Nannotax3 - ntax_main - Umbellosphaera tenuis

Citation: Umbellosphaera tenuis (Kamptner 1937) Paasche, in Markali & Paasche 1955

Basionym: Coccolithus tenuis * Kamptner 1937

Taxonomic discussion:

This form is substantially more robust than U. irregularis and is much more common in the fossil record.

Distinguishing features:
Parent taxon (Umbellosphaera): Coccoliths trumpet-shaped
This taxon: Coccoliths convex outwards, relatively heavily calcified, with ridges on the distal surface.

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.

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.

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 O

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

Kamptner, E. (1937). 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). PhD Thesis, Vrije Universiteit Amsterdam. 1-321. gs

Markali, J. & Paasche, E. (1955). On two species of Umbellosphaera, a new marine coccolithophorid genus. Nytt Magasin for Botanikk. 4: 95-100. gs

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

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

Samtleben, C. (1978). Pliocene-Pleistocene coccolith assemblages from Sierra Leone Rise - Site 366, Leg 41. Initial Reports of the Deep Sea Drilling Project. 41(16): 913-931. gs

Yang, T. -N., Wei, K. & Wu, J. -T. (2012). Marine coccolithophores around Taiwan. Biodiversity Research Center, Academica Sinica, Taipei. 1-96. gs

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

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. S1: 1-132. gs

Sub-taxa & variants (time control age-window is: 0-800Ma)		Granddaughter taxa
	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 III Sutural and secondary ridges heavily calcified	Umbellosphaera tenuis type IIIa Umbellosphaera tenuis type IIIb
	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. irregularis in distal view but have the characteristic convex profile of U. tenuis. Liths are often very thin/weakly calcified.

Umbellosphaera tenuis

References:

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