(Kamptner 1937) Paasche in Markali & Paasche 1955 [Coccolithus]
Heterococcoliths Incertae Sedis
After Young et al. 2003. Coccospheres sub-spherical. Liths convex distally; distal surface with pattern of ridges; major ridges sub-radial running along sutures; secondary ridges diverge anticlockwise from them.
Tropical - sub-tropical (Findlay & Giraudeau, 2000).
Between 57°12' S, 155°23'E and 58°49' S, 152°48'E, L. Harding, AAD, unpub.
Variation: The morphology of this species is very variable, in terms of the ridge thickness, presence of papillae (nodes) on the ridges, number of secondary ridges, degree of bimodality in ridge thickness. Kleijne (1993) distinguished several types of U. tenuis. This work has not been followed up by a detailed study and these types are arguably intergradational. Nonetheless, most specimens are readily assignable to a single type so it seems possible that they will prove to be discrete (sub) species.
Type I - coccoliths with distinct sutural ridges and numerous finer papillate secondary ridges.
Tyep II - sutural and secondary ridges papillate.
Type IIIa - sutural and secondary ridges heavily calcified and not clearly separable. Central area closed by inward extensions of the sutural rides.
Type IIIb - sutural and secondary ridges heavily calcified but well-separated, 2-4 secondary ridges per element. Central area open.
Type IV - sutural ridges well calcified near centre of coccolith, lower toward periphery. Numerous secondary ridges, often anastamosing.