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Helicosphaera

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Cenozoic Taxa

Zygodiscales

Edited by Jeremy Young on Fri, 11/03/2011 - 18:50

Order ZYGODISCALES Young & Bown 1997

yes

zyg

 
Taxa included: The extant families Helicosphaeraceae and Pontosphaeraceae and extinct Family Zygodiscaceae. These show highly variable shape, but similar structure, and there is strong palaeontological evidence for their evolutionary connections (Romein 1979; Aubry 1989).

 

   Helicosphaeraceae
   Pontosphaeraceae
 

Zygodiscaceae

(Palaeogene only)
  • Ciphragmolithus
  • Isthmolithus
  • Lophodolithus
  • Neochiastozygus
  • Neococcolithites
  • Zygodiscus

 

Coccolith structure: V-units form outer rim; in Pontosphaeraceae, this is a narrow cycle of anticlockwise-imbricating elements, in the Helicosphaeraceae, a helical flange. The R-units form a proximal plate of rather regular, inward-growing elements and a distal blanket, which typically appears as a mass of minute, tangentially-elongated crystallites. Growth does not occur downwards from the proto-coccolith ring and so the alternating belt of V-R nuclei remains clearly visible on the proximal surface.

Life-cycles and culture studies: Helicosphaera carteri and H. wallichii have been cultured repeatedly (Inouye pers. comm.; Probert & Houdan 2004) and Scyphosphaera apsteinii once (Probert & Houdan 2004). No life-cycle transitions have been observed in these cultures, but combination coccospheres have been observed for Helicosphaera (Cros et al. 2000; Geisen et al. 2002), Pontosphaera and Scyphosphaera (Frada et al. 2008). These indicate that the haploid phase forms holococcoliths with distinctive rhomboid-array ultrastructure (formerly included in the genus Syracolithus).  

Geological Time Data
Geological Time Periods: 
NN21
Paleocene
Biblio Reference: 
Young, JR.  1998.  Neogene. Calcareous nannofossil biostratigraphy. :225-265.

Helicosphaera carteri

Edited by Jeremy Young on Wed, 09/03/2011 - 18:22

Helicosphaera carteri (Wallich, 1877) Kamptner, 1954 [Coccosphaera]

Description: The most common Helicosphaera species. Medium to large size, flange ends in wing, two pores in central-area.

Remarks:

Original description:

Coccosphaera carterii 020241.jpgCoccosphaera carterii 020242.jpg

Synonym: H. kamptneri (Hay and Mohler in Hay et al., 1967) Locker, 1973 [Helicopontosphaera]. NB This was an alternative name suggested by Hay et al. (1967) on the grounds that the original descrition of Coccosphaera carteri was likely to have been based on a completely different coccolithophore. This also lead them to propose Helicopontosphaera as an alternative name for the genus. Jafar & Martini (1975) showed this was incorrect, and so that Helicosphaera carteri was the correct name for the species.

Variants

:

  • H. carteri var. burkei (Black, 1971) Theodoridis, 1984 - central-area closed;
  • H. carteri var. hyalina (Gaarder, 1970) Jordan and Young, 1990 - central-area closed;
  • H. acuta Theodoridis, 1984 - no true wing, slight inverse orientation of openings;
  • H. colombiana (Gartner, 1977) Haq and Berggren, 1978 - smaller wing;
  • H. neogranulata (Gartner, 1977) Haq and Berggren, 1978 - central-area with no true pores/granular;
  • H. paleocarteri Theodoridis, 1984 - with small pores separated from the extinction line.

paleocarteri_Theod84.jpgacuta_Theod84.jpg

Geological Time Data
Geological Time Periods: 
NN21
NN 1
Biblio Reference: 
Young, JR.  1998.  Neogene. Calcareous nannofossil biostratigraphy. :225-265.

Helicosphaera wilcoxonii (Gartner, 1971) Jafar & Martini, 1975

Edited by Paul Bown on Tue, 11/05/2010 - 12:00

Description: Helicosphaera with relatively wide central area spanned by a broad tranverse to slightly-oblique disjunct bar and a flange that ends in a spur.

Remarks:

Range: NP17 to NP21.

Helicosphaera seminulum Bramlette & Sullivan, 1961

Edited by Paul Bown on Tue, 11/05/2010 - 11:58

Description: Elliptical Helicosphaera with relatively wide central area spanned by a broad tranverse to slightly-oblique disjunct bar.

Remarks: Probably intergrades with Helicosphaera bramlettei.

Range: NP13 to NP23.

Helicosphaera reticulata Bramlette & Wilcoxon, 1967

Edited by Paul Bown on Tue, 11/05/2010 - 11:56

Description: Broadly rhombohedral Helicosphaera with a moderately well-developed spur in some specimens and a broad, oblique (high angled) disjunct bar. Distal surface covered by a blanket with multiple perforations, some large.

Remarks:

Range: NP15b to NP21.

Helicosphaera lophota (Bramlette & Sullivan, 1961) Locker, 1973

Edited by Paul Bown on Tue, 11/05/2010 - 11:54

Description: Elliptical, oblong or reniform Helicosphaera with wide flange and central area spanned by a broad, near-longitudinal disjunct bar with distinct median suture.

Remarks:

Range: NP14 to NP17.

Helicosphaera ethologa Bown, 2005

Edited by Paul Bown on Tue, 11/05/2010 - 11:51

Description: Large Helicosphaera with flange ending in a wing. Rather diffuse blanket image in XPL and closed central area or two narrow near-longitundinal slits.

Remarks: Similar to Neogene Helicosphaera carteri, hence the previous informal designation as Helicosphaera aff. H. carteri by de Kaenel & Villa (1996), but its stratigraphic range is distinctly different and the wing is somewhat less strongly developed.

Range: NP23 to NP24.

Holotype: Paratype:

Helicosphaera ethologa pl13-18.JPGHelicosphaera ethologa pl13-16.JPGHelicosphaera ethologa pl13-17.JPG Helicosphaera ethologa pl13-19.JPGHelicosphaera ethologa pl13-20.JPG

Helicosphaera compacta Bramlette & Wilcoxon, 1967

Edited by Paul Bown on Tue, 11/05/2010 - 11:47

Description: Elliptical Helicosphaera with well defined birefringent blanket in XPL and narrow central area spanned by a conjunct bar.

Remarks:

Range: NP16 to NP24.

Helicosphaera clarissima Bown, 2005

Edited by Paul Bown on Tue, 11/05/2010 - 11:46

Description: Large elliptical to almond-shaped Helicosphaera with well defined birefringent blanket in XPL and a central area spanned by a broad, oblique, disjunct birefringent bar.

Remarks:

Range: NP16 to NP17.

Holotype: Paratype:

Helicosphaera clarissima pl11-33.JPGHelicosphaera clarissima pl11-34.JPGHelicosphaera clarissima pl11-35.JPG Helicosphaera clarissima pl11-30.JPG

Helicosphaera bramlettei (Müller, 1970) Jafar & Martini, 1975

Edited by Paul Bown on Tue, 11/05/2010 - 11:43

Description: Elliptical Helicosphaera with relatively wide central area spanned by a broad, oblique disjunct bar.

Remarks:

Range: NP14 to NP23.

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