Nannotax3 - ntax_mesozoic

Nannotax3 - ntax_mesozoic - Retecapsa Nannotax3 - ntax_mesozoic - Retecapsa

Retecapsa

Classification: ntax_mesozoic -> Podorhabdales -> Cretarhabdaceae -> Retecapsa
Sister taxa: Mattiolia, Wisea ⟩⟨ Speetonia ⟩⟨ Cruciellipsis, Flabellites, Grantarhabdus, Helenea ⟩⟨ Cretarhabdus, Retecapsa, Pickelhaube, Miravetesina

Distinguishing features:
Parent taxon (Cretarhabdaceae): Regular placoliths; central-area spanned by elevated distal structure typically with cross bars and central spine.
The distal shield usuallyappers to be weakly bicyclic in the SEM, with a narrow outer-cycle and broad inner-cycle; elements usually radial and non-imbricate. LM image is moderately birefringent. V/R structure unclear.
This taxon: Cretarhabdids with central area spanned by an axial cross with lateral bars.

All these species are medium sized (5-8 µm) unless noted otherwise. (time control age-window is: 0-800Ma)
				Axial cross only
				Retecapsa incompta Cretarhabdids with axial cross bars that are broad and bright in XPL with median extinction lines. Distinctly bicyclic rim image in XPL.
				Axial cross & 1 lateral bar per quadrant
				Retecapsa angustiforata Cretarhabdids with axial cross & 1 lateral bar per quadrant; central area relatively wide (>1/3 the shield width). All bars of similar breadth and brightness and all 8 holes of similar size.
				Retecapsa beckii Small (4-5 µm) cretarhabdids with 1 lateral bar per quadrant
				Retecapsa octofenestrata Cretarhabdids with axial cross & 1 lateral bar per quadrant; central area relatively narrow (<1/3 the shield width). All 8 holes of similar size..
				Retecapsa schizobrachiata Cretarhabdids with axial cross & 1 lateral bar per quadrant located towards the tips of the cross; central area relatively broad. The 8 central area holes are of unequal size. Medium to large (5-11 µm).
				Axial cross & >1 lateral bar per quadrant
				Retecapsa crenulata Cretarhabdids with axial cross & two lateral bars in each quadrant (delimiting around 12 perforations).
				Retecapsa surirella Cretarhabdids with axial cross & about three lateral bars in each quadrant (delimiting around 16 perforations).
				Retecapsa escaigii Cretarhabdids with axial cross & numerous narrow lateral bars per quadrant. Distal shield flat or sloping into central area.
				No axial cross
				Retecapsa ficula Cretarhabdids with narrow central area entirely closed by bars
				Retecapsa sp. Specimens not identified to species level

Bown&Young1997 f5 03.jpg

Taxonomy:

Citation: Retecapsa Black, 1971

Taxonomic 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.

Taxonomic 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: Retecapsa + * , Heterorhabdus *

Search data:

LITHS: placolith, elliptical, CA: cross-axial, grill, process, ca_disjunct, CROSS-POLARS: R-prominent, rim-unicyclic,

Lith size: 4->11µm;
Data source notes: size range of included species

The morphological data given here can be used on the advanced search page. See also these notes

Geological Range:
Last occurrence (top): at top of Maastrichtian Stage (100% up, 66Ma, in Danian stage). Data source: Total of ranges of the species in this database
First occurrence (base): within NJ8a subzone (175.79-179.53Ma, base in Toarcian stage). Data source: Total of ranges of species in this database

Plot of occurrence data:

Range-bar - range as quoted above, pink interval top occurs in, green interval base occurs in.
Triangles indicate an event for which a precise placement has been suggested
Neptune data: This is a higher taxon page so Neptune data is not plotted. See also: customisable plot Parent: Cretarhabdaceae

References:

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

Bown, P. R. & Cooper, M. K. E. (1998). Jurassic. In, Bown, P. R. (ed.) Calcareous Nannofossil Biostratigraphy. British Micropalaeontological Society Publication Series . 34-85. gs O

Bown, P. R. & Young, J. R. (1997). Mesozoic calcareous nannoplankton classification. Journal of Nannoplankton Research. 19(1): 21-36. gs

Burnett, J. A. (1998). Upper Cretaceous. In, Bown, P. R. (ed.) Calcareous Nannofossil Biostratigraphy. British Micropalaeontological Society Publication Series . 132-199. gs O

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