Set number: 833

  • Furcatolithus ascella 155 1
  • Furcatolithus ascella 156 2
  • Furcatolithus ascella 158 3
  • Furcatolithus ascella 157 4
    10µm
Furcatolithus ascella, Early Oligocene, DSDP Leg 25, Site 242, Mozambique Channel (Davie Ridge), Indian Ocean

Set number: 834

  • Furcatolithus ascella 198 1
  • Furcatolithus ascella 199 2
  • Furcatolithus ascella 201 3
  • Furcatolithus ascella 200 4
    10µm
Furcatolithus ascella, Early Oligocene, DSDP Leg 25, Site 242, Mozambique Channel (Davie Ridge), Indian Ocean
Final Epithet
Furcatolithus ascella Varol, in prep.
Basionym

Furcatolithus ascella Varol, in prep.

Diagnosis

Species of Furcatolithus Martini, 1965 has a diminutive conical duolithic apical spine and a semi-open umbrella shape proximal cycle with the convex periphery.

Etymology

From Latin ascella, wing - referring to its wing-like proximal cycle.

Description

Medium size [4.0-8.0µm] species of Furcatolithus Martini,1965 having a diminutive duolithic apical spine with an axial c-axis. The duolithic apical spine is cone shape and triangular in the axial section. The proximal cycle is in a semi-open umbrella shape with a convex periphery. The opposite side of the proximal cycle is better seen at 45° and display an axial c-axis.

In crossed-polarised light, the apical spine shows maximum birefringence at 45° but extinct (dim) at 0° [the axial suture between the two helves is better seen at this orientation].

Remarks

Sphenolithus ascella differs from Furcatolithus celsus (Haq 1971) Howe, 2021 by having a semi-open umbrella shape proximal cycle with a convex periphery and a diminutive non-bifurcated apical spine. The latter has a long, often bifurcating apical spine and shallow hollow frustum shape proximal cycle.

References

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.

Haq, B. U., 1971. Paleogene calcareous nannoflora. Parts I-IV. Stockholm Contributions in Geology 25, 1-158.

Howe, R., 2021. Ultrastructure and taxonomy of the family Sphenolithaceae. Journal of Nannoplankton Research 39(1), 29-75.

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