Nannotax3 - ntax_main - Mesozoic nannofossils

Taxonomic rank: informal high level group

Taxonomic discussion:
This grouping includes all the predominanantly Mesozoic orders and incertae sedis groups.

Mesozoic nannofossils also occur in the Braarudosphaerales (including Braarudosphaeraceae, Nannoconaceae and Polycyclolithaceae), Calciosoleniaceae and Lapideacassaceae.

The Cretaceous/Paleogene extinctions had a massive effect on calcareous nannofossils with virtually all common species becoming extinct, hence it is convenient to separate Mesozoic and Cenozoic nannoplankton. They are not, however, phylogenetically separate groups since there are significant common features between them (e.g. V and R mode calcification in heterococcoliths, Young et al. 1992), and since it is commonly accepted that the Cenozoic orders each originated from Mesozoic precursors (e.g. Perch-Nielsen 1979, Medlin et al. 2008, Bown et al. 2017).
The most important overviews of Mesozoic nannofossils are given by Perch-Nielsen (1985) and in the various chapters in Bown (1998). In addition, Bown & Young (1997) introduce the taxonomy used in Bown (1998), and we largely follow that taxonomy here.

Distinguishing features:
Parent taxon (ntax_main):
This taxon: Predominantly Mesozoic nannofossils - except for Braarudosphaerales

Geological Range:
Last occurrence (top): Extant. Data source: Total of ranges of the species in this database
First occurrence (base): within Carnian Stage (227.30-237.00Ma, base in Carnian stage). Data source: Total of ranges of species in this database

References:

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 O

Bown, P. R. & Young, J. R. (1997). Mesozoic calcareous nannoplankton classification. Journal of Nannoplankton Research. 19(1): 21-36. gs

Bown, P. R. (1998b). Triassic. In, Bown, P. R. (ed.) Calcareous Nannofossil Biostratigraphy. British Micropalaeontological Society Publication Series . 29-33. gs

Bown, P. R., Rutledge, D. C., Crux, J. A. & Gallagher, L. T. (1998). Lower Cretaceous. In, Bown, P. R. (ed.) Calcareous Nannofossil Biostratigraphy. British Micropalaeontological Society Publication Series . 86-131. gs O

Bown, P. R., Lees, J. A. & Young, J. R. (2017). On the Cretaceous origin of the Order Syracosphaerales and the genus Syracosphaera. Journal of Micropalaeontology. 36(2): 153-165. gs

Burnett, J. A. (1998). Upper Cretaceous. In, Bown, P. R. (ed.) Calcareous Nannofossil Biostratigraphy. British Micropalaeontological Society Publication Series . 132-199. gs O

Medlin, L. K., Sáez, A. G. & Young, J. R. (2008). A molecular clock for coccolithophores and implications for selectivity of phytoplankton extinctions across the K/T boundary. Marine Micropaleontology. 67(1-2): 69-86. gs

Perch-Nielsen, K. (1979). Calcareous nannofossils from the Cretaceous between the North Sea and the Mediterranean. In, Weidmann, J. (ed.) Aspekte der Kreide Europas. International Union of Geological Sciences Series A . 6: 223-272. gs O

Perch-Nielsen, K. (1985). Mesozoic calcareous nannofossils. In, Bolli, H. M., Saunders, J. B. & Perch-Nielsen, K. (eds) Plankton Stratigraphy. Cambridge University Press, Cambridge (1): 329-426. 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

Daughter taxa (time control age-window is: 0-800Ma)		Granddaughter taxa
	Heterococcoliths
	Arkhangelskiales Tiered placoliths with 3-5 closely-appressed shields.	Arkhangelskiellaceae Kamptneriaceae
	Eiffellithales Murolith coccoliths with an upper/outer cycle of clockwise-imbricate V-units and a lower/inner cycle of R-units.	Chiastozygaceae Cenozoic Chiastozygaceae Eiffellithaceae Rhagodiscaceae
	Stephanolithiales Murolith coccoliths with a distal/outer cycle of non-imbricating elements, i.e., in side view, the sutures are vertical or near-vertical.	Parhabdolithaceae Stephanolithiaceae
	Podorhabdales Placolith (or modified placolith) coccoliths showing little or no imbrication. Typically, V-units form distal shield, R-units form proximal shield.	Axopodorhabdaceae Biscutaceae Calyculaceae Cretarhabdaceae Mazaganellaceae Prediscosphaeraceae Tubodiscaceae
	Watznaueriales Placolith (or modified placolith) coccoliths with a distal cycle of clockwise-imbricating elements. R-units well developed, forming proximal and distal shield elements with opposite senses of imbrication; V-units typically form a narrow distal cycle near the inner edge of the shield.	Watznaueriaceae
	Mesozoic Heterococcoliths inc sedis Heterococcolith genera which do not show characteristic features of any of the well-established families.	Unidentified Mesozoic heterococcoliths globular inc sedis muroliths inc sedis placoliths inc sedis planoliths inc sedis spine fragments
	Holococcoliths & Nannoliths
	Mesozoic Holococcoliths Coccoliths formed of minute (ca 0.1µm) rhombohedral micro-crystals. Often a life-cycle stage with heterococcolith counterpart(s).	Common genera Rarer genera
	Mesozoic nannoliths inc sedis Nannofossils not obviously homologous with heterococcoliths, holococcoliths, or braarudosphaeralids	Eoconusphaeraceae Microrhabdulaceae Nannoliths inc sed - radiate multielement Nannoliths inc sed - other
	Mesozoic Calcispheres inc sed Calcispheres and other non-coccoliths found in nannofossil preps. Some taxa previously placed here have been moved to the calcareous dinoflagellates pages [Feb 2017].	Schizosphaerellaceae Prinsiosphaera Carnicalyxia Cassianospica

Mesozoic nannofossils

References:

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