-19.JPG)
-83.JPG)
Distinguishing features: Extant coccolithophores and Cenozoic calcareous nannofossils - Mesozoic nannofossils are in a separate module
| Daughter taxa: (blue => in age window 0-300Ma) | Granddaughter taxa | ||||
| Heterococcoliths | |||||
| | | | Heterococcoliths mostly placoliths with R-unit dominant. Motile phases with vestigial haptonema. | |
| | | | Mostly placolith heterococcoliths, with V-unit forming the distal shield; R-unit the proximal shield. | |
| | | | Heterococcoliths with V-units forming upper/outer cycle of imbricated elements and R-units forming basal plate and central mass of irregular elements | |
| | | | Coccoliths with radial lath cycle of T-units, and disjunct, often complex, axial structure, coccospheres often polymorphic | |
| | | | Various heterococcolith groups not obviously related to the well-defined orders | |
| | | | Mesozoic taxa which occur in low abundances in the early Palaeogene. | |
| Holococcoliths & Nannoliths | |||||
| | | | Haploid life-cycle stages, with liths formed of numerous rhombohedral microcrystals | |
| | | | Diploid (?) life-cycle stage covered by pentaliths (plates formed of 5 segments with lamellar sub-structure) formed extracellualrly | |
| | | | Radially symmetrical nannoliths formed from one to several separate cycles of elements that radiate from a common centre or axis. | |
| | | | Haptophytes forming calcareous structures not obviously homologous with heterococcoliths, holococcoliths, or discoasteralids | |
| | | | | |
Taxonomy:
There are complications however, most obviously, typical coccolithophores have haplo-diplontic life-cycles with different coccoliths produced in haploid and diploid phases. The diploid phase heterococcoliths have complex structures formed of radial arrays of interlocking crystal units usually with alternating vertical and radial crystallographic orientations (V/R model). The different rim-structures of these heterococcoliths form the essential basis of the classification. The haploid phase holococcoliths are beautifully organised arrays of rhombohedral crystallites, but their morphology is relatively plastic and does not yield useful phylogenetic data. Finally, some other nannofossils occur which do not obviously fit either the heterococcolith or holococcolith model and these are conventionally refered to as nannoliths.
Understanding the classification of coccolithophores thus requires some basic knowledge of coccolithophore life-cycles, biomineralisation, crystallography and optical mineralogy (to interpret cross-polarised light images). A useful overview is provided by Bown & Young (1998) and other references which help explain the system applied here are listed below.
Farinacci & Howe catalog pages: Coccolithophores [no catalog entry yet]
Distinguishing features: Extant coccolithophores and Cenozoic calcareous nannofossils - Mesozoic nannofossils are in a separate module
Search data:| Tags | |
| Metrics | Lith size: 0->0µm; Sources: |
Geological Range:
Last occurrence (top): Extant Data source: Total of range of species in this database
First occurrence (base): at top of No known fossil record modern (100% up, 0Ma, in stage). Data source: Total of range of species in this database
Plot of occurrence data:
Bown, P.R. & Young, J.R., (1998). Introduction - calcareous nannoplankton biology. In: Bown, P.R. (Editor), Calcareous nannofossil biostratigraphy. British Micropalaeontological Society Publication Series. Chapman & Hall, pp. 1-15. Young, J.R.; Didymus, J.M.; Bown, P.R.; Prins, B. & Mann, S., (1992). Crystal assembly and phylogenetic evolution in heterococcoliths. Nature, 356: 516-518. Young, J.R. & others, (1997). Guidelines for coccolith and calcareous nannofossil terminology. Palaeontology, 40: 875-912. Young, J.R.; Davis, S.A.; Bown, P.R. & Mann, S., (1999). Coccolith ultrastructure and biomineralisation. Journal of Structural Biology, 126: 195-215. Young, J.R.; Geisen, M.; Cros, L.; Kleijne, A.; Probert, I. & Ostergaard, J.B., (2003). A guide to extant coccolithophore taxonomy. Journal of Nannoplankton Research, Special Issue, 1: 1-132. Young, J.R.; Geisen, M. & Probert, I., (2005). A review of selected aspects of coccolithophore biology with implications for palaeobiodiversity estimation. Micropaleontology, 51(4): 267-288.References:
 |
Cenozoic and Modern Coccolithophores compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 16-12-2018
|