Umbellosphaera tenuis


Classification: ntax_cenozoic -> Coccolith families inc sed -> Umbellosphaeraceae -> Umbellosphaera -> Umbellosphaera tenuis
Sister taxa: U. tenuis, U. irregularis, U. sp.

Daughter taxa (time control age-window is: 0-800Ma)
Umbellosphaera tenuis type I
Coccoliths with distinct sutural ridges and numerous finer papillate secondary ridges
Umbellosphaera tenuis type II
Sutural and secondary ridges papillate.
Umbellosphaera tenuis type IIIa
Sutural and secondary ridges heavily calcified and not clearly separable. Central area closed by inward extensions of the sutural rides.
Umbellosphaera tenuis type IIIb
Sutural and secondary ridges heavily calcified but well-separated, 2-4 secondary ridges per element. Central area open.
Umbellosphaera tenuis type IV
Sutural ridges well calcified near centre of coccolith, lower toward periphery. Numerous secondary ridges, often anastamosing.
Umbellosphaera tenuis type O
Cocoliths smooth - resemble U. irregulars in distal view but have the characteristic convex profile of U. tenuis. Liths are often very thin/weakly calcified.

Taxonomy:

Citation: Umbellosphaera tenuis (Kamptner 1937) Paasche in Markali & Paasche, 1955
Rank: Species
Basionym: Coccolithus tenuis Kamptner 1937
Synonyms:
Variants: Variation: The morphology of this species is very variable, in terms of ridge thickness, presence of papillae (nodes) on the ridges, number of secondary ridges, degree of bimodality in ridge thickness. Kleijne (1993) distinguished several types of U. tenuis. This work has not been followed up by a detailed study and these types are arguably intergradational. Nonetheless, most specimens are readily assignable to a single type, so it seems possible that they will prove to be discrete (sub) species. (NB Subdivision of type II into IIa Iand IIb is from Young et al. 2003)
Taxonomic discussion: This form is substantially more robust than U. irregularis and is much more common in the fossil record.

Distinguishing features: Coccoliths convex outwards, relatively heavily calcified, with ridges on the distal surface.

Farinacci & Howe catalog pages: C. tenuis * , E. lidzi * , D. murrayi *


Morphology: Liths convex distally; distal surface usually with pattern of ridges; major ridges sub-radial running along sutures; secondary ridges diverge anticlockwise from them.
Proxmil shield is normally narrow, often missing, and dificult to detect in LM.

Search data:
TagsLITHS: placolith, asymmetric, elliptical, CA: ca_conjunct, plate, closed,
CSPH: equant, BC-dimorphic, CROSS-POLARS: rim-unicyclic, R-prominent,
MetricsLith size: 2->9µm; Coccosphere size: 8->12µm; Liths per sphere: 15->25
Data source notes: lith size from Kleijne 1993; lith numbers from Yang & Wei 2003, range inferred from single estimate
The morphological data given here can be used on the advanced search page. See also these notes

Geological Range:
Notes: U. tenuis is much less common in Holocene sediments than in the plankton, probably because the coccoliths readily disintegrate and dissolve. They are nonetheless reasonably frequent in the Quaternary, but there are few pre-Pliocene records. It is conceivable that they have become more abundant since extinction of the discoasters which may have occupied a similar ologitrophic niche.
Last occurrence (top): Extant Data source: present in the plankton (Young et al. 2003)
First occurrence (base): within NN15 zone (3.70-3.92Ma, base in Zanclean stage). Data source: Young (1998)

Plot of occurrence data:

References:

Black, M. & Barnes, B. (1961). Coccoliths and discoasters from the floor of the South Atlantic Ocean. Journal of the Royal Microscopical Society. 80: 137-147. gs

Boudreaux, J. E. & Hay, W. W. (1969). Calcareous nannoplankton and biostratigraphy of the late Pliocene-Pleistocene-Recent sediments in the Submarex cores. Revista Española de Micropaleontología. 1(3): 249-292. gs

Heimdal, B. R. & Gaarder, K. R. (1981). Coccolithophorids from the northern part of the eastern central Atlantic II. Heterococcolithophorids. “Meteor” Forschungsergebnisse, Reihe D, Biologie. 33: 37-69. gs

Kamptner, E. (1937b). Neue und bemerkenswerte Coccolithineen aus dem Mittelmeer. Archiv für Protistenkunde. 89: 279-316. gs

Kleijne, A. (1993b). Morphology, Taxonomy and distribution of extant coccolithophorids (Calcareous nannoplankton). Drukkerij FEBO B.V., Katwijk. 1-321. gs

Müller, C. (1974b). Calcareous nannoplankton, Leg 25 (Western Indian Ocean). Initial Reports of the Deep Sea Drilling Project. 25: 579-633. gs V O

Reid, F. M. H. (1980). Coccolithophorids of the North Pacific Central Gyre with notes on their vertical and seasonal distribution. Micropaleontology. 26(2): 151-176. gs

Young, J. R. (1998). Neogene. In, Bown, P. R. (ed.) Calcareous Nannofossil Biostratigraphy. British Micropalaeontological Society Publication Series. 225-265. gs V O

Young, J. R., Geisen, M., Cros, L., Kleijne, A., Probert, I. & Ostergaard, J. B. (2003). A guide to extant coccolithophore taxonomy. Journal of Nannoplankton Research, Special Issue. 1: 1-132. gs V O


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Umbellosphaera tenuis compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 27-2-2021

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