S. heteromorphus group


Classification: ntax_cenozoic -> Discoasterales -> Sphenolithaceae -> Sphenolithus -> S. heteromorphus 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.

species arranged in stratigraphic order, youngest at top (time control age-window is: 0-800Ma)
S. heteromorphus & variants
Sphenolithus heteromorphus
Apical spine very well-developed. Lateral elements nearly as large as proximal elements.
Sphenolithus milanetti
Large; proximal shield wide and high; apical spine slightly extended & made up of a single crystal unit
Sphenolithus preasii
Transitional to S. milanetti - base well-eveloped, convex lower surface, shouldered profile.
S. belemnos
Sphenolithus belemnos
Dart-shaped, apical spine well-developed. Lateral elements much smaller than proximal elements.
earlier species
Sphenolithus pseudoheteromorphus
Similar to S. heteromorphus but base has more elements including a few almost parallel with the spine; spine slightly asymmetric
Sphenolithus conicus
Large, coarsely constructed with high, gently tapering base and short tapering spine that is dark at 0° and bright at 45°.
Sphenolithus calyculus
Small sphenolith with long apical spine and compact base.
S. delphix and variants
Sphenolithus delphix
Large (>8µm) sphenolith with single long apical spine and flaring proximal cycle.
Sphenolithus microdelphix
Like S. delphix, but smaller (<8 µm)
Sphenolithus spinula
Like S. delphix, but smaller (<8 µm) and with short spine

Taxonomy:

Citation: Sphenolithus heteromorphus group
Rank: species group

Distinguishing features: Late Oligocene - Early Miocene sphenoliths with apical spines formed from a single element.

Farinacci & Howe catalog pages:


Morphology: The spines go into extinction as a single unit when they are aligned with the polarisation directions

Search data:
TagsLITHS:
MetricsLith size: 4->20µm;
The morphological data given here can be used on the advanced search page. See also these notes

Geological Range:
Notes: S. heteromorphus and S. belemnos are common species and key biostratigraphic markers. S. delphix, S. capricornutus and S. calyculus are a group of relatively rare small species with well-developed apical spines characteristic of the Earliest Miocene.
Last occurrence (top): near base of Serravallian Stage (13% up, 13.5Ma, in Serravallian stage). Data source: Total of range of species in this database
First occurrence (base): in upper part of Rupelian Stage (74% up, 29.6Ma, in Rupelian stage). Data source: Total of range of species in this database

Plot of occurrence data:

References:


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S. heteromorphus group compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 30-7-2021

Taxon Search:
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Short stable page link: https://mikrotax.org/Nannotax3/index.php?id=1214 Go to Archive.is to create a permanent copy of this page - citation notes



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