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:
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
Tags | LITHS: |
Metrics | Lith size: 4->20µm; |
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:
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S. heteromorphus group compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 8-3-2021
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 |