Nannotax3 - ntax_Farinacci - Helicosphaeraceae

Original descriptions of taxa. For coccolithophores, and many calcispheres, these are pages from the Farinacci & Howe Catalog of Calcareous Nannofossils. In other cases (e.g. non-calcifying haptophytes) the data is directly compiled on this site. The "Catalogue of Calcareous Nannofossils" was originally compiled by Prof A. Farinacci 1969-1989, since 2000 it has been updated and extended by Richard Howe - see The Farinacci and Howe Catalog - an Introduction.
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Citation: Helicosphaeraceae Black, 1971

Type species: Helicosphaera Kamptner

Current citation: Helicosphaeraceae Black, 1971

Diagnosis: Coccolithophorales whose coccoliths have a large elliptical central shield surrounded by a spiral or otherwise asymmeuical flange constructed of radial elements.

Coccolithophorales coccolithis irregulariter ellipticis; in medio coccolitho scutum magnum ellipticum, ora inaequali circumdatum; ora palls angustis structa, vel in cochleam serpens, vel aliter inaequalis.

The peculiar coccoliths for which Kamptner created the genus Helicosphaera were for many years regarded as asymmetrically developed placoliths, and many authors have included them in Coccosphaera or Coccolithophora. The internal structure of the massive central area is still not fully understood, but is clearly quite different from the pillar or tube of a placolith, and the petaloid elements are arranged in a single spiral band and not in two separate annular shields.

Looking back into the Tertiary, we find a succession of species that share these peculiarities, and the genus Helicosphaera can confidently be traced back to the Eocene. The early species are associated with other asymmetrical coccoliths included in the genus Lophodolithus; in these the petaloid flange is apparently not spiral, but is more strongly developed at one sector of the periphery than elsewhere. Lophodolithus is unknown from pre-Tertiary rocks, but Kamptnerius in the Upper Cretaceous shares some of its peculiarities.

With the information available at present, it is difficult to assess the phylogenetic significance of an asymmetrical flange. Bramlette and Sullivan (1961) have given evidence of a gradation between the two genera in the less extreme forms of Lophodolithus and Zygodiscus, but there is as yet no connecting link between either of these and Kamptnerius. At no time in the known geological history of these genera is there any sign of derivation from a placolith-like structure.

References:

Black, M. (1971c). The systematics of coccoliths in relation to the paleontological record. In, Funnell, B. M. & Riedel, W. R. (eds) The Micropaleontology of the Oceans. Cambridge University Press, Cambridge 611-624. gs O

CATALOG - Helicosphaeraceae

References:

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