Transitional genera

Classification: ntax_mesozoic -> Braarudosphaerales -> Transitional genera
Sister taxa: Braarudosphaeraceae, Transitional genera, Nannoconaceae ⟩⟨ Polycyclolithaceae, Other nannoliths with tangential c-axes

Distinguishing features: Nannoliths intermediate between Nannoconacaea and Braarudosphaeraceae

Daughter taxa (time control age-window is: 0-800Ma)Granddaughter taxa
Six-rayed, stellate to hexagonal nannoliths.

Globular and stellate nannoliths formed of 5-8 segments of stacked elements. Nannoconus-like in side view.  


Citation: Transitional genera
Rank: Family
Taxonomic discussion: The genera Polycostella and Hexalithus are both predomiantly Tithonian andappear to be transitional forms between small nannoconids and Braarudosphaeraceae. it is not clear which family they should be placed in, or whether the two genera are discrete. To highlight their postion and similarities they are grouped together here as "transitional genera".

Farinacci & Howe catalog pages: Transitional genera [no catalog entry yet]

Distinguishing features: Nannoliths intermediate between Nannoconacaea and Braarudosphaeraceae

Search data:
MetricsLith size: 0->0┬Ám;
The morphological data given here can be used on the advanced search page. See also these notes

Geological Range:
Last occurrence (top): within Berriasian Stage (139.39-145.01Ma, top in Berriasian stage). Data source:
First occurrence (base): within Tithonian Stage (145.01-152.06Ma, base in Tithonian stage). Data source:

Plot of occurrence data:



Transitional genera compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 15-6-2021

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

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