Classification: Coccolithophores -> Discoasterales -> Heliolithaceae -> Bomolithus
Sister taxa: Bomolithus, Heliolithus

Daughter taxa: (blue => in age window 0-800Ma)
Bomolithus aquilus
Medium-sized, circular heliolith with at least two discernible cycles in LM, both of which are dark in XPL. The cycles comprise around 40 visible radial elements and the central area is typically closed.
Bomolithus bramlettei
Similar to B. megastypus but fewer rays and inner cycle less elevated
Bomolithus conicus

Bomolithus elegans
Medium to large rosette-shaped discoasteralid with prominent, broad birefringent cycle (greater than half the lith diameter).
Bomolithus megastypus
Medium to large rosette-shaped discoasteralid with prominent, narrow birefringent boss (equal to or less than half the lith diameter).
Bomolithus supremus
Circular lith with three distinct cycles, only the innermost exhibiting birefringence in XPL; the central area is a narrow hole or closed. The outermost cycle is dark in phase contrast and the distinct elements show obliquity. The innermost cycle shows white interference colours and is crossed by thick extinction lines that are rotated approximately 5° from axial.
Bomolithus sp.
Specimens which cannot be assigned to any established species


Citation: Bomolithus Roth, 1973
Rank: Genus
Type species: Bomolithus elegans Roth, 1973.
Taxonomic discussion: The genus Discoasteroides Bramlette & Sulivan 1961 was used at one time for many of these speceis. However, the type species D. kuepperi is a regular discoaster. See also discussion in Young & Bown 2014 (p.42).

Distinguishing features: Discoidal discoasteralids with a wide non-birefringent cycle and at least one narrower birefringent cycle, i.e., narrower than the diameter of the nannolith.

Farinacci & Howe catalog pages: Bomolithus *

Search data:
TagsLITHS: nannolith-radiate, circular, star-shaped, CROSS-POLARS: V-prominent, R-prominent,
MetricsLith size: 5->12µm;
The morphological data given here can be used on the advanced search page. See also these notes

Geological Range:
Last occurrence (top): at base of Ypresian Stage (1% up, 55.9Ma, in Ypresian stage). Data source: Total of range of species in this database
First occurrence (base): at base of Selandian Stage (4% up, 61.5Ma, in Selandian stage). Data source: Total of range of species in this database

Plot of occurrence data:


Bown, P. R. (2010). Calcareous nannofossils from the Paleocene/Eocene Thermal Maximum interval of southern Tanzania (TDP Site 14). Journal of Nannoplankton Research. 31(1): 11-38. gs V O

Roth, P. H. (1973). Calcareous nannofossils: Leg 17 of the Deep Sea Drilling Project. Initial Reports of the Deep Sea Drilling Project. 17: 695-795. gs V O

Young, J. R. & Bown, P. R. (2014). Some emendments to calcareous nannoplankton taxonomy. Journal of Nannoplankton Research. 33(1): 39-46. gs V O


Bomolithus compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 29-11-2020

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Short stable page link: Go to to create a permanent copy of this page - citation notes

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