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Citation: Pyrocyclus Hay & Towe 1962

Type species: Pyrocyclus inversus Hay and Towe, 1962

Synonyms: Bicolumnus Wei & Wise 1990 [according to Young & Bown 1997]
Amithalithina Pospichal & Wise 1990 [my interpretation JRY 2015]

Taxonomic discussion: These are preservational artefacts and the genus name Pyrocyclus should not be used. It is included here simply to document what people have meant when they used the name. [my interpretation - JRY 2023]

Distinguishing features:
Parent taxon (Noelaerhabdaceae): Heterococcoliths with Reticulofenestra-type structure, V-units vestigal, R-units forming grill, both shields, and two-layered tube
This taxon: Spurious genus for reticulofenestrid coccoliths without shields

This genus was described from the Eocene, but many authors, have ascribed Neogene specimens to it. Backman (1980) described them as coccoliths with a single shield composed of two cycles; a lower cycle of numerous steeply imbricate elements and an upper cycle of fewer tabular elements. In the LM these specimens have a Reticulofenestra-type extinction cross, but with a bright outer rim (in Reticulofenestra the shields are darker than the inner parts of the coccolith, since they are thinner). However, reticulofenestrid coccoliths which have lost most of their shields, leave central cores identical to “Pyrocyclus”. Also, “Pyrocyclus” coccoliths always occur with reticulofenestrids with central-areas of similar size, and shape. This suggests that the “Pyrocyclus” specimens are relict reticulofenestrid cores, or in some cases proto-coccolith rings (Young 1998).
Bicolumnus is a similar form but larger and with a closed central area, it is co-eval with R. scrippsae from which it is presumably derived (Young & Bown 1997).

Geological Range:
Last occurrence (top): at top of (100% up, 0Ma, in "Holocene" stage). Data source: Total of ranges of the species in this database
First occurrence (base): within (-Ma, base in "Holocene" stage). Data source: Total of ranges of species in this database

References:

Backman, J. (1980). Miocene-Pliocene nannofossils and sedimentation rates in the Hatton-Rockall Basin, NE Atlantic Ocean. Stockholm Contributions in Geology. 36: 1-91. gs O

Bukry, D. (1971b). Cenozoic calcareous nannofossils from the Pacific Ocean. San Diego Society of Natural History Transactions. 16: 303-327. gs

Hay, W. W. & Towe, K. M. (1962a). Electron microscope examination of some coccoliths from Donzacq (France). Eclogae Geologicae Helvetiae. 55: 497-517. gs O

Hay, W. W., Mohler, H. P., Roth, P. H., Schmidt, R. R. & Boudreaux, J. E. (1967). Calcareous nannoplankton zonation of the Cenozoic of the Gulf Coast and Caribbean-Antillean area, and transoceanic correlation. Transactions of the Gulf-Coast Association of Geological Societies. 17: 428-480. gs O

Pospichal, J. J. & Wise, S. W. (1990). Paleocene to Middle Eocene calcareous nannofossils of ODP sites 689 and 690, Maud Rise, Weddell Sea. Proceedings of the Ocean Drilling Program, Scientific Results. 113: 613-638. gs

Wei, W. & Wise, S. W. (1990). Middle Eocene to Pleistocene calcareous nannofossils recovered by Ocean Drilling Program leg 113 in the Weddell Sea. Proceedings of the Ocean Drilling Program, Scientific Results. 113: 639-666. gs

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

Young, J. R. (1998). Neogene. In, Bown, P. R. (ed.) Calcareous Nannofossil Biostratigraphy. British Micropalaeontological Society Publication Series . 225-265. gs

Pyrocyclus

References:

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Daughter taxa (time control age-window is: 0-800Ma)
				Pyrocyclus sp. Spurious species for reticulofenestrid specimens without shields