Kokia


Classification: Mesozoic -> Braarudosphaerales -> Other nannoliths with tangential c-axes -> Kokia
Sister taxa: Kokia, Tegulalithus,

Distinguishing features: Stellate, multiradiate, rosette-shaped nannoliths constructed from >6 single crystal-unit radial rays that show grey to white birefringence under XPL.


Daughter taxa: (blue => in age window 0-800Ma)
Stellate, multiradiate, rosette-shaped nannolith constructed from eight to ten single crystal-unit radial rays that show low birefringence under XPL. C-axes tangential.
Rosette-shaped nannolith with around eight rays with rounded terminations joined along curving sutures. Very short free ray length.

Stellate, multiradiate, rosette-shaped nannolith constructed from 10-15 single crystal-unit rays joined for most of their length along curved sutures; low birefringence under XPL.
Specimens not identified to species level

Taxonomy:

Citation: Kokia Perch-Nielsen, 1988
Rank: Genus
Type species: Kokia borealis Perch-Nielsen, 1988.

Farinacci & Howe catalog pages: Kokia *

Distinguishing features: Stellate, multiradiate, rosette-shaped nannoliths constructed from >6 single crystal-unit radial rays that show grey to white birefringence under XPL.


Evolution & Phylogeny: Varol & Girgis (1994) suggested Kokia might be ascidian spicules. However, the c-axis orientation appears wrong, in Ascidian spicules the c-axes are radial whilst they are tangential in Kokia or at least in the type species K. borealis. Alternative possibilities are that Kokia specimens are polycycloliths, or thin nannoconids.

Geological Range:
Last occurrence (top): in mid part of Valanginian Stage (54% up, 136.4Ma, in Valanginian stage). Data source: Total of range of species in this database
First occurrence (base): at base of Berriasian Stage (0% up, 145Ma, in Berriasian stage). Data source: Total of range of species in this database

Plot of occurrence data:

References:

Bown, P. R., Rutledge, D. C., Crux, J. A. & Gallagher, L. T. (1998). Early Cretaceous. In, Bown, P. R. (ed.) Calcareous Nannofossil Biostratigraphy. British Micropalaeontological Society Publication Series. 86-131. gs

Perch-Nielsen, K. (1988). New Lower Cretaceous calcareous nannofossil species from England. INA Newsletter. 10(1): 30-37. gs

Varol, O. & Girgis, M. (1994). New taxa and taxonomy of some Jurassic to Cretaceous calcareous nannofossils. Neues Jahrbuch für Geologie und Paläontologie Abhandlungen. 192: 221-253. gs


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Kokia compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 18-10-2019

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Short stable page link: http://mikrotax.org/Nannotax3/index.php?id=10542 Go to Archive.is to create a permanent copy of this page - citation notes



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