Spinizonocolpites prominatus (McIntyre) Stover & Evans: fossil Nypa pollen, taxonomy, morphology, global distribution, and paleoenvironmental significance

ABSTRACT The fossil species Monosulcites prominatus was described from Early Eocene sediments in Canterbury, New Zealand. It resembles the pollen of the mangrove palm Nypa fruticans. Subsequently, the new genus Spinizonocolpites was proposed with a type species, S. echinatus, which we consider to be a junior synonym of S. prominatus. However, S. prominatus has not always been recognised as the type species, with many authors deferring to the ‘original’ type, S. echinatus. Some 37 species of Spinizonocolpites have been described, though several are undoubtedly synonyms. Many have an affinity to Nypa and the earliest appeared in the Late Cretaceous, especially in northern South America, Africa, India and Borneo. The Indian subcontinent appears to have been the global centre of diversity of Nypa-like species during the Paleocene with a high diversity of Spinizonocolpites species. Nypa was most widespread globally during the Eocene, but the onset of global cooling in the late Middle Eocene resulted in the ultimate range contraction to Northern Australia, the Indonesian Archipelago, the Philippine Islands and China present day. The presence of Nypa pollen in sediment samples indicates a mangrove environment of muddy, slow moving tidal estuaries or rivers influenced by fresh and brackish waters.