Sphenolithus spinula

Sphenolithus spinula Bergen & de Kaenel in Bergen et al. 2017

Small [4.0-6.0µm] sphenolith, having a three-bladed diminutive apical spine, low lateral cycle and frustum shape proximal cycle with a conical proximal cavity.

The proximal cycle predominates the apical spine and the lateral cycle. The diminutive apical spine shows maximum birefringence at 45° but extinct (dim) at 0°.

Sphenolithus spinula differs from Sphenolithus delphix Bukry, 1973c and Sphenolithus microdephix Bergen & de Kaenel in Bergen et al., 2017 by having a diminutive apical spine whereas the latter species have long well developed apical spines.

Bergen, J. A., de Kaenel, E., Blair, S. A., Boesiger, T. M., Browning, E., 2017. Oligocene-Pliocene taxonomy and stratigraphy of the genus Sphenolithus in the circum North Atlantic Basin: Gulf of Mexico and ODP Leg 154. Journal of Nannoplankton Research 37(2-3), 77-112.

Bukry, D., 1973c. Coccolith stratigraphy, eastern equatorial Pacific, Leg 16, Deep Sea Drilling Project. Initial Reports of the Deep Sea Drilling Project 16, 653-711.