The oldest birotule-bearing freshwater sponges from the Upper Cretaceous–lower Paleocene Deccan volcanic-associated sediments of India

A new fossil occurrence of freshwater sponges (Porifera: Demospongiae) is reported from the Deccan volcanic associated Naskal intertrappean locality, deposited in an interval of <100 kyr across the Cretaceous/Paleogene (K/Pg) boundary. This is the oldest record of siliceous fossil birotule spicules (gemmuloscleres) belonging to asexual resting stages typical of the order Spongillida. The analysis supports the ascription of these fossils to the family Palaeospongillidae. The diagnosis and description of Longibirotula Pronzato and Manconi gen. nov. and its type species Longibirotula antiqua Manconi and Samant sp. nov. from the Naskal intertrappean is based on skeletal and gemmular spicular morphotraits. The findings have provided evidence of the presence of diversified groups of freshwater sponges during the Late Cretaceous on the Indian subcontinent and Gondwanaland. From the biogeographic context, the findings track the evolutionary trends of the oldest continental sponges in the Asian and Australasian/Insular Pacific regions.