Daughter taxa (time control age-window is: 0-800Ma)![]() | ||||
![]() | ![]() | ![]() | ![]() | Sphenolithus arthurii Large, robust sphenolith with squat, square base and short, sharply tapering spine. |
![]() | ![]() | ![]() | ![]() | Sphenolithus orphanknollensis Small, with narrow, tapering spine. |
![]() | ![]() | ![]() | Sphenolithus pseudoradians Medium to large sphenolith with a tall compound spine. Distinguished from Sphenolithus radians by its larger size, more irregular outline and apical cycles that extend laterally beyond the base of the apical spine. | |
![]() | ![]() | ![]() | ![]() | Sphenolithus radians Medium to large sized (height 6.6-12.1 µm) with a tall compound spine and square shaped base with equidimensional quadrants. The spine is dark but visible at 0° and characterized by a median suture line; at 45° the spine is brightest. Narrow spine endings up to three times the length of the main sphenolith have been rarely observed (up to 38 µm). |
![]() | ![]() | ![]() | ![]() | Sphenolithus richteri Small narrow sphenolith with square base, comprising equidimensional quadrants, and tapering monocrystalline spine that is dark at 0° and bright at 45°. |
![]() | ![]() | ![]() | ![]() | Sphenolithus runus Spinose, dart-shaped sphenolith with a low base comprising a single cycle of triangular quadrants when viewed at 0°. The relatively tall, tapering spine is in extinction at 0° and bright at 45°. The quadrants appear larger, and are extended distally, at 45°. |
![]() | ![]() | ![]() | ![]() | Sphenolithus spiniger Small to medium sized (height 4.0-9.4 µm) with short spine, narrow triangular shape (dart shaped). Lower quadrants are largest and the compound spine is dark at 0°. |
Taxonomy:
Distinguishing features: Eocene to Early Oligocene sphenoliths with compound spines, that are visible but dim at 0° and brightest when at 45° to the polarizing directions.
Farinacci & Howe catalog pages:
Morphology: Sphenolith base typically has four distinct quadrants and is square or tapering. In older forms the spines are compound, becoming duo- or monocrystalline in later-appearing forms, and are usually visible but dim at 0° and brightest when at 45° to the polarizing directions; S. furcatolithoides spines behave slightly differently. Species are differentiated based on overall height and shape, spine size and degree of taper. Sphenolithus furcatolithoides, S. perpendicularis, S. kempii and S. cuniculus form a distinct subgroup with first three/four spines then two separate spines that bifurcate directly above the base. S. strigosus has a duocrystalline spine, a higher spine bifurcation point and is dark at 45°.
The group contains predominantly Eocene forms, namely: S. arthuri, S. conspicuus, S. editus, S. orphanknollensis, S. pseudoradians, S. radians, S. spiniger, S. villae; and in the S. furcatolithoides subgroup: S. cuniculus, S. furcatolithoides, S. perpendicularis, S. kempii, S. strigosus and, tentatively, S. runus.
Tags | LITHS: |
Metrics | Lith size: 3->11µm; |
Geological Range:
Last occurrence (top): in lower part of Chattian Stage (25% up, 26.8Ma, in Chattian stage). Data source: Total of range of species in this database
First occurrence (base): in lower part of Ypresian Stage (22% up, 54.2Ma, in Ypresian stage). Data source: Total of range of species in this database
Plot of occurrence data:
![]() |
S. radians 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=1217 Go to Archive.is to create a permanent copy of this page - citation notes |