Nannotax3 - ntax_mesozoic - Bifidalithus mchanae <title>Nannotax3 - ntax_mesozoic - Bifidalithus mchanae

Bifidalithus mchanae

Classification: ntax_mesozoic -> Holococcoliths -> Rarer genera -> Bifidalithus -> Bifidalithus mchanae
Sister taxa: B. geminicatillus, B. mchanae, B. sp.

Distinguishing features:
Parent taxon (Bifidalithus): Holococcoliths formed from two blocks divided by a transverse suture.
This taxon: Pore on each block, no rim


Citation: Bifidalithus mchanae Lees, 2007
Rank: Species

Farinacci & Howe catalog pages: B. mchanae * , P. evanescens *

Distinguishing features:
Parent taxon (Bifidalithus): Holococcoliths formed from two blocks divided by a transverse suture.
This taxon: Pore on each block, no rim


"A small species of Bifidalithus Varol, 1991 in which the two main constituent elements contain a single perforation each, arranged around the short-axis junction between the elements. The junction between these elements appears raised. Differentiation: This species is distinct from B. geminicatillus in possessing perforations. In side view (Pl.10, figs 70, 71), the raised area where the elements join appears to arch over a cavity above a monoperforate proximal plate." [Lees 2007]

"Elliptical coccolith composed of two, nearly symmetrical calcite blocks separated by a distinct, sinuous suture. Each block contains a small, central circular opening (~1 µm in width). There is no central spine. These two blocks exhibit different optical properties in cross-polarized light. When the major axis is oriented north to south, one calcite block appears dull or extinct, while the second exhibits pronounced birefringence." [Blair & Watkins 2009]

Holotype dimensions: L = 4.62μm, W = 3.08μm.

Ecology & Biogeography

Biology & life-cycles

Phylogenetic relations

Search data:
LITHS: holococcolith, elliptical, CA: ca_disjunct, pores, CROSS-POLARS: rim-unicyclic, V-prominent,
Lith size: 4->6µm; Segments: 2->2;
Data source notes: holotype +/-1µm
The morphological data given here can be used on the advanced search page. See also these notes

Geological Range:
Last occurrence (top): within Early Maastrichtian Substage (69.91-72.05Ma, top in Maastrichtian stage). Data source: Lees 2007 (original description)
First occurrence (base): within Early Santonian Substage (85.56-86.26Ma, base in Santonian stage). Data source: Blair & Watkins 2009

Plot of occurrence data:


Blair, S. A. & Watkins, D. K. (2009). High-resolution calcareous nannofossil biostratigraphy for the Coniacian/Santonian Stage boundary, Western Interior Basin. Cretaceous Research. 30(2): 367-384. gs

Lees, J. A. (2007). New and rarely reported calcareous nannofossils from the Late Cretaceous of coastal Tanzania: outcrop samples and Tanzania Drilling Project Sites 5, 9 and 15. Journal of Nannoplankton Research. 29(1): 39-65. gs O


Bifidalithus mchanae compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 30-1-2023

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