Distinguishing features:
Parent taxon (Rarer genera): Less common genera
This taxon: Elliptical, cavate (and usually septate) holococcoliths, often bearing hollow spines. Distal surfaces may be perforate and there may be internal buttresses.
Daughter taxa (time control age-window is: 0-800Ma) | ||||
Anfractus harrisonii Small, spinous holococcolith with diagonal internal structures that are bright and diagnostic in XPL. Distal surface with perforations. | ||||
Anfractus parvus Small Anfractus species with a sharply tapering spine and low rim | ||||
Anfractus variabilis Very small holococcolith with distal surface pierced by 8-10 pores. | ||||
Anfractus youngii Holococcolith with broad, tall, tapering spine and diagonal internal septa. | ||||
Anfractus sp. Specimens not identified to species level |
Taxonomy:
Farinacci & Howe catalog pages: Anfractus + *
Distinguishing features:
Parent taxon (Rarer genera): Less common genera
This taxon: Elliptical, cavate (and usually septate) holococcoliths, often bearing hollow spines. Distal surfaces may be perforate and there may be internal buttresses.
Search data:
LITHS: holococcolith, elliptical, hollow, CA: diagonal cross, process, ca_disjunct, CROSS-POLARS: R-prominent, rim-unicyclic, |
Lith size: 1->5µm; Data source notes: size range of included species |
Geological Range:
Last occurrence (top): at top of NJ16a subzone (100% up, 149.1Ma, in Tithonian stage). Data source: Total of ranges of the species in this database
First occurrence (base): within Toarcian Stage (174.70-184.20Ma, base in Toarcian stage). Data source: Total of ranges of species in this database
Plot of occurrence data:
Bown, P. R. & Cooper, M. K. E. (1998). Jurassic. In, Bown, P. R. (ed.) Calcareous Nannofossil Biostratigraphy. British Micropalaeontological Society Publication Series . 34-85. gs O Medd, A. W. (1979). The Upper Jurassic coccoliths from the Haddenham and Gamlingay boreholes (Cambridgeshire, England). Eclogae Geologicae Helvetiae. 72: 19-109. gs OReferences:
Anfractus compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 10-12-2024
Short stable page link: https://mikrotax.org/Nannotax3/index.php?id=10017 Go to Archive.is to create a permanent copy of this page - citation notes |
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