Nannotax3 - ntax_cenozoic - Rhabdosphaera clavigera

Citation: Rhabdosphaera clavigera Murray & Blackman, 1898

Basionym: Rhabdosphaera claviger Murray & Blackman, 1898

Synonyms:

Clavosphaera furonculata Lecal-Schlauder 1951
Discolithus phaseolus Black and Barnes 1961 (based on isolated body coccolith without spine)
Discolithus pirenus Kamptner 1967 (based on isolated body coccolith without spine)
Rhabdosphaera murrayi Ostenfeld 1899
Rhabdosphaera tignifer Schiller (1913) [my interpretation - JRY 2015]
Rhabdosphaera otwayensis Rade (1977) [my interpretation - JRY 2015]

Variants:

Rhabdosphaera procera Martini, 1969 - delicate form, similar to Rh. c. stylifera;
Rhabdosphaera sicca (Stradner, 1963) Fuchs & Stradner 1977 - tapering rather than parallel sided

Taxonomic discussion: Forms with club-shaped (clavigera) and narrower parallel-sided (stylifera) spines are often separated as varieties of R. clavigera. However the two types intergrade and both can be found on single coccospheres, suggesting this is an example of degree of calcification variation rather than genotypic variation. Conversely, Kahn & Aubry (2006) provided strong evidence that the clavigera and stylifera morphotypes can form discrete populations, with clavigera being larger as well as more robust - spine lenth 7-9µm vs. 3-5µm. They concluded that they should be regarded as separate species. This division often works and smaller specimens do tend to have more delicate spines - but intermediates also occur, so retaining the taxa as varieties seems sensible.
In the plankton the stylifera variety is dominant but in the fossil record the clavigera variety is more commonly preserved.

Distinguishing features:
Parent taxon (Rhabdosphaera): Coccoliths without radial lath cycle; coccospheres dimorphic, only some spine-bearing
This taxon: Spine with pentameral structure

Coccosphere: Spherical, usually non-motile but occasionally with flagella (Lohmann 1902, Probert unpubl.). Dimorphic with spine-bearing and spine-less coccoliths.
Coccoliths: Spines robust, formed of five clockwise-spiral sets of elements with pentameral terminal papilla. Base of coccoiths elliptical/oblong, 3-3.5 µm. Spine-bearing liths with wider rim than non spine-bearing liths.
In LM core of spine appears to be hollow, coccolith base is often missing but spine form is very characteristic.
Spine structure is analysed in detial by Locht et al. 2014.

Never succesfully grown in culture - it has frequently been isolated but does not grow (Probert pers. comm.). Possible combination coccospheres with Sphaerocalyptra quadridentata illustrated by Cros et al. 2000

Geological Range:
Notes: Common in the Late Miocene and Pliocene rather rarely recorded in older sediments. Dunkley Jones et al. 2009 illustrated a rhabdosphaera spine with the classic R. clavigera structure from sediments of NP19-20 age
Last occurrence (top): Extant. Data source: present in the plankton (Young et al. 2003)
First occurrence (base): within NN4 zone (14.91-17.95Ma, base in Burdigalian stage). Data source: Young (1998)

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

Fuchs, R. & Stradner, H. (1977). Uber Nannofossilien im Badenien (Mittelmiozan) der zentralen Paratethys. Beitrage zur Paläontologie von Österreichs. 2: 1-58. gs

Kahn, A. & Aubry, M. -P. (2006). Intraspecific morphotypic variability in the Family Rhabdosphaeraceae. Micropaleontology. 52(4): 317-342. gs

Kamptner, E. (1967). Kalkflagellaten - Skelettreste aus Tiefseeschlamm des Südatlantischen Ozeans. Annalen des Naturhistorischen Museums in Wien. 71: 117-198. gs O

Kleijne, A. (1992). Extant Rhabdosphaeraceae (coccolithophorids, class Prymnesiophyceae) from the Indian Ocean, Red Sea, Mediterranean Sea and North Atlantic Ocean. Scripta Geologica. 100: 1-63. gs

Locht, R. van de, Slater, T. J. A., Verch, A., Young, J. R., Haigh, S. J. & Kröger, R. (2014). Ultrastructure and crystallography of nanoscale calcite building blocks in Rhabdosphaera clavigera coccolith spines. Crystal Growth & Design. 14: 1710-1718. gs

Martini, E. (1969). Nannoplankton aus dem Miozän von Gabon (Westafrika). Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen. 132: 283-300. gs

Murray, G. & Blackman, V. H. (1898). On the nature of the Coccospheres and Rhabdospheres. Philosophical Transactions of the Royal Society of London. 190(1): 427-441. gs

Rade, J. (1977). Tertiary biostratigraohic zonation based on calcareous nannoplankton in eastrn Australian nearshore basins. Micropaleontology. 23(3): 270-296. gs

Stradner, H. (1963). New contributions to Mesozoic stratigraphy by means of nannofossils. In, Proceedings of the Sixth World Petroleum Congress. Section 1 Paper 4: 167-183. gs

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

Rhabdosphaera clavigera

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Sub-taxa & variants (time control age-window is: 0-800Ma)
				Rhabdosphaera clavigera var. clavigera Spine with pentameral structure - robust, club-shaped, 7-10µm long
				Rhabdosphaera clavigera var. stylifera Spine with pentameral structure - narrow, parallel-sided, 3-5µm long