Owenia hillii Crux, 1991
Owenia is a holococcolith characterized by a prominent solid distal process that either tapers or remains parallel-sided and terminates with a plug. Complete Owenia specimens naturally settle in a side-view position. In the plan view, the base of Owenia consists of a narrow rim with projections along the short axis and two blocks. Owenia exhibits inclined extinction with length-slow (+) elongation.
Distinguishing Owenia from Isocrystallithus and Sarmania lies in its inclined extinction, whereas Isocrystallithus and Sarmania exhibit parallel extinction. When comparing side views, Owenia differs from Kahvecia and Swapansahooia: Owenia’s solid distal process terminates with a plug and is raised from two struts aligned with the short axis of the base. In contrast, Kahvecia has a very narrow solid distal process, while Swapansahooia boasts a hollow distal process with a sombrero-like termination.
Lastly, in the plan view, Owenia reveals a rim with two projections along the short axis, surrounding two blocks aligned along the long axis. Kahvecia, on the other hand, lacks any projections on its rim and features four blocks. Meanwhile, Swapansahooia presents a rim, four blocks, and a central opening surrounded by struts.
Crux, J. A. 1991. Albian calcareous nannofossils from the Gault Clay of Munday’s Hill (Bedfordshire, England). Journal of Micropalaeontology. 10: 203-221.