Sphenolithus multispinatus

Sphenolithus multispinatus Maiorano & Monechi, 1997

Medium to large size (5.0-9.0µm) species of Sphenolithus Deflandre in Grassé,1952 having a frustum shape proximal cycle in the various height, reduced lateral cycle and gently diverging long apical spines made up of three or more long segments. In the side view, all the segments of the apical spine with axial c-axises show maximum birefringence at 45°, whereas only two outer segments show maximum birefringence at 0°. The lateral cycle is more distinct at 45°, where the proximal cycle is extinct (dim).
Two variants of the proximal cycle were noted; short wide, and relatively high elongated.

Sphenolithus multispinatus differs from Sphenolithus cometa de Kaenel & Villa, 1996 by having apical spines with greater outward divergence and frustum shape lateral cycle.

de Kaenel, E., Villa, G., 1996. Oligocene-Miocene calcareous nannofossil biostratigraphy and paleoeecology from the Iberian Abyssal Plain. Proceedings of the Ocean Drilling Program, Scientific Results 149, 79-145.

Maiorano, P., Monechi, S., 1997. New Early Miocene species of Sphenolithus Deflandre, 1952 from the North Atlantic Ocean. Journal of Nannoplankton Research 19(2), 103-107.