Sphenolithus calyculus

Sphenolithus calyculus Bukry, 1985

Sphenolithus elongatus Martini, 1986

Sphenolithus macroacanthos Aubry 2014 nom. subst. pro Sphenolithus elongatus Martini 1986

Medium to large size species of Sphenolithus has a long monolithic looking three-bladed apical spine, lateral cycle and compact proximal cycle.

The lateral cycle is high, and its segments are aligned longitudinally at 0°. A deep calyx developed in the lateral cycle for the insertion of the apical spine.

The apical spine with axial c-axis made up of three longitudinal blades. In cross-polarised, it is extinct at 0° but shows maximum birefringence at 45°.

Sphenolithus calyculus differs from Sphenolithus belemnos Bramlette & Wilcoxon, 1967 and Sphenolithus heteromorphus Bramlette & Wilcoxon, 1967 by having a low compact proximal cycle and a high lateral cycle with a deep calyx. Moreover, in Sphenolithus belemnos, the proximal cycle is elongated along the long axis, and the lateral cycle is reduced.

Aubry, M. -P., 2015. Cenozoic Coccolithophores: Discoasterales. Micropaleontology Press, American Museum of Natural History, New York. pp. 1-400.

Bramlette, M. N., Wilcoxon, J. A., 1967. Middle Tertiary calcareous nannoplankton of the Cipero section, Trinidad, W.I. Tulane Studies in Geology and Paleontology 5, 93-131.

Bukry, D., 1985. Mid-Atlantic Ridge coccolith and silicoflagellate biostratigraphy, Deep Sea Drilling Project Sites 558 and 563. Initial Reports of the Deep Sea Drilling Project 82, 591-603.

Martini, E., 1986. Paleogene calcareous nannoplankton from the southwest Pacific Ocean, Deep Sea Drilling Project, Leg 90. Initial Reports of the Deep Sea Drilling Project 90, 747-761.