Taxonomy:
Distinguishing features:
Parent taxon (Rhabdosphaeraceae): BCs planoliths with radial lath cycle and highly-variable axial structures. Often polymorphic and/or varimorphic
This taxon: Coccoliths process-bearing with complex base including outer rim, radial lath and lamellar cycles
Original description: Coccoliths belonging to this genus are characterized by a single circular shield with a perforate ring spanned by interlocking ribs near the periphery.
Farinacci & Howe catalog pages: Blackites + * , Amitha * , Cruxia * , Naninfula + * , Cepekiella * , Discoturbella * , Notiocyrtolithus * , Ommatolithus * , Pseudotriquetrorhabdulus * , Wiseorhabdus *
Morphology:
1) a bicyclic outer rim (as in other Rhabdosphaeraceae);
2) a radial lath cycle (often with two laths per rim unit);
3) multiple lamellar cycles with clockwise obliquity.
These three cycles are consistently present, the processes however have highly variable structure, including forms with multiple tiers of additional cycles.
Size:
LITHS: planolith, elliptical, CA: ca_disjunct, grill, process, |
Lith size: 4->30µm; |
Geological Range:
Last occurrence (top): at top of Oligocene Epoch (100% up, 23Ma, in Aquitanian stage). Data source: Total of ranges of the species in this database
First occurrence (base): within NP9 zone (55.86-57.21Ma, base in Thanetian stage). Data source: Total of ranges of species in this database
Plot of occurrence data:
Aubry, M. -P. (1999). Handbook of Cenozoic calcareous nannoplankton. Book 5: Heliolithae (Zygoliths and Rhabdoliths). Micropaleontology Press, American Museum of Natural History, New York. 1-368. gs Bown, P. R. & Newsam, C. (2017). Calcareous nannofossils from the Eocene North Atlantic Ocean (IODP Expedition 342 Sites U1403–1411). Journal of Nannoplankton Research. 37(1): 25-60. gs O 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 O Hay, W. W. & Towe, K. M. (1962a). Electron microscope examination of some coccoliths from Donzacq (France). Eclogae Geologicae Helvetiae. 55: 497-517. gs O Shafik, S. (1989). Some new calcareous nannofossils from Upper Eocene and Lower Oligocene sediments in the Otway Basin, southeastern Australia. Alcheringa. 13: 69-83. gs Varol, O. (1989b). Eocene calcareous nannofossils from Sile (northwest Turkey). Revista Española de Micropaleontología. 21: 273-320. gs References:
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Blackites compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 7-2-2025
Short stable page link: https://mikrotax.org/Nannotax3/index.php?id=86 Go to Archive.is to create a permanent copy of this page - citation notes |
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