Distinguishing features: Placoliths or modified placoliths with R-unit well developed, forming proximal and distal shield elements with opposite senses of imbrication; the V-unit typically forms a narrow distal cycle near the inner edge of the shield. Central-area structures are typically disjunct. Birefringent LM image, in which the V-unit cycle appears only as a thin, dark line.
| Daughter taxa: (blue => in age window 0-800Ma) | Granddaughter taxa | ||||
| Regular placoliths | |||||
| | | | Elliptical watznaueriacean coccoliths with broad V-unit cycle, which results in a three tiered placolith structure. Moderately birefringent in XPL. | |
| | | | Circular watznaueriacean coccoliths. | |
| | | | Modified watznaueriacean coccoliths with one conical/flaring (proximal) shield with elements joined along oblique sutures, and a smaller, flatter (distal) shield with the principle elements joined along near radial sutures. Usually circular with a central opening. | |
| | | | Elliptical watznaueriacean coccoliths typically with central-area axial cross, with or without additional lateral bars. Cross usually spine bearing. Extinction figure with nearly straight arms. | |
| | | | Elliptical watznaueriacean coccoliths with central-areas that are typically closed or narrow but may be spanned by transverse bar, bars or grill. Extinction figure with clearly inflected arms. | |
| Elevated taxa | |||||
| | | | Watznaueriacean coccoliths with a tube-like/conical proximal shield. | |
| | | | High, cylindrical morphology with a peg-like distal cycle; possibly the isolated central part of Cyclagelosphaera deflandrei specimens which have lost the shields. | |
| | | | Medium to large, barrel-shaped coccoliths that are highly-birefringent and seen in both side and plan view. | |
Taxonomy:
Farinacci & Howe catalog pages: Watznaueriaceae [no catalog entry yet]
Distinguishing features: Placoliths or modified placoliths with R-unit well developed, forming proximal and distal shield elements with opposite senses of imbrication; the V-unit typically forms a narrow distal cycle near the inner edge of the shield. Central-area structures are typically disjunct. Birefringent LM image, in which the V-unit cycle appears only as a thin, dark line.
Morphology remarks: Coccoliths are highly birefringent in XPL. Common, sometimes dominant, through most of the Mesozoic (Pliensbachian to Maastrichtian).
| Tags | LITHS: placolith, |
| Metrics | Lith size: 0->0µm; Sources: |
Geological Range:
Last occurrence (top): in lower part of Ypresian Stage (22% up, 54.2Ma, in Ypresian stage). Data source: Total of range of species in this database
First occurrence (base): at base of Pliensbachian Stage (0% up, 190.8Ma, in Pliensbachian stage). Data source: Total of range of species in this database
Plot of occurrence data:
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 :: :: Reinhardt, P. (1964). Einige Kalkflagellaten-Gattungen (Coccolithophoriden, Coccolithineen) aus dem Mesozoikum Deutschlands. Monatsberichte der Deutschen Akademie der Wissenschaften zu Berlin. 6: 749-759. gs :: :: Rood, A. P., Hay, W. W. & Barnard, T. (1971). Electron Microscope Studies of Oxford Clay Coccoliths. Eclogae Geologicae Helvetiae. 64: 245-272. gs :: view :: openReferences:
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Watznaueriaceae compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 13-7-2020
Short stable page link: http://mikrotax.org/Nannotax3/index.php?id=11314 Go to Archive.is to create a permanent copy of this page - citation notes |