Nannotax3 - ntax_cenozoic - Alisphaeraceae

Citation: Alisphaeraceae Young et al., 2003

Type species: Alisphaera Heimdal 1973.

Taxonomic discussion: The genera Alisphaera, and Canistrolithus are combined in this family on the grounds of very similar, and distinctive coccolith structure. Polycrater is included following observation of combination coccospheres (Cros & Fortuño 2002, Supraha et al. 2018). This is an aragonitic nannolith (Manton & Oates 1980, Young et al. 1999) and strongly supports the family-level separation of this group.

Distinguishing features: Heterococcoliths asymetric, arranged in meridional rows on coccosphere; V-unit forms flange, R-unit basal. Also nannolith phase "Polycrater" with quadrate aragonitic liths.

Morphology:
Overview: The Alisphaeraceae are 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.
Alternate life-cycle phase typically: motile, bearing quadrate, aragonitic, nannoliths. Nannoliths with conical upper part and cruciform base.
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.

Biology & life-cycles: None of these species have been cultured yet. Observations of combination coccospheres of Alisphaera with Polycrater and of Canistrolithus with Polycrater suggest that these are alternate phases (Cros et al. 2000, Cros & Fortuño 2002, Supraha et al. 2018). By analogy with other taxa, we predict that the heterococcolith phase (Alisphaera/Canistrolithus) is diploid and that the nannolith phase (Polycrater) is haploid.

Geological Range:
Last occurrence (top): Extant Data source: Total of range of species in this database
First occurrence (base): at base of Gelasian Stage (0% up, 2.6Ma, in Gelasian stage). Data source: Total of range of species in this database

References:

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

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 V O

Heimdal, B. R. (1973). Two new taxa of Recent coccolithophorids. “Meteor” Forschungsergebnisse, Reihe D, Biologie. 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 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

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, Special Issue. 1: 1-132. gs V O

Daughter taxa (time control age-window is: 0-800Ma)		Granddaughter taxa
	Alisphaera Coccoliths placolith-like, with asymmetrical distal flange	A. capulata group A. extenta group A. unicornis group A. sp.
	Canistrolithus Coccoliths elongate oblong muroliths with asymmetric distal flange	C. valliformis C. sp.
	Polycrater phase Phase with quadrate, cup-like nannoliths	A. unicornis POL A. gaudii POL C. valliformis POL P. sp. with lip-like borders P. sp. minimum P. sp. with slit P. sp. ladle-like P. sp. two petals modified two absent P. sp.

Tags	LITHS:
Metrics	Lith size: 1->3.5µm;

Alisphaeraceae

References:

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