First and oldest record of Seebachia bronni, type species of Seebachia (Bivalvia: Astartidae), from the late Tithonian (Jurassic) of Kutch, India, and its palaeobiogeographic and evolutionary implications

Abstract

The present study reports the oldest occurrence of Seebachia bronni Krauss, 1850, the type species of the genus Seebachia, within the Astartidae from the ferruginous oolitic bands of the upper Tithonian (Jurassic) of Kutch, western India. Although Pruvostiella (Eoseebachia), previously known as Seebachia (Eoseebachia), has been reported from the same horizon of Kutch, analyses using quantitative-morphological and morphometrical characters reveal a significant difference between Pruvostiella (Eoseebachia) and Seebachia (Seebachia). Seebachia has been reported in South Africa, Tanzania and Madagascar. Thus, the occurrence of S. bronni in India sheds light on a marine connection among these regions during the late Tithonian. The range of S. aff. bronni in the Oxfordian of Madagascar to S. bronni in the Tithonian of India and Early Cretaceous of South Africa may indicate an evolutionary size increase. A specimen of S. bronni from the Valanginian was the largest in body size and is possibly a distinct species.