Daughter taxa (time control age-window is: 0-800Ma) | ||||
Alisphaera unicornis POL Distal cup entire, smooth | ||||
Alisphaera gaudii POL Distal cup with two lenticular openings | ||||
Canistrolithus valliformis POL Distal cup entire, with tubercles | ||||
Polycrater sp. with lip-like borders Distal cup entire, with wide smooth borders | ||||
Polycrater sp. minimum Distal cup entire, nannoliths very small (ca 0.2 µm) | ||||
Polycrater sp. with slit Distal cup with notch on one edge | ||||
Polycrater sp. ladle-like Distal cup incomplete, two petals normal, the other two reduced to a rod-like structure | ||||
Polycrater sp. two petals modified two absent Distal cup incomplete, two petals reduced to a rod-like structure, the other two absent | ||||
Polycrater sp. Specimens which cannot be assigned to established species |
Taxonomy:
By analogy with holococcoliths, where associations are demonstrated it will be appropriate to refer to these forms as polycrater (POL) phases of the respective heterococcolith species (e.g. Alisphaera gaudii POL). The only formally described species of Polycrater have now been shown to be parts of the life-cycle of Alisphaera species so the genus is now redundant.
Distinguishing features:
Parent taxon (Alisphaeraceae): Heterococcoliths asymetric, arranged in meridional rows on coccosphere; V-unit forms flange, R-unit basal. Also nannolith phase "Polycrater" with quadrate aragonitic liths.
This taxon: Phase with quadrate, cup-like nannoliths
Farinacci & Howe catalog pages: Polycrater *
Morphology:
Observations on collapsed coccospheres [JRY 2015 unpubl] suggest that the coccoliths are nealy dark in plan view and bright in side view suggesting they have their optic axes perpendicular to the the cell surface (NB Aragonite is similar optically to calcite - it has high birefirngence and negtive optical sign).
Biology & life-cycles
See also: Alisphaera ;Canistrolithus ;
Search data:LITHS: nannolith-radiate, quadrate, CA: ca_conjunct, CSPH: equant, monomorphic, CROSS-POLARS: V-prominent, |
Lith size: 0.3->1µm; Segments: 4->4; Coccosphere size: 5->16µm; |
Geological Range:
Last occurrence (top): Extant. Data source: Total of ranges of the species in this database
First occurrence (base): within No known fossil record modern (0.00-0.00Ma, base in "Holocene" stage). Data source: Total of ranges of species in this database
Plot of occurrence data:
Cros, L. & Fortuño, J. -M. (2002). Atlas of northwestern Mediterranean coccolithophores. Scientia Marina. 66: 1-186. gs Manton, I. & Oates, K. (1980). Polycrater galapagensis gen. et sp. nov., a putative coccolithophorid from the Galapagos Islands with an unusual aragonitic periplast. British Phycological Journal. 15: 95-103. gs Supraha, L., Ljubesic, Z. & Henderiks, J. (2018). Combination coccospheres from the Eastern Adriatic coast: New, verified and possible life-cycle associations. Marine Micropaleontology. 141: 23-30. gsReferences:
Polycrater phase compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 20-9-2024
Short stable page link: https://mikrotax.org/Nannotax3/index.php?id=1059 Go to Archive.is to create a permanent copy of this page - citation notes |
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