Retecapsa


Classification: Mesozoic -> Podorhabdales -> Cretarhabdaceae -> Retecapsa
Sister taxa: Cretarhabdus, Cruciellipsis, Flabellites, Grantarhabdus, Helenea, Mattiolia, Miravetesina, Pickelhaube, Retecapsa, Speetonia,

Distinguishing features: Cretarhabdids with a relatively wide central area spanned by an axial cross with lateral bars.


Daughter taxa: (blue => in age window 0-300Ma)

Small to medium-sized cretarhabdids with distal shields that slope in to the central-area, which is spanned by an axial cross with numerous lateral bars (7-8 in each quadrant). Distal shield does not appear to be bicyclic.
Retecapsa with a three lateral bars in each quadrant (delimiting around 16 perforations).
Retecapsa with about two lateral bars in each quadrant (delimiting around 12 perforations).
Retecapsa with a relatively wide central area (>1/3 the minimum diameter of the distal shield) spanned by an axial cross with one centrally-placed broad lateral bar in each quadrant. A particularly diagnostic feature is that all the central area bars are equally broad and birefringent. The 8 central area holes are of relatively equal size.
Retecapsa with relatively broad shield and narrow central area spanned by an axial cross with one centrally-placed narrow lateral bar in each quadrant. The 8 central area holes are of relatively equal size.
Retecapsa with relatively broad central area spanned by an axial cross with one narrow lateral bar in each quadrant located towards the end of the central area. The 8 central area holes are of unequal size.
Small to medium sized retecapsids with axial cross bars that are broad and bright in XPL with median extinction lines. Distinctly bicyclic rim image in XPL.
Small Retecapsa with narrow central area entirely closed by bars
Specimens not identified to species level

Taxonomy:

Citation: Retecapsa Black, 1971
Rank: Genus
Type species: Retecapsa brightonii Black, 1971 (considered a synonym of R. angustiforata
Synonyms: Heterorhabdus Noël 1970 - type species H. sinuosus Noël 1970 which is considered a synonym of R. crenulata. This appears to be a senior synonym of Retecapsa.
Notes & discussion: Closely related to Cretarhabdus, they are separated on the rather subjective criteria of a single cycle of bars being present in Retecapsa vs. a net in Cretarhabdus.
Some authors have included these forms within Cretarhabdus. and this might be preferable given that Heterorhabdus is probably a senior synonym of Retecapsa.

Farinacci & Howe catalog pages: Heterorhabdus * Retecapsa + *

Distinguishing features: Cretarhabdids with a relatively wide central area spanned by an axial cross with lateral bars.

Geological Range:
Last occurrence (top): within Maastrichtian Stage (66.04-72.05Ma, top in Maastrichtian stage). Data source: Total of range of species in this database
First occurrence (base): within Toarcian Stage (174.15-182.70Ma, base in Toarcian stage). Data source: Total of range of species in this database

Plot of occurrence data:

References:

Black, M., (1971). Coccoliths of the Speeton Clay and Sutterby Marl. Proceedings of the Yorkshire Geological Society, 38: 381-424.

Bown, P.R. & Cooper, M.K.E., (1998). Jurassic. In: Bown, P.R. (Editor), Calcareous nannofossil biostratigraphy. British Micropalaeontological Society Publication Series. Chapman & Hall, pp. 34-85.

Burnett, J.A., (1998). Upper Cretaceous. In: Bown, P.R. (Editor), Calcareous Nannofossil Biostratigraphy. British Micropalaeontological Society Publications Series. Chapman & Hall, London, pp. 132-199.

Noël, D., (1970). Coccolithes Crétacés: La Craie Campanienne du Bassin de Paris. Éditions du Centre National de la Recherche Scientifique, Paris.


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Retecapsa compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 20-7-2018

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