Retecapsa brightonii Black, 1971a
Heterorhabdus Noël, 1970 is a later homonym of Heterorhabdus Giesbrecht, 1892 (Copepoda) and is therefore illegitimate under ICN Art. 53. It was replaced by Retecapsa Black, 1971a.
The placolith comprises a cretarhabdid pelaga sloping towards the central area, formed of inclined segments that are commonly weakly clockwise-imbricated, and only rarely non-imbricate, and a distally arched central area characterised by an axial cross supporting a solid distal process.
The inter-cross area is occupied by lateral bars that delimit pores arranged in a single complete concentric cycle, a feature characteristic of Retecapsa.
The number of pores is used to distinguish species of Retecapsa.
The placolith generally displays first-order, greyish-white interference colours; however, it becomes dimmer towards the periphery, where only the inner layer of the distal shield is developed. In plan view under crossed polars, the outer layer of the distal shield exhibits inclined extinction and length-fast (–) elongation.
In this study, Retecapsa crenulata is not utilised, despite its frequent use in the literature, owing to its highly variable species concept. The holotype is preserved in side view, and the paratype, although in plan view, fails to clearly reveal the central structure.
Black, M. 1971a. Coccoliths of the Speeton Clay and Sutterby Marl. Proceedings of the Yorkshire Geological Society 38: 381-424.
Giesbrecht, W. 1892-1893. Systematik und Faunistik der pelagischen Copepoden des Golfes von Neapel und der angrenzenden Meeres-Abschnitte. Systematics and faunistics of the pelagic copepods of the Gulf of Naples and the adjacent marine areas. Fauna und Flora des Golfes von Neapel und der Angrenzenden Meeres-Abschnitte, Herausgegeben von der Zoologischen Station zu Neapel. 19:1-831, pls. 1-54 (published in sections over 2 years, 1892-1893).
Noël, D. 1970. Coccolithes Crétacés: La Craie Campanienne du Bassin de Paris. - Éditions du Centre National de la Recherche Scientifique, Paris. 1-129