Wigginsiella n. gen., Spongodinium, and Apteodinium as members of the Aptiana-Ventriosum complex (fossil Dinophyceae)

Abstract Well‐preserved representatives of three genera of fossil gonyaulacoid dinoflagellate cysts, Wigginsiella n. gen., Spongodinium Deflandre 1935, and Apteodinium Eisenack 1958, show paratabulation details that indicate a close relationship to genera referred to the "Aptiana‐Ventriosum complex”; of Helenes (1986) and the "Danea group”; of Damassa (1984). Important details of paratabulation include: (1) asymmetrical, oblong, antapical paraplate (Y), (2) elongate posterior intercalary (X), (3) crescentic posterior sulcal (Z), (4) pentagonal‐hexagonal last precingular (li) which contacts both first and fourth apicals (lu and A), (5) offset of alignment of the parasutures of the dorsal precingular and dorsal postcingular paraplates (offset of IV/V and 4/5), and (6) contact of the second and fourth apicals (B and A) precluding contact of P with the third apical (C). Expression of paratabulation in species of these three genera is typically subtle and unclear in many specimens, thus other criteria, such as...