Daughter taxa (time control age-window is: 0-800Ma) | Granddaughter taxa | ||||
Alisphaera Coccoliths placolith-like, with asymmetrical distal flange | Alisphaera capulata Alisphaera memoria Alisphaera ordinata Alisphaera quadrilatera Alisphaera extenta Alisphaera gaudii Alisphaera unicornis Alisphaera spatula Alisphaera bidentata Alisphaera pinnigera Alisphaera sp. | ||||
Canistrolithus Coccoliths elongate oblong muroliths with asymmetric distal flange | |||||
Polycrater phase Phase with quadrate, cup-like nannoliths | Alisphaera unicornis POL Alisphaera gaudii POL Canistrolithus valliformis POL Polycrater sp. with lip-like borders Polycrater sp. minimum Polycrater sp. with slit Polycrater sp. ladle-like Polycrater sp. two petals modified two absent Polycrater sp. |
Taxonomy:
Distinguishing features:
Parent taxon (Coccolith families inc sed): 2N: Various heterococcolith groups not obviously related to the well-defined orders
N: mostly unknown
This taxon: Heterococcoliths asymetric, arranged in meridional rows on coccosphere; V-unit forms flange, R-unit basal. Also nannolith phase "Polycrater" with quadrate aragonitic liths.
Original description: Diagnosis: Cellulae coccolithiferae, status dominans cycli vitae erraticus, ferunt heterococcolithos dispositos secus series meridionales. Coccolithi irregulares cum margine directo versus polum flagellorum extenso in fimbriam vel extensionem. Coccolithus integer factus est ab monadibus labri; locus annuli proto-coccolithi intra tubum. V-elementi facunt tubum superum et fimbriam distalem; R-elementi facunt tubum bistratum inferum et constructiones proximales, aliquando cum extensione distali. Status alternatus cycli vitae erraticus, ferens nannolithos quadriangulatos aragoniticos. Nannolithi cum parte supero conico et base cruciforme.
Translation: Coccolithophores, dominant stage of life cycle typically: motile, bearing heterococcoliths arranged in meridional rows. Coccoliths asymmetrical with edge directed toward flagellar opening extended into a flange or protrusion. Entire coccolith formed of rim units; proto-coccolith ring locus within tube; V-units form upper tube and distal flange; R-units form two-layered lower tube and proximal structures, sometimes with distal extension.
Alternate life-cycle phase typically: motile, bearing quadrate, aragonitic, nannoliths. Nannoliths with conical upper part and cruciform base.
Farinacci & Howe catalog pages: Alisphaeraceae *
Morphology:
Overview: The Alisphaeraceae is a diverse family of extant coccolithophores, of rather low abundance and producing very small coccoliths. Their fossil record is virtually undocumented, but occasional specimens can be found in well-preserved sediments. As explained below, the coccolith structure does not fit easily in any of the main coccolith groups, and the alternate life-cycle phase produces quadrate aragonitic cup-shaped nannoliths instead of holococcoliths.
Heterococcolith stage: motile, coccosphere with liths regularly arranged in meridional rows. Coccoliths asymmetrical with edge directed toward flagellar opening extended into a flange or protrusion. Since the heterococcoliths have regular V/R structure it is reasonable to assume this is the diploid phase.
Alternate life-cycle phase: typically motile, bearing quadrate, aragonitic, nannoliths. Nannoliths with conical upper part and cruciform base. Formerly regarded the separate genus Polycrater. This is presumably the hsploid phase.
Heterococcolith structure: As discussed by Kleijne et al. (2002), the proto-coccolith ring is located approximately halfway up the tube. Our LM observations indicate that the upper unit (D-unit of Kleijne et al. 2002) is the V-unit, this forms the distal flange and upper tube. The R-unit forms the inner and outer layers of the lower tube (with slightly different imbrication directions), and in Alisphaera the proximal flange and central area grill. [Young et al. 2003]
NB The colour images of Alisphaera coccospheres in xpl with the gypsum plate show unambiguously that the distal shield is formed of V-unis and the proximal shield of R-units [my interpretation - JRY 2023]
Size:
Biology & life-cycles
Lith size: 1->3.5µm; |
Geological Range:
Last occurrence (top): Extant. Data source: Total of ranges of the species in this database
First occurrence (base): within Quaternary Period (0.00-2.59Ma, base in Gelasian 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 Cros, L., Kleijne, A. & Young, J. R. (2000a). Coccolithophorid diversity in the genus Polycrater and possible relationships with other genera. Journal of Nannoplankton Research. 22(2): 92-92. gs Heimdal, B. R. (1973). Two new taxa of Recent coccolithophorids. “Meteor” Forschungsergebnisse. (13): 70-75. gs Kleijne, A., Jordan, R. W., Heimdal, B. R., Samtleben, C., Chamberlain, A. H. L. & Cros, L. (2002). Five new species of the coccolithophorid genus Alisphaera (Haptophyta) with notes on their distribution, coccolith structure and taxonomy. Phycologia. 40(6): 583-601. 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. gs Young, J. R., Davis, S. A., Bown, P. R. & Mann, S. (1999). Coccolith ultrastructure and biomineralisation. Journal of Structural Biology. 126: 195-215. gs Young, J. R., Geisen, M., Cros, L., Kleijne, A., Probert, I. & Ostergaard, J. B. (2003). A guide to extant coccolithophore taxonomy. Journal of Nannoplankton Research. S1: 1-132. gs References:
Alisphaeraceae 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=36 Go to Archive.is to create a permanent copy of this page - citation notes |
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