Classification: ntax_cenozoic -> Discoasterales -> Sphenolithaceae -> Sphenolithus
Sister taxa: Sphenolithus

Daughter taxa (time control age-window is: 0-800Ma)Granddaughter taxa
S. capricornutus group
Apical spine formed of radiating elements

S. dissimilis group
Bases cylindrical or conical, compound apical spine

S. moriformis group
Conical and hemispherical sphenoliths without prominent apical spines.

S. heteromorphus group
Late Oligocene - Early Miocene sphenoliths with apical spines formed from a single element.

S. predistentus group
Middle Eocene and Oigocene sphenoliths with duocrystalline spines and monocyclic base

S. furcatolithoides group
Small Middle Eocene sphenoliths with duocrystaline spines that are dark in the 45° position.

S. radians group
Eocene to Early Oligocene sphenoliths with compound spines, that are visible but dim at 0° and brightest when at 45° to the polarizing directions.

S. conspicuus group
Late Paleocene and Early Eocene sphenoliths with monocrystalline spines

Sphenolithus sp.
Specimens which cannot be assigned to established species


Citation: Sphenolithus Deflandre in Grassé, 1952
Rank: Genus
Type species: Sphenolithus radians Deflandre in Grassé, 1952
Taxonomic discussion: More than 40 species of Sphenolithus have been described. We subdivide them here into informal groups which we believe represent clusters of closely related species, or in some cases single morphologically variable species. The primary criteria are the nature of the spine which may be barely developed (moriformis group), formed of numerous elements (radians group), two elements (predistentus and furcatolithoides groups), or a single element (conspicuus and heteromorphus groups). In addition the base may be formed of several cycles of elements (most groups) or only one cycle (predistentus group).
There has been a tendency toward recognition of ever more sphenolith "species", but it is by no means clear that these reflect biological species, as discussed by Towe (1979). 
See also - Perch-Nielsen 1985; Aubry 1989; Maiorano & Monechi 1997.

Distinguishing features: Conical nannoliths with a concave base, consisting of a mass of elements radiating from a common origin.

Farinacci & Howe catalog pages: Sphenolithus * , Furcatolithus * , Sphenaster * , Nannoturbella *

Morphology: Sphenolith structure: The individual elements of sphenoliths are elongated parallel to their c-axis (this is clear from light microscopy), and consist of three lath-like blades arranged in a Y-shaped form. This morphology is visible in SEMs of specimens from samples with very good preservation, or slight etching. With overgrowth the spaces between the segments become infilled and the elements develop a spinose form. The triple lath form is probably related to the trigonal symmetry of calcite, with laths developing parallel to the x-axes.
The elements radiate from a single origin, which gives the sphenoliths a compact form, and a clear extinction-cross, in polarized light. The proximal part of all sphenolith species is composed of a single cycle of 8 to 16 of these elements. The axes of the proximal elements slope down from the median plane. A concave base is formed by laths from adjacent elements meeting.
The upper half of sphenoliths is normally formed of two or three cycles of elements, radiating from the centre, at decreasing angles to the vertical. The details of the structure are, however, variable; particularly toward the apex, which gives rise to a large amount of species level variation.

Search data:
TagsLITHS: nannolith-radiate, circular, cylindrical, CROSS-POLARS: R-prominent,
MetricsLith size: 4->20µm;
The morphological data given here can be used on the advanced search page. See also these notes

Geological Range:
Last occurrence (top): near base of Piacenzian Stage (14% up, 3.5Ma, in Piacenzian stage). Data source: Total of range of species in this database
First occurrence (base): near top of Danian Stage (90% up, 62.1Ma, in Danian stage). Data source: Total of range of species in this database

Plot of occurrence data:


Aubry, M. -P. (1989a). Handbook of Cenozoic calcareous nannoplankton. Book 3: Ortholithae (Pentaliths, and others), Heliotithae (Fasciculiths, Sphenoliths and others). Micropaleontology Press, American Museum of Natural History, New York. 1-279. gs

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

Maiorano, P. & Monechi, S. (1997). New Early Miocene species of Sphenolithus Deflandre, 1952 from the North Atlantic Ocean. Journal of Nannoplankton Research. 19(2): 103-107. gs V O

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

Perch-Nielsen, K. (1985a). Cenozoic calcareous nannofossils. In, Bolli, H. M., Saunders, J. B. & Perch-Nielsen, K. (eds) Plankton Stratigraphy. Cambridge University Press, Cambridge 427-555. gs

Towe, K. M. (1979). Variation and systematics in calcareous nannofossils of the genus Sphenolithus. American Zoologist. 19: 555-572. gs

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


Sphenolithus compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 5-8-2021

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Short stable page link: https://mikrotax.org/Nannotax3/index.php?id=1277 Go to Archive.is to create a permanent copy of this page - citation notes

Comments (1)

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Kenneth M. Towe (Smithsonian Institution emeritus, US)
This old paper should be added to the list of references...

1979 K.M. Towe, Variation and systematics in calcareous nannofossils of the genus Sphenolithus. AMERICAN ZOOLOGIST, v. 19, p. 555-572.

It should give pause to the discussion of various "species" in this genus.
Jeremy Young (UCL, UK)
good point - do you have a pdf copy of the paper. it would be nice to include your reconstruction of sphenolithus sphere.
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