Nannotax3 - ntax_cenozoic - S. heteromorphus group

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:

Tags	LITHS:
Metrics	Lith 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:

Range-bar - range as quoted above, pink interval top occurs in, green interval base occurs in.
Triangles indicate an event for which a precise placement has been suggested
Neptune data: this is a higher taxon page so Neptune data is not plotted. For the customisable plot option go to a genus page Parent: Sphenolithus

References:

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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