Sphenolithus furcatolithoides

Locker, 1967 May 12, 2021

Set number: 950

  • Sphenolithus furcatolithoides 25812 1
  • Sphenolithus furcatolithoides 25803 2
  • Sphenolithus furcatolithoides 25815 3
  • Sphenolithus furcatolithoides 25817 4
  • Sphenolithus furcatolithoides 25813 5
  • Sphenolithus furcatolithoides 25802 6
  • Sphenolithus furcatolithoides 25821 7
  • Sphenolithus furcatolithoides 25820 8
  • Sphenolithus furcatolithoides 25805 9
  • Sphenolithus furcatolithoides 25806 10
  • Sphenolithus furcatolithoides 25811 11
  • Sphenolithus furcatolithoides 25810 12
    10µm
Sphenolithus furcatolithoides, Middle Eocene, IODP Leg 171, Site 1051A, Black Nose, Western North Atlantic
Final Epithet
Sphenolithus furcatolithoides Locker, 1967
Basionym

Sphenolithus furcatolithoides Locker, 1967

Synonyms

Sphenolithus furcatolithoides labradorensis Firth,1989

Sphenolithus cuniculus Bown, 2005d

Description

Species of Sphenolithus Deflandre in Grassé, 1952 have a low frustum shape proximal cycle with a conical proximal cavity, a very low lateral cycle [can only be seen using a gypsum plate at 45°] and a bifurcated duolithic apical spine with an inclined extinction.

The bifurcated duolithic apical spine with an axial median line shows maximum birefringence at 0° and extinct (dim) at 45° (inclined extinction-optic axes are not parallel to the crystallographic axis].

The bifurcation of the apical spine can start at a different distance from lateral elements.

Remarks

Sphenolithus furcatolithoides differs from Furcatolithus obtusus, (Bukry, 1971b) Howe, 2021 by having a very low lateral cycle and a bifurcated apical spine with an inclined extinction (45°). The latter is lacking a lateral cycle and has a non-bifurcated apical spine with an oblique extinction (22°).

Sphenolithus furcatolithoides labradorensis Firth (1989) is identified based on where the bifurcation started. This is a very subjective criterion to adopt.

Sphenolithus cuniculus Bown, 2005d is identified by having very low proximal and lateral cycles and a broader apical spine. We believe it is a preservational morphotype of Sphenolithus furcatolithoides.

References

Bown, P. R., 2005d. Palaeogene calcareous nannofossils from the Kilwa and Lindi areas of coastal Tanzania (Tanzania Drilling Project 2003-4). Journal of Nannoplankton Research 27(1), 21-95.

Bukry, D., 1971b. Cenozoic calcareous nannofossils from the Pacific Ocean. - San Diego Society of Natural History Transactions 16, 303-327.

Firth, J. V., 1989. Eocene and Oligocene calcareous nannofossils from the Labrador Sea, ODP Leg 105. Proceedings of the Ocean Drilling Program, Scientific Results 105, 263-286.

Locker, S., 1967. Neue Coccolithophoriden (Flagellata) aus dem Alttertiär Norddeutschlands. Geologie, Berlin 16, 361-364.

Taxonomy
Sphenolithus
Biostratigraphy
  • Phanerozoic
    • Cenozoic
      • Paleogene
        • Eocene
          • Late Eocene
          • Middle Eocene
            • Bartonian
            • Lutetian
Stratigraphic Range
Lutetian - Bartonian
Age (Ma)
46.07 - 40.80
Holotype
Sphenolithus furcatolithoides 25803 Sphenolithus furcatolithoides 25803

Sphenolithus furcatolithoides Locker, 1967

Late Eocene

Nennhausen Borehole 2/63, Northern Germany