Taxonomy and evolution of Paleogene Antarctic and tropical Lophocyrtid radiolarians

摘要

Investigation of three-segmented theoperids through successive stratigraphic levels in Antarctic Paleogene sediment se- quences, and a tropical reference section, resulted in recognition of four groups characterized by different cephalic structures taxonomi- cally treated as the new genera, Aphetocyrtis and Clinorhabdus, the new subgenus Lophocyrtis (Apoplanius), and the previously described subgenus Lophocyrtis (Lophocyrtis) lineage become extinct at the end of the Middle Eocene.