NEW FINDING OF TRIGONIOIDES BIVALVE IN THE DECCAN INTERTRAPS OF MADHYA PRADESH, INDIA AND ITS STRATIGRAPHIC IMPLICATIONS

Deccan traps of India is one of the largest volcanic provinces on the earth. Besides, its various volcanogenic structures like columnar joints, pillow and amygdaloidal structures, it is also characterized by the presence of sedimentary units which are generally known as intertrappean beds that often contain both vertebrate and invertebrate fossils, essentially mollusca. Very recently, small bivalve specimens belonging to Trigonioides have been discovered in various locations, i.e. Deori, Karondi and Barga, located about 100 kms away from Jabalpur in Madhya Pradesh, India. This unreported genus is a new addition to the biodiversity of mollusca during Deccan volcanic episode. Bivalves of the Superfamily Trigonioidea is an Unioform bivalve and are characterized by separated anterior adductor and anterior pedal retractor muscle scars and an ornament which typically comprises chevron forming ribs. Certain biocharacters of this bivalve are characteristic in different taxonomic levels. Muscle scar diagnosis help to identify superfamily, general ornamentation pattern at the family and subfamily level, radial ribs including the VA (angle of V shaped ribs) and hinge teeth at the generic and subgeneric level.

Systematic Paleontology

Order Trigoniida Dall, 1889

Superfamily Trigonioidea Cox, 1952

Family Trigoniodidae Cox, 1952

Subfamily Trigoniodinae Cox, 1952

Genus Trigonioides Kobayashi and Suzuki, 1936

Trigonioides hislopensis n.sp

The finding of Trigonioides, for the first time in these Intertrappean horizons, indicates that the age of the intertrappeans in those localities to be Upper Cretaceous, as the LAD of this genus is Upper Cretaceous, throughout the world.