Nannotax3 - ntax_mesozoic

Nannotax3 - ntax_mesozoic - Discorhabdus

Discorhabdus

Classification: ntax_mesozoic -> Podorhabdales -> Biscutaceae -> Discorhabdus
Sister taxa: Biscutum, Discorhabdus, Similiscutum ⟩⟨ Boletuvelum, Chiastella, Crucibiscutum, Gaarderella, Gephyrobiscutum, Helicorhabdus, Jimenezberrocosoia, Seribiscutum, Sollasites

Distinguishing features:
Parent taxon (Biscutaceae): Regular placoliths; rim broad, central area relatively narrow, with variable central structures.
The distal shield is formed from V-units and the proximal shield and tube cycle are formed from R-units.
This taxon: Circular, shields broad, usually without a prominent inner tube cycle; central-area typically narrow, may contain a spine.

Daughter taxa (time control age-window is: 0-800Ma)
				Discorhabdus biradiatus Discorhabdus with gaps between distal shield elements
				Discorhabdus corollatus Small Discorhabdus with narrow central area from which a tall, narrow spine protrudes.
				Discorhabdus criotus Discorhabdus with a narrow, distal inner cycle, narrow/closed central area and distal shield sutures that kink near the shield's outer edge. Bicyclic rim image.
				Discorhabdus hannibalis Small (3-5 µm), with two closely appressed shields; proximal shield is wider than the distal shield, protruding beyond it and is at least twice as thick as the distal shield in side view.
				Discorhabdus ignotus Small to medium-sized Discorhabdus with closed central area that may or may not contain a spine.
				Discorhabdus patulus Placoliths with a tall flaring spine.
				Discorhabdus striatus Medium to large Discorhabdus with closed central area.
				Discorhabdus watkinsii Species with low broad open protrusion and reduced proximal shield,
				Discorhabdus sp. Specimens not identified to species level

Taxonomy:

Citation: Discorhabdus Noël, 1965

Rank: Genus

Type species: Rhabdolithus patulus Deflandre, 1954.

Synonyms: Bidiscus Bukry 1969 - widely used in the literature
Cenorbiculus Burns 1976

Farinacci & Howe catalog pages: Discorhabdus + * , Cenorbiculus * , Bidiscus *

Search data:

Tags	LITHS: placolith, circular, CA: process, closed, CROSS-POLARS: rim-bicyclic, V-prominent,
Metrics	Lith size: 3->8µm; 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 range of species in this database
First occurrence (base): in lower part of Toarcian Stage (27% up, 180.4Ma, in Toarcian stage). Data source: Total of range 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: Biscutaceae

References:

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

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

Noël, D. (1965b). 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. 1-209. gs