Original descriptions of taxa. For coccolithophores, and many calcispheres, these are pages from the 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 compiled by Prof A. Farinacci 1969-1989 and updated by Richard Howe 2000-2016 - see also this page.
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Hildebrand-Habel et al 1999 fig5.JPGCurrent identification/main database link:
Compiled data
Original Description
Diagnosis: Monocarinate cyst characterized by reticular surfaces. The single-layered wall consists of irregularly oriented, small, idiomorphous rhombohedrons. The central body of the holotype is basically spherical. The decisive feature is a circlet-like rim of coarser crystallites framing the apical side of the test.
Size: The diameter of the cyst (excluding ring) is 27 μm, the height (apical–antapical) 29 μm; the maximum width of the apical ring is 5 μm; the thickness of the wall in the reticular area is 1.7 μm; the pores show diameters of 1–1.6 μm; the archaeopyle is 8.5 μm in width.
Etymology: Latin, diadema, diadem, crown. Based on the circlet-like ring of coarser crystallites framing the apical side of the test.
Extra details from original publication
Description: The spherical central body of the cyst may be modified so that it has a conical hypocyst (Plate II, 14). A ring of coarse crystallites framing the apical side of the central body separates the slightly convex epicyst and convex to conical hypocyst (Fig. 5C; Plate II, 12). Further morphological features related to a paratabulation pattern are not noticeable. Hypocyst diameter may vary between 27 and 35 μm. The maximum diameter of the ring-like structure is 39 μm. The surface is characterized by a reticular pattern, formed of pores with diameters varying between 0.8 and 2 μm (Fig. 5B; Plate II, 15, 16). The single-layered wall consists of irregularly oblique oriented, small, idiomorphous rhombohedrons (Fig. 5B; Plate II, 13). All specimens additionally exhibit diagenetically altered, coarser crystallites. The walls in the reticular area are 1.6–3.3 μm thick. Broken specimens show a cavernous wall, due to the pores (Plate II, 16). Circular archaeopyles measuring 8.5– 12.8 μm are situated in the centre of the apical face of some specimens (Fig. 5A).
Relations: The net-like outer surface of this species seems to be similar to that of Sphaerodinella? albatrosiana (Kamptner, 1963) Keupp et Versteegh, 1989, and of the Operculodinella costata Group sensu Kienel, 1994, but Retesphaera diadema clearly differs in the irregular arrangement of small idiomorphous rhombohedrons in oblique orientation. Additionally, no other reticulate species is monocarinate and has an apical ring of crystallites. The cavernous constructed wall suggests affinities to Calcicarpinum tetramurus Kienel, 1994.
Stratigraphic range and regional distribution: Maastrichtian (NC21 and NC22) of the Sao Paulo Plateau, western South Atlantic Ocean, DSDP Leg 39, Site 356.
Hildebrand-Habel, T., Willems, H. & Versteegh, G. J. M. (1999). Variations in calcareous dinoflagellate associations from the Maastrichtian to Middle Eocene of the western South Atlantic Ocean (São Paulo Plateau, DSDP Leg 39, Site 356). Review of Palaeobotany and Palynology. 106: 57-87. gsReferences:
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Retesphaera diadema: Catalog entry compiled by Jeremy Young. Viewed: 1-10-2020
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