Nannotax3 - ntax_cenozoic - Polycrater phase

Polycrater phase


Classification: ntax_cenozoic -> Coccolith families inc sed -> Alisphaeraceae -> Polycrater phase
Sister taxa: Alisphaera, Canistrolithus, Polycrater phase

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:

Citation: Polycrater phase of Alisphaera or Canistrolithus
Rank: species group
Type species: Polycrater galapagensis Manton & Oates, 1980
Taxonomic discussion: Cros & Fortuño (2002) have shown that Polycrater forms combination coccospheres with Alisphaera and Canistrolithus. They also showed that a range of different morphotypes can be recognised, including forms with holes, skeletal forms, and forms with tubercles (“dots”). These morphotypes are mostly based on rather few specimens, so it is conceivable that they intergrade. However, since there are numerous Alisphaera spp., we suspect that most of them will prove to be discrete forms each forming part of the life-cycle of a different Alisphaera or Canistrolithus species.
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:

Coccoliths are aragonitic; quadrate in plan view, hour-glass shaped in profile; ca. 1 µm across; formed of upper cone and a cross-shaped base of four feet. Very numerous coccoliths on each coccosphere, spirally arranged.
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).

Size:


Biology & life-cycles: Combination coccospheres with Alisphaera and Canistrolithus species have been observed (Cros & Fortuño 2002, Supraha et al. 2018).

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;
The morphological data given here can be used on the advanced search page. See also these notes

Geological Range:
Last occurrence (top): Extant. Data source: Total of range of species in this database
First occurrence (base): at top of No known fossil record modern (100% up, 0Ma, in "Holocene" stage). Data source: Total of range of species in this database

Plot of occurrence data:

References:

Cros, L. & Fortuño, J. -M. (2002). Atlas of northwestern Mediterranean coccolithophores. Scientia Marina. 66: 1-186. gs V O

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 V O

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. gs


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Polycrater phase compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 27-9-2022

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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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