Diversity of araucariacean pollen from the Lower Cretaceous Rio da Batateira and lower Crato formations (Araripe basin, SE Brazil), based on micromorphology of the ektexine using SEM

Here we demonstrate the micro-morphological variety of Aptian pollen grains affiliated with Araucariaceae s.l. with the LM and SEM. We could distinguish five micromorphological groups and in addition to well known araucariacean pollen taxa such as Araucariacites spp., Balmeiopsis and Callialasporites spp., we could also assign Exesipollenites scabratus, E. cf. tumulus, and one Inaperturopollenites taxon as araucariacean. Using LM, a hidden diversity of micromorphological features are missed within the four pollen taxa (“Araucariaceae” sp. 1 to sp. 4) that are similar to the morphogenus Araucariacites demonstrating the importance of using scanning electron microscopy in palaeopalynology. Pollen characterized by micromorphological features of group 4 comprises Callialasporites spp., Inaperturopollenites sp. and “Araucariaceae” sp. 1 and are assumed to be dispersed equivalents of previously described eurypalynous pollen cones. These pollen cones and pollen grains might represent an ancient group of Araucariaceae with overlapping characters from Podocarpaceae and Araucariaceae. In total 15 Araucariaceae pollen taxa are present in the Rio da Batateira and lower Crato formations, a number that exceeds the diversity of previously described araucariacean macrofossils and pollen of the Araripe basin. These results are evidence that despite the rapid evolution of angiosperms in the Early Cretaceous, gymnosperms, particularly Araucariaceae, still played an important role in various ancient vegetation habitats. • The Aptian/Albian succession is in the Araripe Basin, Brazil. • Fossil Araucariaceae pollen taxa (15) were far more diverse than expected. • SEM investigation revealed 5 micromorpholoical groups. • Inaperturopollenites and Exesipollenites species are affiliated with Araucariaceae