Sphenolithus

Sphenolithus radians Deflandre in Grassé, 1952

Sphenaster Wilcoxon, 1970.

Nannoturbella Brönnimann & Stradner 1960

Calcareous nannofossils consist of concave base and segments spreading from a common origin, producing hexagonal patterns arranged in three cycles (proximal, lateral and apical cycle). The apical cycle can be classified into the following groups:

Well-developed Single Apical Spine: Exemplified by species such as Sphenolithus heteromorphus.

Well-developed Twin Apical Spine: These can be joined along their entire length (e.g., Sphenolithus didymikoryfi) or wholly or partly divergent (e.g., Sphenolithus capricornutus).

Well-developed multiple apical spines are seen in species like Sphenolithus multispinatus.

Clustered Apical Cycle: This can be biconical (e.g., Sphenolithus abies) or resemble a bouquet (e.g., Sphenolithus dissimilis).

Sphenolithus differs from Furcatolithus in that segments are arranged in three cycles, whereas the segments in Furcatolithus are arranged in two cycles.

Optical Properties: The apical spines and the segments of lateral and proximal cycles exhibit parallel (straight) extinctions and length-fast (-) elongation when viewed from the side (Figure 16 in Varol, 2025a).

Species of Sphenolithus are identified based on their overall shape, height, width, and the construction of proximal, lateral, and apical cycles, as well as their ratios.

Species with biconical clustered apical cycle

• Sphenolithus abies Deflandre, 1953 ex Deflandre in Deflandre & Fert, 1954
• Sphenolithus arthurii Bown, 2005
• Sphenolithus bipedis Bergen & de Kaenel in Bergen et al., 2017
• Sphenolithus conicus Bukry, 1971
• Sphenolithus editus Perch-Nielsen in Perch-Nielsen et al., 1978
• Sphenolithus orphanknollensis Perch-Nielsen, 1971
• Sphenolithus spiniger Bukry, 1971

Species with a bouquet of flower-shaped, clustered apical cycles

• Sphenolithus acervus Bown, 2005
• Sphenolithus alatus Varol, in prep.
• Sphenolithus apoxis Bergen & de Kaenel in Bergen et al., 2017
• Sphenolithus bouketo Varol, in prep.
• Sphenolithus chamilos Varol, in prep.
• Sphenolithus compactus Backman, 1980
• Sphenolithus disbelemnos Fornaciari and Rio, 1996
• Sphenolithus dissimilis Bukry and Percival, 1971
• Sphenolithus grandis Haq and Berggren, 1978
• Sphenolithus humilis Varol, in prep.
• Sphenolithus indica Varol, in prep.
• Sphenolithus moriformis (Brönnimann & Stradner, 1960) Bramlette & Wilcoxon, 1967
• Sphenolithus neoabies Bukry & Bramlette, 1969
• Sphenolithus neospiniger Varol, in prep.
• Sphenolithus orthogonio Varol, in prep.
• Sphenolithus paleodissimilis Varol, in prep.
• Sphenolithus paleograndis Varol, in prep.
• Sphenolithus philippinensis Varol, in prep.
• Sphenolithus porrectus Varol, in prep.
• Sphenolithus primus Perch-Nielsen, 1971
• Sphenolithus pseudobouketo Varol, in prep.
• Sphenolithus pseudopuniceus Varol, in prep.
• Sphenolithus puniceus Bergen & de Kaenel in Bergen et al., 2017
• Sphenolithus tintinnabulum Maiorano & Monechi, 1997
• Sphenolithus trigonikos Varol, in prep.

Species with diverging/radiating apical cycle

• Sphenolithus ankathias Varol, in prep.
• Sphenolithus atlanticus Varol, in prep.
• Sphenolithus capricornatus Bukry & Percival, 1971
• Sphenolithus cometa de Kaenel & Villa, 1996
• Sphenolithus didymikoryfi Varol, 2025a
• Sphenolithus multispinatus Maiorano & Monechi, 1997
• Sphenolithus procerus Maiorano & Monechi, 1997
• Sphenolithus perpendicularis Shamrock, 2010
• Sphenolithus quadrispinatus Perch-Nielsen, 1980
• Sphenolithus runus Bown & Dunkley Jones, 2006
• Sphenolithus stellatus Gartner, 1967
• Sphenolithus truaxii Bergen & de Kaenel in Bergen et al., 2017

Species with a monolithic apical spine (having parallel extinction)

• Sphenolithus belemnos Bramlette and Wilcoxon, 1967
• Sphenolithus calyculus Bukry, 1985
• Sphenolithus delphix Bukry, 1973
• Sphenolithus heteromorphus Deflandre, 1953
• Sphenolithus microdelphix Bergen & de Kaenel in Bergen et al., 2017
• Sphenolithus milanetti Maiorano & Monechi 1998
• Sphenolithus preasii Bergen & de Kaenel in Bergen et al., 2017
• Sphenolithus pseudoheteromorphus Fornaciari & Agnini, 2009
• Sphenolithus quasibelemnos Varol, in prep.
• Sphenolithus spinula Bergen & de Kaenel in Bergen et al., 2017
• Sphenolithus anarrhopus Bukry & Bramlette, 1969
  
• Sphenolithus asper Varol, in prep.
• Sphenolithus conspicuus Martini, 1976
• Sphenolithus richteri Bown & Dunkley Jones, 2012
• Sphenolithus villae Bown, 2005

Species with four or more-bladed apical spines

• Sphenolithus pseudoradians Bramlette & Wilcoxon, 1967
• Sphenolithus radians Deflandre in Grassé, 1952

Species with vestigial apical cycle

• Sphenolithus umbrellus (Bukry, 1971) Aubry and Knuttel in Knuttel, 1986

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

Deflandre, G. 1952. Classe des Coccolithophoridés. (Coccolithophoridae. Lohmann, 1902). In: Grassé, P. P. (Ed.), Traité de Zoologie. Masson, Paris. 439-470.

Martini, E. 1965. Mid-Tertiary calcareous nannoplankton from Pacific deep-sea cores. Colston Papers 17: 393-411.

Wilcoxon, J. A. 1970. Sphenaster new genus, a Pliocene calcareous nannofossil from the tropical Indo-Pacific. Tulane Studies in Geology and Paleontology 8: 78-81.