Set number: 841

  • Furcatolithus celsus 1952 1
  • Furcatolithus celsus 1951 2
  • Furcatolithus celsus 1949 3
  • Furcatolithus celsus 1950 4
    10µm
Furcatolithus predistentus, Early Oligocene, DSDP Leg 25, Site 242, Mozambique Channel (Davie Ridge), Indian Ocean
Final Epithet
Furcatolithus predistentus (Bramlette & Wilcoxon, 1967) Howe, 2021
Basionym

Sphenolithus predistentus Bramlette & Wilcoxon, 1967

Synonyms

Sphenolithus tribulosus Roth, 1970

Description

Furcatolith has a shallow hollow conical frustum shape proximal cycle and a long apical spine broadening at the proximal end. The cone shape duolithic apical cycle has a flat base. The height of the apical spine varies greatly and may have various length bifurcation distally.

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

The shallow, empty frustum shape proximal cycle has a much narrower diameter than the diameter of the apical spine at its base.

Remarks

Furcatolithus predistentus differs from all other species of Furcatolithus Martini, 1965 by a distinct broadening of the apical spine at its base. It is further distinguished from all other Furcatolithus species by having a proximal cycle with a much narrower diameter than the diameter of the apical spine at its base.

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.

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.

Roth, P. H. 1970. Oligocene calcareous nannoplankton biostratigraphy. Eclogae Geologicae Helvetiae 63: 799-881.