Nannotax Enabling nannofossil research

Description: Coccosphere compact. Coccoliths circular with narrow central opening narrow; sutures on distal shield strongly kinked. Proximal shield bicyclic, concave, smaller than distal shield. A few  hook-shaped protrusions are often present in the central opening.

Remarks: This taxon was regarded as a variety of U. sibogae (U. sibogae var. foliosa) but there are strong morphological differences between U. sibogae and U. foliosa and cultures of the two species maintain their respective morphologies (Geisen et al. 2004). Molecular genetic data indicates that they are sibling species and suggests a divergence in the Miocene (Sáez et al. 2003).

Range: NN16? to 21, probably evolves from U. jafari in the Pliocene. SEM below, from the Early Miocene is a rather clear U.foliosa specimen from a sample set also with unambiguous U. jafari and U. rotula.