi Formation (Aquitanian) of Kachchh, India. The faunal affinity of the Kachchh Basin with the Alpine–European region through the Tethys fauna until Oligocene came to an end in the Lower Miocene due to the uplifting of the Himalayas. Later, during Lower Miocene, faunal migration took place between Kachchh and the Barrow Island off the northwestern coast of Australia, through the East Indies and Timor Island. After Dosinisca thrived in the Indian Subcontinent during Lower Miocene, the receding of marine waters endangered its very existence in this part of the globe. It somehow survived in Balochistan during Pliocene due to an episode of marine transgression. However, it must have migrated eastwards to the East Indies to be eventually established in the Western Pacific Zoogeographic Province.