Broinsonia parca constricta Hattner, Wind & Wise, 1980
Aspidolithus Noël, 1969. This name is not validly published under ICN Art. 35.1 because its type species, Aspidolithus angustus Noël, 1969, is invalid under ICN Art. 9.1 owing to the designation of two holotypes.
From the Latin pollex (thumb) and fossa (ditch, depression), referring to the thumb-like depression produced by the fluted tube cycle in the central part of the coccolith.
Arkhangelskiellids are constructed by a pelaga with three-tier shields and a tube cycle exhibiting fluted features, with a central area spanned by a porous plate pierced by an axial suture and lacking a distal process. The ring of fluting produces a deep depression in the middle of the tube cycle, giving the appearance of raised inner and outer peripheries corresponding to the central area and the distal shield, respectively.
Species of Pollicifossa are distinguished based on overall size, the size of the shield and central area and their ratio, and the number and arrangement of pores.
The fluted tube cycle and the shields exhibit first-order whitish-yellow interference colours, with intensity decreasing towards the periphery, corresponding to the gradual narrowing of the shields. The pelaga shows inclined extinction and length-fast (–) elongation. The central plate displays whitish-grey interference colours.
Pollicifossa differs from Broinsonia and Acaenolithus in possessing a porous plate with axial sutures rather than an axial cross with lateral bars, as found in Broinsonia and Acaenolithus.
Hattner, J. G. & Wise, S. W. 1980. Upper Cretaceous calcareous nannofossil biostratigraphy of South Carolina. South Carolina Geology 24: 41-117.
Noël, D. 1969. Arkhangelskiella (coccolithes Crétacés) et formes affines du Bassin de Paris. Revue de Micropaléontologie. 11: 191-20