Nannotax3 - ntax_mesozoic - Syracosphaerales

Distinguishing features:
Parent taxon (ntax_mesozoic): Mesozoic nannofossils - Cenozoic and extant taxa are in a separate module
This taxon: Heterocococcoliths with central area including a cycle of radial laths alternating with rim elements but with tangential c-axis orientations

Citation: Syracosphaerales Hay 1977, emend Young et al. 2003

Taxonomic discussion: The Order Syracosphaerales has not generally been used in the Mesozoic; however, the Calciosoleniaceae occur in the Cretaceous, where it shows affinities with the families Stephanolithiaceae and Parhabdolithaceae, which have been classified in the Order Stephanolithiales Bown & Young, 1997. The Calciosolenia specimens seen in the Mesozoic are identical to those in the Cenozoic, and they have a continuous record across the K/Pg boundary, so are clearly the same taxon and need to be classified in the same higher taxonomic group. Therefore, the Syracosphaerales already does occur in the Mesozoic and it appears increasingly likely that it evolved from the Stephanolithiaceae. This leaves the question of whether there is strong enough evidence to transfer the families Stephanolithiaceae and Parhabdolithaceae into the Syracosphaerales, which would make the Order Stephanolithiales redundant. Whilst we think the balance of probabilities is that the Syracosphaerales evolved from the Stephanolithiaceae, we do not have a problem with using paraphyletic taxa, and we are strongly aware both of the value of stability in nomenclature and of the likelihood of new evidence from molecular genetics and/or study of exceptionally-preserved coccoliths from other time intervals. As a general rule, we believe that taxonomic reorganization should be based on conclusive evidence and we feel it is sensible to follow this principle here. So we retain the traditional classification. [Bown et al. 2017]

Geological Range:
Last occurrence (top): Extant. Data source: Total of ranges of the species in this database
First occurrence (base): within Early Hauterivian Substage (133.09-133.88Ma, base in Hauterivian stage). Data source: Total of ranges of species in this database

References:

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

Hay, W. W. (1977). Calcareous nannofossils. In, Ramsay, A. T. S. (ed.) Oceanic Micropalaentology. Academic Press, London 1055-1200. 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

Syracosphaerales

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Daughter taxa (time control age-window is: 0-800Ma)		Granddaughter taxa
	Calciosoleniaceae	Calciosolenia
	Syracosphaeraceae	Syracosphaera