LM and SEM analyses of Afropollis, Stellatopollis and Pennipollis from Aptian sedimentary rocks of the Araripe basin (NE Brazil) – and some thoughts what kind of plants they could have been and how they were pollinated

Afropollis jardinus , two fossil species of Pennipollis and nine of Stellatopollis (cf. S. araripensis, S. barghoornii, cf. S. bituberensis, S. dejaxii, S. dubius, cf. S. largissimus, S. limai and two Stellatopollis sp. ) from the Cascata section of the Araripe basin (NE Brazil) are here presented using transmitted LM and SEM. Pollen size, conspicuous sculpture and ornamentation of three pollen taxa imply that they were most likely entomophilous or had a mixed pollination behaviour. Despite their primary entomophily, these pollen taxa have been frequently encountered, generally in many Gondwanan localities and adjacent areas during the late Early Cretaceous. Therefore, it is assumed that their mother plants lived as pioneering speciess within or fringing various aquatic riverine to deltaic ecosystems from which plant organs, such as pollen, fruits or seeds easily could have been transported via water. When comparing with modern plants, the pollen production for these fossil plants was probably in inflorescences: because of small pollen grains it is assumed that the flowers within the inflorescence were small but numerous for the “ Pennipollis plant”, and probably slightly larger for the “ Afropollis plant”. The large to very large pollen of the “ Stellatopollis plant” are assumed to have been produced by much larger flowers, either solitary or arranged in small numbers in inflorescences too. Rapid speciation and adaption of the pollination systems is suggested for Stellatopollis species and probably Pennipollis species, and might explain the high diversity within one locality or sample horizon.