Anfractus


Classification: Mesozoic -> Holococcoliths -> Rarer genera -> Anfractus
Sister taxa: Bifidalithus, Bilapillus, Multipartis, Munarinus, Octolithus, Okkolithus, Ottavianus, Pharus, Ramsaya, Russellia, Saepiovirgata, Acuturris, Anfractus, Duocameratus, Lacunolithus-Bown, Metadoga, Nicholasia, Paulpearsonia, Petrobrasiella, Pseudoconus, Semihololithus, Stereorhabdus, Tanzanella, Thecatus, unidentified holococcoliths,

Distinguishing features: Elliptical, cavate (and usually septate) holococcoliths, often bearing hollow spines. Distal surfaces may be perforate and there may be internal buttresses.


Daughter taxa: (blue => in age window 0-800Ma)
Small, spinous holococcolith with diagonal internal structures that are bright and diagnostic in XPL. Distal surface with perforations.
Small Anfractus species with a sharply tapering spine and low rim
Very small holococcolith with distal surface pierced by 8-10 pores.
Holococcolith with broad, tall, tapering spine and diagonal internal septa.
Specimens not identified to species level

Taxonomy:

Citation: Anfractus Medd, 1979
Rank: Genus
Type species: Anfractus harrisonii Medd, 1979

Farinacci & Howe catalog pages: Anfractus + *

Distinguishing features: Elliptical, cavate (and usually septate) holococcoliths, often bearing hollow spines. Distal surfaces may be perforate and there may be internal buttresses.

Geological Range:
Last occurrence (top): at base of Tithonian Stage (2% up, 151.9Ma, in Tithonian stage). Data source: Total of range of species in this database
First occurrence (base): at base of Toarcian Stage (0% up, 182.7Ma, in Toarcian stage). Data source: Total of range of species in this database

Plot of occurrence data:

References:

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

Medd, A. W. (1979). The Upper Jurassic coccoliths from the Haddenham and Gamlingay boreholes (Cambridgeshire, England). Eclogae Geologicae Helvetiae. 72: 19-109. gs


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Anfractus compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 18-9-2019

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Short stable page link: http://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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