Nannotax3 - ntax_Farinacci - Gephyrocapsaceae

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: Gephyrocapsaceae Black, 1971

Type species: Gephyrocapsa Kamptner

Current citation: Noelaerhabdaceae Jerkovic, 1970 emend. Young & Bown, 1997

Coccolithophorales bearing placoliths with a large central opening and with the shields constructed of non-imbricate radial elements.

(Gephyrocapsaceae: Coccolithophorales placolithos ellipticos ferentes; in medio coccolitho foramen amplum; pali geminorum scutorum commissuris orthogoniis. Genus typicum: Gephyrocapsa Kamptner.)

In the living genus Gephyrocapsa the rays of the distal shield do not overlap each other as they do in the genera so far considered, but lie side by side, with the sutures between adjacent rays nearly at right angles to the surface of the shield. The same arrangement is seen in Coccolithus huxleyi and in the species-group of C. doronicoides in the late Tertiary and Quaternary. Ellipsoplacolithus exsectus Kamptner and E. lacunosus Kamptner from Pleistocene cores in the Pacific are again very similar in the structure of their shields (Kamptner 1963, figs. 50-2); indeed, almost identical forms in Pleistocene cores from the North Atlantic have recently been figured under the name of Coccolithus doronicoides (Mclntyre and Be 1967, pl. 2B and pi. 3A).

In the Pleistocene, Mclntyre (1967) has found coccoliths intermediate in form between Gephyrocapsa oceanica and C. huxleyi, and he has given reasons for believing that C. huxleyi has evolved from the Gephyrocapsa stock. Recent work suggests that all these forms are closely related, and that they belong to a family that was actively evolving during the Pleistocene, independently of the Coccolithophoraceae. The name Gephyrocapsaceae is proposed for this family, with the following diagnosis: Coccolithophorales bearing placoliths with a large central opening and with the shields constructed of non-imbricate radial elements. Typical genus Gephyrocapsa Kamptner. (Gephyrocapsaceae: Coccolithophorales placolithos ellipticos ferentes; in medio coccolitho foramen amplum; pali geminorum scutorum commissuris orthogoniis. Genus typicum: Gephyrocapsa Kamptner.)

Coccoliths with a similar structure are abundant in the Tertiary; C. marismontium in the Middle Eocene has much in common with some variants of C. doronicoides, and there are forms in the Miocene and Pliocene which appear to link the two together. An independent generic name is needed for the C. doronicoides and C. marismontium complex of species, in which the placoliths have a large open centre and in which both shields consist of numerous non-imbricate rays. The earliest generic name other than Coccolithus which has been proposed for a coccolith of this kind appears to be Ellipsoplacolithus Kamptner. Loeblich and Tappan (1966, p. 139), invoking Article 34 of the International Code of Botanical Nomenclature, have regarded this name as not having been validly published. Nevertheless, when Kamptner (1963, p. 171) proposed Ellipsoplacolithus as a new genus, he gave a diagnosis in which it is treated as an organ-genus, and designated E. lacunosus Kamptner as type species. The name is thus provisional only in the same sense that all organ-genera are provisional, but not within the meaning of Article 34. If we therefore accept it as a legitimate name, Coccolithus doronicoides becomes Ellipsoplacolithus doronicoides (Black and Barnes) n. comb., and C. marismontium becomes E. marismontium (Black) n. comb.

The central opening of Gephyrocapsa is spanned distally by an oblique bridge, and proximally by a grille. A similar grille, but without a bridge, is present in C. huxleyi and in a large number of Tertiary species of Tremalithus as defined by the genotype, T. placomorphus. Reticulofenestra Hay, Mohler and Wade, and Dictyococcites Black differ very little from Tremalithus Kamptner, and probably ought to be merged into this genus.

All the forms discussed above fall quite naturally into the Gephyrocapsaceae. In the Cretaceous, there is an interesting complex of species whose relationships are not so clear-cut. They reach their greatest diversity in the Albian and Cenomanian, where there are forms with a bewildering combination of characters, some suggestive of the Gephyrocapsaceae, others of the Ellipsagelosphaeraceae. Much work will be needed before these can be satisfactorily sorted out; it may well be that we have here a record of an evolutionary divergence amongst whose products were the ancestors of the gephyrocapsoid stock that did not become clearly differentiated until the Tertiary.

Gephyrocapsaceae Hay 1977 is a junior homonym

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

Hay, W. W. (1977). Calcareous nannofossils. In, Ramsay, A. T. S. (ed.) Oceanic Micropalaentology. Academic Press, London (2): 1055-1200. gs

CATALOG - Gephyrocapsaceae

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