Conusphaera mexicana


Classification: Mesozoic -> Nannoliths inc sedis -> Eoconusphaeraceae -> Conusphaera -> Conusphaera mexicana
Sister taxa: C. mexicana, C. rothii, C. maledicto, C. sinespina, C. sp.,

Distinguishing features: Tapering nannoliths with steeply sloping rim and central area filled with a core of radially arranged elements, which in LM shows relatively uniform birefringence with an axial extinction line. Most commonly seen in side view.


Daughter taxa: (blue => in age window 0-800Ma)
Tall (height >4 microns) tapering nannoliths with steeply sloping rim and central area filled with a core of radially arranged elements, which in LM shows relatively uniform birefringence with an axial extinction line. Most commonly seen in side view.
Short (height <4 microns) tapering nannoliths with steeply sloping rim and central area filled with a core of radially arranged elements, which in LM shows relatively uniform birefringence with an axial extinction line. Seen in plan and side view.

Taxonomy:

Citation: Conusphaera mexicana Trejo, 1969
Rank: Species
Notes & discussion: Short (height <4 microns: Conusphaera mexicana minor) and tall (height >4 microns: Conusphaera mexicana mexicana) subspecies are distinguished. Tethyan distribution.

Farinacci & Howe catalog pages: Conusphaera mexicana *

Distinguishing features: Tapering nannoliths with steeply sloping rim and central area filled with a core of radially arranged elements, which in LM shows relatively uniform birefringence with an axial extinction line. Most commonly seen in side view.


Ecology & Biogeography: Tethyan distribution.

Geological Range:
Notes: Most commonly recorded in the Tithonian. Last occurrence Aptian according to Bergen (1994).
Last occurrence (top): within NJ18 zone (145.01-148.35Ma, top in Tithonian stage). Data source: [PRB rough estimate]
First occurrence (base): within NJ17a subzone (149.09-151.50Ma, base in Tithonian stage). Data source: Bown & Cooper 1998

Plot of occurrence data:

  • (NB There is no histogram as there are no occurrence records for the taxon in the Neptune database) Parent: Conusphaera

    References:

    Bergen, J. A. (1994). Berriasian to early Aptian calcareous nannofossils from the Vocontian Trough (SE France) and Deep Sea Drilling Site 534: new nannofossil taxa and a summary of low-latitude biostratigraphic events. Journal of Nannoplankton Research. 16: 59-69. gs

    Bown, P. R. & Cooper, M. K. E. (1989a). Conical nannofossils in the Mesozoic. In, Crux, J. A. & van Heck, S. E. (eds) Nannofossils and their applications. British Micropalaeontological Society Publication Series. 98-106. gs

    Bown, P. R. & Cooper, M. K. E. (1998). Jurassic. In, Bown, P. R. (ed.) Calcareous Nannofossil Biostratigraphy. British Micropalaeontological Society Publication Series. 34-85. gs

    Bralower, T. J., Monechi, S. & Thierstein, H. R. (1989). Calcareous nannofossil zonation of the Jurassic-Cretaceous boundary interval and correlation with the geomagnetic polarity timescale. Marine Micropaleontology. 14: 153-235. gs

    Covington, J. M. & Wise, S. W. (1987). Calcareous nannofossil biostratigraphy of a Lower Cretaceous deep-sea fan complex: Deep Sea Drilling Project Leg 93 Site 603, lower continental rise off Cape Hatteras. Initial Reports of the Deep Sea Drilling Project. 93: 617-660. gs

    de Kaenel, E. & Bergen, J. A. (1996). Mesozoic calcareous nannofossil biostratigraphy from sites 897, 899, and 901, Iberia Abyssal Plain: New biostratigraphic evidence. Proceedings of the Ocean Drilling Program. Scientific Results. 149: 27-59. gs

    Grün, W. & Allemann, F. (1975). The Lower Cretaceous of Caravaca (Spain): Berriasian Calcareous Nannoplankton of the Miravetes Section (Subbetic Zone, Prov. of Murcia). Eclogae Geologicae Helvetiae. 68: 147-211. gs

    Jakubowski, M. (1986). New calcareous nannofossil taxa from the Lower Cretaceous of the North Sea. INA Newsletter. 8: 38-42. gs

    Trejo, M. (1969). Conusphaera mexicana, un nuevo coccolitoforido del Jurassico Superior de Mexico. Revista del Instituto Mexicano del Petroleo. 1: 5-15. gs

    Wind, F. H. & Cepek, P. (1979). Lower Cretaceous calcareous nannoplankton from DSDP Hole 397A (northwest African Margin). Initial Reports of the Deep Sea Drilling Project. 47A: 221-235. gs


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    Conusphaera mexicana compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 13-11-2019

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