Angiosperm pollen assemblages from the Lower Cretaceous (Barremian–lower Aptian) of offshore Saudi Arabia and their implications for early patterns of angiosperm radiation

Early flowering plants constituted a minor component of the Early Cretaceous conifer- and fern- dominated flora. However, their pollen provides a rich, albeit incomplete, record of the group's early evolutionary history. Palynological analysis of Barremian–lower Aptian successions from the Biyadh and Shu'aiba formations in the Arabian Gulf reveals remarkably high angiosperm diversity. While Chloranthaceae, magnoliids, monocots, eudicots, and other “basal” groups represent the bulk of flowering plants, pollen with uncertain affinities is also a significant component of the angiosperm assemblage. Analysis of the palaeobiogeographic distribution of angiosperm pollen during the late Barremian–early Aptian allowed us to discern three groups of angiosperms. The first group, including Clavatipollenites, produced pollen with a near-cosmopolitan distribution. The second group, including Stellatopollis, had a somewhat restricted distribution in northern Gondwana and western Laurasia. The pollen distribution of the third group, which includes Dichastopollenites, is restricted to central and/or northeastern Gondwana. These varied patterns of palaeobiogeographical spread of early angiosperms reflect different migration and colonisation abilities. When compared with coeval palynological successions from other Gondwanan localities, the composition and diversity of the Arabian angiosperm assemblages support early hypotheses on the radiation of angiosperms that identify northeastern Gondwana as one of the most important centres of angiosperm diversification. The following new taxa are described: Splitipollis gen. nov., Splitipollis reticulatus sp. nov., Tucanopollis doylei sp. nov., Pennipollis spinosus sp. nov., Clavamonocolpites woodii sp. nov., and Retimonoporites arabiensis sp. nov.