Nannotax3 - ntax_cenozoic - Isochrysidales

Citation: Isochrysidales Pascher, 1910

Taxonomic discussion: Grouping of the Prinsiaceae and Noelaerhabdaceae is based on coccolith structure and stratophenetic data (Young et al. 1992; Young & Bown 1997). Grouping of the Isochrysidaceae and Noelaerhabdaceae is based on flagellar characters (haptonema vestigial), this was questioned by (Green & Jordan 1994) but has been strongly supported by biochemical characters (production of alkenones) and molecular genetics (Edvardsen et al. 2000; Fujiwara et al. 2001; Sáez et al. 2004). The order Isochrysidales Pascher 1910 is used for these three families instead of Prinsiales Young & Bown, 1997, since it has priority.

Distinguishing features:
Parent taxon (ntax_cenozoic): Extant coccolithophores and Cenozoic calcareous nannofossils - Mesozoic nannofossils are in a separate module
This taxon: 2N: Mostly placolith heterococcoliths with R-unit dominant. Non-motile
N: non-calcifying, motile, with vestigial haptonema.

Coccoliths are placoliths, but unlike the Coccolithaceae, growth does not occur downward from the proto-coccolith ring. The R-unit is always well developed, forming a proximal shield element, two tube-elements with opposite senses of imbrication, and usually a central-area element. The locus of the proto-coccolith ring is usually marked by a ring of slits on the proximal surface. Central-area structures are always conjunct, being formed from either the central-area element or the inner tube-element of the proximal shield. In the Prinsiaceae, the V-unit is well developed (Toweius-type structure); forming an upper layer to the proximal shield, an outermost tube and the distal shield. In the Noelaerhabdaceae, the V-unit is virtually absent (Reticulofenestra-type structure) and the outer of the two R-unit tube-cycles is extended to form the distal shield.
References: Young et al. 1991; Young et al. 2004,

Geological Range:
Last occurrence (top): Extant. Data source: Total of ranges of the species in this database
First occurrence (base): within CC26 zone (66.04-67.82Ma, base in Maastrichtian stage). Data source: Total of ranges of species in this database

References:

Edvardsen, B., Eikrem, W., Green, J. C., Andersen, R. A., Moon-Van Der Staay, S. Y. & Medlin, L. K. (2000). Phylogenetic reconstructions of the Haptophyta inferred from 18S ribosomal DNA sequences and available morphological data. Phycologia. 39: 19-35. gs

Fujiwara, S., Tsuzuki, M., Kawachi, M., Minaka, N. & Inouye, I. (2001). Molecular phylogeny of the haptophyta based on the rbcL gene and sequence variation in the spacer region of the RUBISCO operon. Journal of Phycology. 37: 121-129. gs

Green, J. C. & Jordan, R. W. (1994). Systematic history and taxonomy. In, Green, J. C. & Leadbeater, B. S. C. (eds) The Haptophyte Algae. Systematics Association Special Volume . 51(1): 1-21. gs

Pascher, A. (1910). Chrysomonaden aus dem Hirschberger Grossteiche. Monographien und Abhandlungen zur Internationalen Revue der gesamten Hydrobiologie und Hydrographie. 1: 66-. gs

Perch-Nielsen, K. (1985). Cenozoic calcareous nannofossils. In, Bolli, H. M., Saunders, J. B. & Perch-Nielsen, K. (eds) Plankton Stratigraphy. Cambridge University Press, Cambridge (1): 427-555. gs

Sáez, A. G., Probert, I., Young, J. R., Edvardsen, B., Wenche, E. & Medlin, L. K. (2004). A review of the phylogeny of the Haptophyta. In, Thierstein, H. R. & Young, J. R. (eds) Coccolithophores - from molecular processes to global impact. Springer, Berlin 251-270. gs

Young, J. R. & Bown, P. R. (1997). Cenozoic calcareous nannoplankton classification. Journal of Nannoplankton Research. 19(1): 36-47. gs

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. gs

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. S1: 1-132. gs

Young, J. R., Henriksen, K. & Probert, I. (2004b). Structure and morphogenesis of the coccoliths of the CODENET species. In, Thierstein, H. R. & Young, J. R. (eds) Coccolithophores - From molecular processes to global impact. Springer, Berlin 191-216. gs O

Daughter taxa (time control age-window is: 0-800Ma)		Granddaughter taxa
	Noelaerhabdaceae Heterococcoliths with Reticulofenestra-type structure, V-units vestigal, R-units forming grill, both shields, and two-layered tube	Emiliania Gephyrocapsa Pseudoemiliania Reticulofenestra Noelaerhabdus Bekelithella Pyrocyclus
	Prinsiaceae Placoliths with R-units forming the lower layer of proximal shield, inner tube and middle tube; V-units forming an upper layer to the proximal shield, outermost tube and the distal shield. In LM they display a dark outer cycle and brighter inner cycle. Central-area structures are conjunct, formed from the R-units.	Futyania Praeprinsius Prinsius Toweius Neobiscutum Hornibrookina
	Isochrysidaceae Non-calcifying Isochrysidales	Dicrateria Isochrysis Ruttnera Tisochrysis

Isochrysidales

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