Sphenolithus alatus

Sphenolithus alatus Varol, in prep.

A small sphenolith having a short bouquet shape clustered apical cycle, longitudinally aligned lateral cycle at 0° and a hollow frustum shape proximal cycle with slightly convex periphery creates a conical proximal depression.

From Latin alatus, wing - referring to its wing-like proximal cycle in axial section.

Small species of Sphenolithus has a hollow frustum shape proximal cycle, lateral cycle with short segments and a bouquet shape cluster apical cycle.

The hollow frustum shape proximal cycle creates a conical proximal depression. In the axial section, a deep triangular proximal depression has an obtuse angle at its apex. The outer surface of the proximal cycle is slightly concave.

The opposite side of the proximal cycle is better seen at 45° and displays an axial c-axis.

The three cycles can be better seen in well-preserved specimens at 45° with the help of the gypsum plate.

The short bouquet shape clustered apical cycle with axial c-axis is not forming a true apical spine.

In the polarised light, the low lateral cycle with a tangential c-axis is aligned longitudinally at 0°.

Sphenolithus alatus differs from Sphenolithus abies Deflandre, 1953 ex Deflandre in Deflandre & Fert, 1954, Sphenolithus moriformis (Brönnimann & Stradner, 1960) Bramlette & Wilcoxon,1967 and Sphenolithus apoxis Bergen & de Kaenel in Bergen et al., 2017 by having

- a short bouquet shape clustered apical cycle

- a lateral cycle with longitudinally aligned short segments at 0°

-a proximal cycle with a slightly convex periphery

- a deep conical proximal depression with an obtuse angle

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.

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.

Brönnimann, P., Stradner, H., 1960. Die Foraminiferen- und Discoasteriden-zonen von Kuba und ihre interkontinentale Korrelation. Erdoel-Zeitschrift 76(10), 364-369.

Deflandre, G., 1953. Hétérogénéité intrinsèque et pluralité des éleménts dans les coccolithes actuels et fossiles. Comptes Rendus Hebdomadaires des Séances de l'Académie des Sciences, Paris 237, 1785-1787.

Deflandre, G., Fert, C., 1954. Observations sur les coccolithophoridés actuels et fossiles en microscopie ordinaire et électronique. Annales de Paléontologie 40, 115-176.