Integrated Transmitted Light Microscope (TLM), Confocal Laser Scanning Microscope (CLSM), and Scanning Electron Microscope (SEM) studies reaffirm the long-debated taxonomic status of Parasaccites Bharadwaj et Srivastava 1964 as a junior synonym of Cannanoropollis Potonié et Sah 1960

Abstract

Despite several workers re-emphasizing the taxonomic status of the Pennsylvanian–Permian (late Paleozoic) cordaitalean morphogenus Parasaccites as a junior synonym of Cannanoropollis, Parasaccites is still in use, especially in India. Therefore, to resolve this discrepancy and re-affirm if Parasaccites merits a generic status or must be considered as a junior synonym of Cannanoropollis as claimed, we took up this work for a detailed study comprising of an extensive review of the older systematic works, re-examination of illustrated specimens and slides of available holotypes/paratypes of both the genera under Transmitted Light Microscope (TLM), Confocal Laser Scanning Microscope (CLSM), and Scanning Electron Microscope (SEM). They were also compared with specimens of palynological materials collected from the Koel-Damodar and Wardha-Godavari Basins in India and South American Basins (Bolivia, Argentina, Brazil, and Uruguay). The materials analysed correspond to different stages of the full-acid treatment, including oxidation, and were mounted on slides to observe their effects on grain morphology. The morphological features re-examined were amb, corpus, nature of the saccus, and diameter, all of which showed no apparent differences between the two genera. The nature of the zone of attachment, which was considered the main distinguishing character despite its difficulty to interpret, especially in poorly preserved or oxidized specimens, was not mentioned in the original diagnosis of Canannoropollis. This feature was mentioned in later works and observed in our present study, in which well-preserved specimens displayed different zones of saccus attachment, ranging from subequatorial proximal and distal attachment to proximally equatorial–subequatorial to distally subequatorial attachment, sometimes with a diffuse transition. Therefore, we emended the original diagnosis of Cannanoropollis to incorporate the possible attachment zones. The remaining features of Parasaccites overlap with those of Canannoropollis and thus do not warrant a generic status for it. Hence, this work reaffirms that Parasaccites is a junior synonym of Canannoropollis, and by the nomenclatural rule of priority, its further use should be avoided. The remaining species erected under Parasaccites have been synonymized with the convalidated species of Cannanoropollis based on their original or emended diagnoses, viz., C. janakii, C. densus, and C. triangularis. Meanwhile, some bilateral species erected under Parasaccites have been transferred to other genera, such as Caheniasaccites and Potonieisporites, because they differ from Cannanoropollis, which bears a radial amb.