Rhabdosphaera

Cenozoic Taxa

Rhabdosphaera vitrea (Deflandre in Deflandre & Fert, 1954) Bramlette & Sullivan, 1961

Edited by Lyndsey on Fri, 11/03/2011 - 17:34

Rhabdosphaera vitrea (Deflandre in Deflandre & Fert, 1954) Bramlette & Sullivan, 1961

Description: Rhabdoliths with a very narrow styliform spine that typically has a prominent basal collar. In LM the coccolith is broad and thin, and dominated by the inner cycle, with the outer cycle forming only the outermost edge. SEM images show the four buttress-like structures at the base of the spine, which appear as a "collar" in LM. It also appears that R. vitrea lacks the radial lath cycle characteristic of Blackites, hence the inclusion within the genus Rhabdosphaera.

Remarks:

Geological Time Data

Geological Time Periods:

NP23

NP14

Biblio Reference:

Varol, O. 1998. Palaeogene. Calcareous nannofossil biostratigraphy. :200-224.

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81 reads
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Neogene: Rhabdosphaera
Paleogene: Rhabdosphaera vitrea

Rhabdosphaera Haeckel, 1894

Submitted by Jeremy Young on Fri, 06/02/2009 - 12:13

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88 reads
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Neogene: Rhabdosphaera
Paleogene: Rhabdosphaera

Zygrhablithus bijugatus

Edited by Lyndsey on Thu, 10/03/2011 - 14:02

Zygrhablithus bijugatus (Deflandre in Deflandre and Fert, 1954) Deflandre, 1959 [Zygolithus]

Description: Large rod-shaped holococcolith with small basal disk.

Remarks: In well-preserved material (E.g. Bown 2005) it can be seen that these are cavate holococcoliths, i.e. they have an internal cavity. Usually howevr with overgrowth this cavitiy is filled and the holococcolith develops nirregular form.

Original description:

Synonyms (list from Aubry 1988):

Isthmolithus claviformis Bronnimann & Stradner 1960
Lucianorhabdus dispar Stradner 1961
Pseudozygrhablithus altus Haq 1971
Pseudozygrhablithus latus Haq 1971
Pseudozygrhablithus comprimus Haq 1971
Rhabdosphaera semiformis Bramlette & Sullivan 1961
Sujkowskiella enigmatica Hay Mohler & Wade 1966

Of these I. claviformis, S. enigmatica and R. semiformis were all based on isolated half or quarter specimens of Z. bijugatus.

Geological Time Data

Geological Time Periods:

NN1

Paleogene

Biblio Reference:

Young, JR. 1998. Neogene. Calcareous nannofossil biostratigraphy. :225-265.

Notes on occurrence information:

This species is also rarely seen in NN2 (see de Kaenel and Villa, 1996).

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1111 reads
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Neogene: Rhabdosphaera; Zygrhablithus; Zygrhablithus bijugatus; Holococcoliths

Rhabdosphaera clavigera

Edited by Lyndsey on Thu, 10/03/2011 - 11:22

Rhabdosphaera clavigera Murray & Blackman 1898

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.

Fossil specimens:

	LM of typical R. clavigera
	SEM of R. styiifera morphotype
	distal view of non spine-bearing coccolith
	proximal view of non spine-bearing coccolith

Original description:

Variants:

Rhabdosphaera clavigera var. stylifera (Lohmann, 1902) Kleijne and Jordan, 1990 - form with narrow,
parallel-sided, spine. NB Aubry & Kahn (2006) have provided strong evidence that clavigera and stylifera are discrete species, with clavigera being larger as well as more robust. However in the fossil record only the clavigera type is commonly preserved.

Rhabdosphaera procera Martini, 1969 - delicate form, similar to Rh. c. stylifera; Rhabdosphaera sicca (Stradner, 1963).

Geological Time Data

Geological Time Periods:

NN21

NN4

Biblio Reference:

Young, JR. 1998. Neogene. Calcareous nannofossil biostratigraphy. :225-265.

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580 reads
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Neogene: Rhabdosphaera; Rhabdosphaera clavigera

Discosphaera tubifera

Edited by Lyndsey on Thu, 10/03/2011 - 11:19

Discosphaera tubifera (Murray & Blackman 1898) Ostenfeld 1900 [Rhabdosphaera]

Extant coccolithophore: The only described species of Discosphaera; characterised by monomorphc coccosphere with all coccoliths bearing trumpet-like protrusions (see also generic description). Common in oligotrophic surface waters.

Fossil record: Never common but specimens occur consistently in well-preserved sub-tropical sediments. Usually the base is detached but appearance of trumpet-like processes is distinctive in LM (see images).

Original description:

Geological Time Data

Geological Time Periods:

Holocene

NN11

Biblio Reference:

Young, JR. 1998. Neogene. Calcareous nannofossil biostratigraphy. :225-265.

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466 reads
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Neogene: Discosphaera; Discosphaera tubifera; Rhabdosphaera

Rhabdosphaera

Edited by Lyndsey on Tue, 01/03/2011 - 17:04

Genus Rhabdosphaera Haeckel, 1894

Coccosphere: Dimorphic with inner spine-bearing and outer non spine-bearing coccoliths, distributed around coccosphere. Usually non-motile and no differentiation of circum-flagella coccoliths but occasional cells with flagella have been observed (Lohmann 1902, Probert pers. comm.).

Coccoliths: Radial cycle absent, lamellar cycle fills central area and forms spine.

Type species: R. clavigera.

Synonym: Rhabdolithus Kamptner ex Deflandre in Grassé 1952.

Variant: Palusphaera -similar to Rhabdosphaera but monomorphic, all coccoiths have spines. in the fossil record these would be included in Rhabdosphaera

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1133 reads
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Neogene: Rhabdosphaera

Rhabdosphaeraceae

Edited by Lyndsey on Tue, 01/03/2011 - 16:55

Family RHABDOSPHAERACEAE Haeckel 1894

Coccospheres: Motile or non-motile, typically with spine-bearing and non-spine-bearing coccoliths with similar shields, but polymorphic, varimorphic and monomorphic genera also occur. The spine-bearing coccoliths may be confined to the poles or distributed around the coccosphere, greatly increasing its outer diameter.

Coccoliths: Typically disc-shaped (planoliths) and formed of three components.

1. Rim: narrow; slightly elevated; formed of two cycles of elements. A. Upper/outer rim cycle of simple non-imbricate elements (Kleijne 1992), these are V-units (our LM obs.). B. Lower/inner rim cycle showing strong obliquity. Crystallographic orientation uncertain.

2. Radial cycle - joins rim to central lamellar cycle; radial laths, of equal number to rim units; slits often present between the laths (absent in Rhabdosphaera and Saturnulus).

3. Lamellar cycle(s) - lamellar elements showing clockwise imbrication, often multiple cycles with inner cycles more elongate, inclined and in helical arrangement forming spine or protrusion. May end in a “cuneate cycle” of a few well-formed elements.

References: Extant species are reviewed by Norris (1984), Kleijne (1992), Aubry (1999), Cros & Fortuño (2002), Young et al. (2003).

Fossil record: Most extant Rhabdosphaeraceae are very small and, apart from R. clavigera, are rarely recorded in the fossil record. There is, however, a diverse and abundant group of larger Rhabdosphaeraceae in the Eocene (see Perch-Nielsen 1985b; Varol 1989; Shafik 1989; Aubry 1999, Bown 2005).

Original description:

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1368 reads
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Neogene: Rhabdosphaera; Rhabdosphaeraceae

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