Two Pune Palaeontologists find ancestry of an Indo-pacific Clam Genus Traced in Kachchh

Pune, September 6, 2019 : Clams belonging to the genus Dosinisca today thrive in the marine waters around New Zealand, Australia and Japan, included in the Indopacific Region. The generic epithet Dosinisca was instituted by William Dall in 1902. In those olden days no information of fossils of this genus was available, and it was taken for granted that this is just amodern genus, and does not have any antiquity. However, Dr.Otukasubsequently found fossils of this clam genus in certain rocks of Japan deposited during the Pleistocene epoch (2.5 million years). Therefore it was presumedthat Dosinisca originated in the Indopacific Region, its antiquity being just 2.5 million years.

Dr.VidyadharBorkar, a visiting faculty in the postgraduate section of the department of Geology in the Fergusson College, Pune and Dr.Kantimati Kulkarni, a Senior Scientist of the Agharkar Research Institute, Pune are studying molluscan fossils from the Miocene Epoch occurring in Kachchh. They found fossils of Dosiniscafrom the sedimentary rocks, which were formed 20 million years ago in the Abdassa Tehsil of Kachchh. What is more, fossil molluscs occurring in the sedimentary rocks of Sindh and Baluchistan Provinces of Pakistan,formed some 5.3 million years ago, were studied by ErnestVredenburg, the noted palaeontologist with the Geological Survey of India. He had published the findings of his study some 90 years ago. The Palaeontologist duo of Pune found that certain clams described by Vredenburg under the name of some othergenus were in reality species of Dosinisca.

During early part of Miocene Epoch, vast expanses in Kathiawar, Kachchh and Sindh were inundated by marine waters as a result of marine transgression around 20 million years ago.These two scientists had already established in a Research communique published earlier, that certain marine animals of the biota, which flourished in this temporary epicontinentalsea, had migrated up to the northwest of Australia at that time through the East Indies and the Timor Island. At about the same time the last phase of uplifting of the Himalayas was completed. Thousands of tonnes of sediment that was being deposited at the bottom of oceanic waters which intervened between the Eurasian Continent to the North and the Indian Peninsula to the South was uplifted and transformed into the loftiest folded mountain range. The habitat of the biota which existed there started shrinking. Very existence of hundreds of genera which merrily thrived there was in jeopardy. Migrating to north was not possible as there was barrier in the form of newly formed Himalayas. To avoid the threat of getting extinct, certain genera managed to migrate towards the East Indies.In course of time their descendants slowly migrated to Indopacific region. In the light of this information, it transpires that the genus Dosinisca evolved in the temporary sea which resulted from the marine transgression in early Miocene times in Kachchh.

The research communique describing fossils of Dosiniscafrom Kachchh and discussing their significance was published in the latest issue of a scientific periodical viz., ‘Journal of Earth System Science’ published by theIndian Science Academy.