Distinguishing features: Varimorphic; liths placolith-like but with helical shield structure; arranged in spiral on coccosphere
| Daughter taxa: (blue => in age window 0-300Ma) | Granddaughter taxa | ||||
| | | | Coccoliths with helical flange; arranged spirally on the coccosphere | |
Taxonomy:
Farinacci & Howe catalog pages: Helicosphaeraceae [no catalog entry yet]
Distinguishing features: Varimorphic; liths placolith-like but with helical shield structure; arranged in spiral on coccosphere
Morphology remarks: Coccospheres ellipsoidal with a prominent flagellar opening. Coccoliths arranged spirally round the coccosphere and may vary slightly in size and shape from the antapex to the flagellar pole.
Coccolith structure - Outer rim (V-units) of the coccoliths are modified into a helical flange, ending in a wing or spike. R-units form the baseplate and extend to form blanket of small elements (Young et al. 2004). Central-area bars may be conjunct, disjunct or absent. Theodoridis (1984) discusses the structure.
| Tags | LITHS: placolith, RIM: wing, CSPH: ellipsoidal, varimorphic, V-UNITS: distal shield, R-UNITS: blanket, c-str, px-plate, DETAILS: rim-bicyclic, isogyres kinked, isogyres oblique, isogyres separated, |
| Metrics | Lith size: 4->22µm; Sources: |
Geological Range:
Last occurrence (top): Extant Data source: Total of range of species in this database
First occurrence (base): in lower part of Ypresian Stage (28% up, 53.7Ma, in Ypresian stage). Data source: Total of range of species in this database
Plot of occurrence data:
Black, M., (1971). The systematics of coccoliths in relation to the paleontological record. In: Funnell, B.M. and Riedel, W.R. (Editors), The Micropaleontology of the Oceans. Cambridge University Press, Cambridge, pp. 611-624. Perch-Nielsen, K., (1985). Cenozoic calcareous nannofossils. In: Bolli, H.M., Saunders, J.B. and Perch-Nielsen, K. (Editors), Plankton Stratigraphy. Cambridge University Press, Cambridge, pp. 427-555. Theodoridis, S., (1984). Calcareous nannofossil biostratigraphy of the Miocene and revision of the helicoliths and discoasters. Utrecht Micropaleontological Bulletin, 32: 1-271. Young, J.R.; Henriksen, K. & Probert, I., (2004). Structure and morphogenesis of the coccoliths of the CODENET species. In: Thierstein, H.R. and Young, J.R. (Editors), Coccolithophores - From molecular processes to global impact. Springer, pp. 191-216.References:
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Helicosphaeraceae compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 16-11-2018
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