Fossil leaves of Pandanaceae from India suggest Paleogene persistence of the family in South Asia

Abstract

Pandanaceae (the screw-pine family) represents an early-diverging monocot lineage with a predominantly paleotropical distribution, yet its fossil record remains sparse and uneven, particularly in South Asia. Here, we report well-preserved fossil leaves attributable to Pandanites trinervis (Ettingsh.) J. Kvaček et A.B. Herman, from the late Oligocene Tikak Parbat Formation of the Makum Coalfield, Assam, India. The fossils are characterized by elongate linear laminae having a distinctive M-shaped transverse section with midvein (1°), uniformly developed 2° parallel veins of the same width, transverse veins (3°) obliquely to perpendicularly oriented, and well-developed marginal prickles, a combination of characters diagnostic of Pandanaceae. This record constitutes macrofossil evidence of pandanaceous leaves from the Indian Paleogene and bridges a critical temporal and geographic gap between Late Cretaceous Laurasian occurrences and younger Cenozoic tropical records of the family. The Makum fossils suggest Paleogene persistence and ecological continuity of Pandanaceae across the paleotropics prior to their Neogene diversification and temporally coinciding with molecularly inferred diversification of extant Pandanus lineages in the late Eocene–Oligocene. Sedimentological, palynological, and CLAMP-based paleoclimatic data indicate deposition in warm, humid, lowland deltaic environments dominated by freshwater swamps, riparian corridors, and evergreen forests, closely matching the ecological preferences of extant Pandanaceae. These findings underpin the role of the Indian subcontinent as an important region of persistence for pandanaceous lineages during the Paleogene and provide new insights into the biogeographic history of the family in tropical Asia.