Chiasmolithus


Classification: Coccolithophores -> Coccolithales -> Coccolithaceae -> Chiasmolithus
Sister taxa: Coccolithus, Bramletteius, Campylosphaera, Chiasmolithus, Coronocyclus, Cruciplacolithus, Ericsonia, Solidopons, Birkelundia, Clausicoccus, Craticullithus, Hughesius, Kilwalithus,

Daughter taxa: (blue => in age window 0-800Ma) Granddaughter taxa
Upper-tube cycle strongly developed; cross bars with complex construction, median exinction line

Upper-tube cycle weakly developed; cross bars with simple construction, no median exinction line

Specimens which cannot be assigned to any established species

Taxonomy:

Citation: Chiasmolithus Hay et al., 1966
Rank: Genus
Type species: Chiasmolithus oamaruensis (Deflandre, 1954) Hay et al., 1966
Notes & discussion: Chiasmolithus has been subdivided into two lineages by several authors (Gartner 1970; Romein 1979; Perch-Nielsen, 1985; Varol, 1992), one including coccoliths with broad upper-tube cycles (bright in XPL) and cross bars with median extinction lines, and the other having narrower upper-tube cycles and simple, narrow cross bars. We distinguish these here as the Chiasmolithus bidens and C. consuetus groups respectively, after co-occuring Palaeocene species which illustrate this divison well. Varol (1992) recommended separating the two groups as genera and proposed the new name Sullivania for the group separated here as the C. consuetus group. This proposal has not been widely followed but does have obvious merit, and certainly should be followed if the genus is shown to be polyphyletic as Romein (1979) and Perch-Nielsen (1985) suggested.

Distinguishing features: Placolith coccoliths with Coccolithus-type shields and tube, but with disjunct diagonal cross bars spanning the central area.

Farinacci & Howe catalog pages: Chiasmolithus + *

Search data:
TagsLITHS: placolith, elliptical, RIM: inner-tube-broad, psh-bicyclic, CA: cross, cross-diagonal-symmetric,
CSPH: spherical, monomorphic, V-UNITS: distal shield, px-tube, R-UNITS: c-str, ds-tube, prox shield, DETAILS: cstr-w-median-ext-line, ca_disjunct, rim-bicyclic, isogyres oblique,
MetricsLith size: 5->24µm;
Sources:
The morphological data given here can be used on the advanced search page. See also these notes

Geological Range:
Last occurrence (top): in upper part of Chattian Stage (73% up, 24.4Ma, in Chattian stage). Data source: Total of range of species in this database
First occurrence (base): in lower part of Danian Stage (28% up, 64.8Ma, in Danian stage). Data source: Total of range of species in this database

Plot of occurrence data:

References:

Gartner, S. (1970). Phylogenetic lineages in the Lower Tertiary genus Chiasmolithus. Proceedings of the North American Paleontological Convention, September 1969. G(930-957): -. gs

Hay, W. W., Mohler, H. P. & Wade, M. E. (1966). Calcareous nannofossils from Nal'chik (northwest Caucasus). Eclogae Geologicae Helvetiae. 59: 379-399. gs

Perch-Nielsen, K. (1985a). Cenozoic calcareous nannofossils. In, Bolli, H. M. , Saunders, J. B. & Perch-Nielsen, K. (eds) Plankton Stratigraphy. Cambridge University Press, Cambridge 427-555. gs

Romein, A. J. T. (1979). Lineages in Early Paleogene calcareous nannoplankton. Utrecht Micropaleontological Bulletin. 22: 231-. gs

Varol, O. (1992a). Sullivania a new genus of Palaeogene coccoliths. Journal of Micropalaeontology. 11: 141-150. gs


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Chiasmolithus compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 20-9-2019

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Short stable page link: http://mikrotax.org/Nannotax3/index.php?id=262 Go to Archive.is to create a permanent copy of this page - citation notes



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