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. heteromorphus S. milanetti S. preasii S. belemnos S. pseudoheteromorphus S. conicus S. calyculus S. delphix S. microdelphix S. spinula | ||
![]() | ![]() | ![]() | ![]() | S. predistentus group Middle Eocene and Oigocene sphenoliths with duocrystalline spines and monocyclic base | S. ciperoensis S. distentus S. predistentus S. patifunditus S. bulbulus S. tawfikii S. celsus S. peartiae S. akropodus S. tribulosus S. directus S. avis S. umbrellus S. triangularis S. intercalaris S. obtusus |
![]() | ![]() | 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 |
Taxonomy:
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.
Tags | LITHS: nannolith-radiate, circular, cylindrical, CROSS-POLARS: R-prominent, |
Metrics | Lith size: 4->20µm; |
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 OReferences:
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Sphenolithus compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 18-4-2021
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