Diversification of the Family Sporolithaceae: A Case of Successful Survival in the Perspective of Cretaceous–Tertiary Mass Extinctions in India

Abstract

The family Sporolithaceae has recently been separated from Corallinaceae owing to the distinct anatomical characteristics of calcified sori, apical plugs and cruciately arranged spores. By virtue of systematic studies on living as well as fossil specimens at the global level, Sporolithon has been accepted as the generic name for all the species earlier described under Archaeolithothamnion. Fossil record envisages that Sporolithon diversified in India since early Cretaceous. Extensive exposures of marine Cretaceous-Tertiary limestone deposits are known from South, Central, West, North-East India as well as the Andaman-Nicobar Islands that are rich in calcareous algae including species of Sporolithon. Scanty populations of Sporolithon in the present-day tropical regions including India represent a true artifact of a long history of diversification both at the generic as well as family level. Presence of sporolithaceans across the Cretaceous–Tertiary successions in such diverse areas clearly indicate that this family survived the lethal mass extinction at the end of the Cretaceous period and continued its evolution thereafter in the Tertiary. Extraordinarily high diversity in the Danian and Turonian makes Sporolithaceae very likely to stand out as a ‘disaster taxon’. Rapid fluctuations in its diversity across the geological history invite several prospectives pertaining to future research and advancements in the fields of diversity analysis in marine and benthic environment, evolution and geographic distribution.