S. furcatolithoides group


Classification: Coccolithophores -> Discoasterales -> Sphenolithaceae -> Sphenolithus -> S. furcatolithoides group
Sister taxa: S. capricornutus group, S. dissimilis group, S. moriformis group, S. heteromorphus group, S. predistentus group, S. furcatolithoides group, S. radians group, S. conspicuus group, S. sp.,

Daughter taxa: (blue => in age window 0-800Ma)
forms with low basal quadrants (‘feet’) and ~90° bifurcations
Spines diverge just above the base and are near-parallel in the lower part
square base with 3 or 4 spines
square base with two spines that diverge by around 90°
tapering base with narrow, high-angled lateral spines;
duocrystalline spines that bifurcate high-up on the spine.

Taxonomy:

Citation: Sphenolithus furcatolithoides group sensu Bown & Dunkley Jones, 2012
Rank: species group

Distinguishing features: Small Middle Eocene sphenoliths with duocrystaline spines that are dark in the 45° position.

Farinacci & Howe catalog pages:


Morphology remarks: Included within the S. radians group by Bown & Dunkley Jones (2012), these species are characterised by two (rarely more) bifurcating apical spines, bright at 0° and dark at 45°, extending from the upper quadrants. Species differentiation is based on the height and angle of spine bifurcation and size of the basal quadrants. In moderate to poor preservation the upper portion of these tall spines is usually lost, but when well preserved, as seen herein, the entire lith may be preserved, highlighting the extreme spine lengths (up to 25μm; Pl. 11, fig. 25) and variations in upper spine morphology. In the slightly younger, and probably descendant, S. predistentus group, only the lower quadrants are clearly discernable in the basal column and the spines are bright at 45° and diverge in the uppermost part of the spine (e.g. S. obtusus, S. runus, S. predistentus). [Bown & Newsam 2017]

Search data:
TagsLITHS: N: 3D-radiate, conical,
CSPH: not known, V-UNITS: none, R-UNITS: lower-tier, spine, DETAILS: isogyres radial,
MetricsLith size: 2->17µm;
Sources:
The morphological data given here can be used on the advanced search page. See also these notes

Geological Range:
Last occurrence (top): in lower part of Bartonian Stage (22% up, 40.4Ma, in Bartonian stage). Data source: Total of range of species in this database
First occurrence (base): at base of Lutetian Stage (0% up, 47.8Ma, in Lutetian stage). Data source: Total of range of species in this database

Plot of occurrence data:

References:

Bown, P. R. & Dunkley Jones, T. (2012). Calcareous nannofossils from the Paleogene equatorial Pacific (IODP Expedition 320 Sites U1331-1334). Journal of Nannoplankton Research. 32(2): 3-51. gs :: view :: open


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S. furcatolithoides group compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 12-7-2020

Taxon Search:
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Short stable page link: http://mikrotax.org/Nannotax3/index.php?id=1213 Go to Archive.is to create a permanent copy of this page - citation notes



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