Cretarhabdus conicus Bramlette & Martini, 1964
Stradneria Reinhardt, 1964
Cretarhabdella Black, 1971a
The placolith comprises a cretarhabdid pelaga sloping towards the central area, formed of inclined segments that are typically weakly clockwise-imbricated, though rarely non-imbricate, and a distally arched central area characterised by a fibrous axial cross supporting a solid distal process.
The inter-cross area is occupied by lateral bars that delimit pores arranged in two or more complete concentric cycles, a feature characteristic of Cretarhabdus.
The number of pores in the outer cycle is used to distinguish species of Cretarhabdus, except for Cretarhabdus conicus, which is characterised by the overlapping of the arm tips of the axial cross onto the pelaga.
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.
Black, M. 1971a. Coccoliths of the Speeton Clay and Sutterby Marl. Proceedings of the Yorkshire Geological Society 38: 381-424.
Bramlette, M. N. & Martini, E. 1964. The great change in calcareous nannoplankton fossils between the Maastrichtian and Danian. Micropaleontology. 10(2): 291-322.
Grün, W. & Allemann, F. 1975. The Lower Cretaceous of Caravaca (Spain): Berriasian Calcareous Nannoplankton of the Miravetes Section (Subbetic Zone, Prov. of Murcia). Eclogae Geologicae Helvetiae, 68: 147-211.
Noël, D. 1965. Sur les Coccolithes du Jurassique Européen et d'Afrique du Nord. Essai de classification des coccolithes fossiles. Éditions du Centre National de la Recherche Scientifique, Paris. 1-129.
Reinhardt, P. 1964. Einige Kalkflagellaten-Gattungen (Coccolithophoriden, Coccolithineen) aus dem Mesozoikum Deutschlands. - Monatsberichteder Deutschen Akademieder Wissenschaftenzu Berlin. 6: 749-759.