 27.jpg)
| Daughter taxa: (blue => in age window 0-800Ma) | Granddaughter taxa | ||||
| | | | Eliptical or circular; central area open or with simple bar or weak axial cross | |
| | | | Like Cruciplacolithus but coccoliths small and with large, thin, paddle-like processes. | |
| | | | Like Cruciplacolithus but the coccoliths are longitudinally arched and typically near parallel sided, and so appear oblong in outline | |
| | | | Placolith coccoliths with Coccolithus-type shields and tube, but with disjunct diagonal cross bars spanning the central area. | |
| | | | Coccoliths ring-shaped without discrete shields | |
| | | | Coccolith central area spanned by disjunct axial cross that may be rotated by up to 20 degrees. | |
| | | | Coccolithus-like coccoliths that are typically circular and have broad upper tube elements that dominate the distal shield. The dominance of the R-unit cycle results in a bright LM XPL image that is distinct from Coccolithus. | |
| | | | Rim narrow and central area spanned by an elevated bridge | |
| Genera with central grill or plate | |||||
| | | | Central area covered by perforate plate which appears uniformly dark in xpl | |
| | | | Rim structure like Coccolithus; perforate plate covers the central area on the distal side | |
| | | | Placolith coccoliths with a wide central-area typically spanned by multi-element lattice-like grills or imperforate plates. | |
| | | | Placolith coccoliths showing low birefringence with central area filled by 2 to 4 plates. Lacks a clearly birefringent distal tube cycle | |
| | | | Placolith coccoliths, typically small (c. 3 microns), with central-area spanned by a finely perforate net. The distal shield is typically bicyclic and the rim structure appears to be coccolithacean. | |
Taxonomy:
Distinguishing features: Liths with R-unit extending from proximal shield to form upper/inner tube-cyle. Mostly elliptical
Farinacci & Howe catalog pages: Coccolithaceae [no catalog entry yet]
Morphology remarks: Heterococcoliths are placoliths with rim structure similar to Coccolithus: V-unit forms both distal shield and lower cycle of central-area; R-unit forms both proximal shield and upper cycle of central-area. The proximal shield itself is bicyclic with distinct upper and lower layers but these are both formed from the R-unit. The central-area is often spanned by disjunct structures and these are used to define various fossil genera (see e.g. Perch-Nielsen 1985, Young & Bown 1997,Young & Henriksen 2003).
Biology & life-cycles: Modern Coccolithus pelagicus has a holococcolith stage
| Tags | LITHS: placolith, elliptical, RIM: psh-bicyclic, CSPH: spherical, monomorphic, V-UNITS: distal shield, px-tube, R-UNITS: c-str, ds-tube, prox shield, DETAILS: isogyres oblique, |
| Metrics | Lith size: 8->12µm; Sources: |
Geological Range:
Last occurrence (top): Extant Data source: Total of range of species in this database
First occurrence (base): at base of Danian Stage (0% up, 66Ma, in Danian stage). Data source: Total of range of species in this database
Plot of occurrence data:
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 Poche, F. (1913). Das System der Protozoa. Archiv für Protistenkunde. 30: 125-321. gs Young, J. R. & Bown, P. R. (1997a). Cenozoic calcareous nannoplankton classification. Journal of Nannoplankton Research. 19(1): 36-47. gs Young, J. R. & Henriksen, K. (2003). Biomineralization within vesicles: the calcite of coccoliths. Reviews in Mineralogy and Geochemistry. 54: 189-215. gsReferences:
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Coccolithaceae compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 16-12-2019
Short stable page link: http://mikrotax.org/Nannotax3/index.php?id=313 Go to Archive.is to create a permanent copy of this page - citation notes |