Nannotax3 - ntax_mesozoic - Conusphaera mexicana

Conusphaera mexicana


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

Distinguishing features:
Parent taxon (Conusphaera): Tapering nannoliths with steeply sloping rim and central area filled with a core of radially arranged elements. Most commonly seen in side view. The rim elements are joined along vertical sutures (protolith-rim-like).
This taxon: 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.


Sub-taxa & variants (time control age-window is: 0-800Ma)
Conusphaera mexicana subsp. mexicana
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.
Conusphaera mexicana subsp. minor
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

Taxonomic 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: C. mexicana *

Distinguishing features:
Parent taxon (Conusphaera): Tapering nannoliths with steeply sloping rim and central area filled with a core of radially arranged elements. Most commonly seen in side view. The rim elements are joined along vertical sutures (protolith-rim-like).
This taxon: 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.

Search data:
TagsLITHS: nannolith-radiate, elliptical, cylindrical, CA: closed, CROSS-POLARS: rim-unicyclic,
MetricsLith size: 3->9µm; Segments: 16->24;
Data source notes: range of sub-species
The morphological data given here can be used on the advanced search page. See also these notes

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:

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(2): 59-69. gs V O

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: Proceedings of the 2nd INA Conference, London 1987. 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 V O

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 V O

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

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 V O


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Conusphaera mexicana compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 28-11-2021

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Short stable page link: https://mikrotax.org/Nannotax3/index.php?id=10270 Go to Archive.is to create a permanent copy of this page - citation notes



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