Umbilicosphaera


Classification: ntax_cenozoic -> Coccolithales -> Calcidiscaceae -> Umbilicosphaera
Sister taxa: Calcidiscus, Hayaster, Oolithotus, Umbilicosphaera, Cryptococcolithus, Hayella

Daughter taxa (time control age-window is: 0-800Ma)Granddaughter taxa
extant and Pliocene species
Umbilicosphaera anulus
Coccoliths elliptical, rims narrow

Umbilicosphaera foliosa
Coccoliths circular; central area narrow, distal shield larger than proximal shield; proximal shield bicyclic

Umbilicosphaera hulburtiana
Coccoliths elliptical, otherwise similar to U. foliosa

Umbilicosphaera sibogae
Coccoliths circular; central area wide; distal shield smaller than proximal shield; proximal shield unicyclic. Coccospheres can be very large

Neogene species
Umbilicosphaera jafari
Small circular species of Umbilicosphaera with narrow central-area. Distal shield slightly wider than proximal shield.

Umbilicosphaera rotula
Coccoliths with wide central-area and narrow rim. Shields of similar size

Palaeogene species - circular
Umbilicosphaera bramlettei
Small to medium sized (3.5-7.5 µm), ring-shaped coccoliths with narrow shields (distinctly bicyclic in XPL) and a wide, open central-area. The two cycles are similar in width; the bright inner cycle is crossed by non-axial extinction lines.

Umbilicosphaera jordanii
Medium sized (3.5-6.0 µm) circular ring-shaped placoliths with a non-birefringent distal shield, a narrow bright tube cycle crossed by non-axial extinction lines, and vacant central area that is slightly wider than the shields.

Umbilicosphaera protoannulus
Small to medium sized (4.5-8.0 µm) ring-shaped coccoliths that are distinctly bicyclic in XPL: the bright inner cycle is narrower than the outer cycle, and crossed by extinction lines that are near axial.

Palaeogene species - elliptical
Umbilicosphaera detecta
Medium to large (~5-9 microns), elliptical placolith coccoliths with narrow bicyclic rim (in XPL) and wide, apparently vacant, central area. The rim width is around half that of the central area (rim width/central area width: 0.5-0.7).

Umbilicosphaera edgariae
Medium to large (~5-10µm), broadly elliptical placolith coccoliths with broad bicyclic rim (in XPL) and vacant central area. The rim width is similar to, or slightly greater than, that of the central area (rim width/central area width: 1.0-1.4).

Umbilicosphaera henrikseniae
Medium sized (6-7 µm) elliptical placolith with a non-birefringent distal shield and vacant central area approximately the same width as the shields.

Umbilicosphaera sp.
Specimens which cannot be assigned to established species

Taxonomy:

Citation: Umbilicosphaera Lohmann, 1902
Rank: Genus
Type species: Umbilicosphaera mirabilis Lohmann 1902 (j. syn. of U. sibogae).
Synonyms: Geminilithella Backman, 1980 - the type species U. rotula falls well within the range of variation shown by modern Umbilicosphaera species.
Taxonomic discussion:

The separation of Calcidiscus and Umbilicosphaera is essentially based on width of central opening, which is not a very satisfactory criterion, but so far molecular genetic data has supported separation of the extant species assigned to these genera (Saez et al. 2003). The larger size of the central opening also means that the proto-coccolith ring is relatively wide in Umbilicosphaera and so that the numbers of elements for a given coccolith size is higher in Umbilicosphaera and so they are narrower and less clearly visible in LM. In LM the individual elements are usually clearly visible in Calcidiscus species, especially in phase contrast illumination, whilst they are obscure in Umbilicosphaera. Umbilicosphaera species usually also show complex kinking of sutures in the distal shield, but this can occur in Calcidiscus.

Neogene species: U. sibogae, U. foliosa and U. hulburtiana are all clearly recognisable at least in Late Pleistocene sediements and they almost certainly evolved from the Miocene species U. jafari and U. rotula. However, the detailed evolutionary history has not been studied.

Paleogene species: Bown et al. (2007) showed that some Palaeogene species were virtually identical to modern/Neogene Umbilicosphera, paticuary U. jordanii. Subsequently Young & Bown (2014) have recombined several more Paleoene species with wide central areas into Umbilicosphaera - based on the arbitrary criterion of central area width is >25% of coccolith width (i.e. distal shield width < 1.5 x central area width). This does allow a consistent morphotaxonomy but may not reflect phylogeny.

Distinguishing features: Central area open

Farinacci & Howe catalog pages: Umbilicosphaera * , Geminilithella * , Cycloplacolithus * , Cycloplacolithella *


Morphology: Coccoliths circular or elliptical, with Calcidiscus structure but central area open, distal shield elements usually show complex kinked sutures. Proximal shield may be monocyclic (e.g. U. sibogae, U. rotula) or bicyclic (e.g. U. foliosa, U. hulburtiana) and may be larger or smaller than the distal shield.

Search data:
TagsLITHS: placolith, circular, elliptical, CA: vacant,
CSPH: equant, monomorphic, CROSS-POLARS: rim-bicyclic, V-prominent, R-prominent,
MetricsLith size: 3->10µm; Coccosphere size: 8->30µm;
The morphological data given here can be used on the advanced search page. See also these notes

Geological Range:
Last occurrence (top): Extant Data source: Total of range of species in this database
First occurrence (base): in upper part of Danian Stage (63% up, 63.2Ma, in Danian stage). Data source: Total of range of species in this database

Plot of occurrence data:

References:

Backman, J. (1980). Miocene-Pliocene nannofossils and sedimentation rates in the Hatton-Rockall Basin, NE Atlantic Ocean. Stockholm Contributions in Geology. 36: 1-91. gs

Bown, P. R., Dunkley-Jones, T. & Young, J. R. (2007). Umbilicosphaera jordanii Bown 2005 from the Paleogene of Tanzania: confirmation of generic assignment and a Paleocene origination for the family Calcidiscaceae. Journal of Nannoplankton Research. 29(1): 25-30. gs V O

Lohmann, H. (1902). Die Coccolithophoridae, eine Monographie der Coccolithen bildenden Flagellaten, zugleich ein Beitrag zur Kenntnis des Mittelmeerauftriebs. Archiv für Protistenkunde. 1: 89-165. gs V O

Sáez, A. G., Probert, I., Geisen, M., Quinn, P., Young, J. R. & Medlin, L. K. (2003). Pseudo-cryptic speciation in coccolithophores. Proceedings of the National Academy of Sciences, USA. 100(12): 7163-7168. gs

Young, J. R. & Bown, P. R. (2014). Some emendments to calcareous nannoplankton taxonomy. Journal of Nannoplankton Research. 33(1): 39-46. gs V O


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Umbilicosphaera compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 1-3-2021

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Short stable page link: https://mikrotax.org/Nannotax3/index.php?id=1460 Go to Archive.is to create a permanent copy of this page - citation notes



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