Nannotax3 - ntax_main - Discoaster bollii

Citation: Discoaster bollii Martini & Bramlette, 1963

Variants:

D. bollii long arm
D. bollii short arm

There is considerable variation in the ratio of central area width to arm length within D. bollii and Browning et al. (2017) record that long and short armed forms are routinely differentiated in their work. However, they also recorded that the two forms have identical ranges and intergrade and so they treated them as a single species.
They do recommend separating specimens with reduced numbers of rays as separate species, see table above. Other workers may prefer to use informal labels for these or to combine them in D. bollii.

Distinguishing features:
Parent taxon (D. exilis group):
This taxon: Similar to D. exilis but with large distal boss, small proximal boss, and wide central-area, and usually smaller (<10µm).

10-14 µm according to the original description and this is typical of observed specimens, i.e. very large specimens do not seem to occur.

Geological Range:
Last occurrence (top): in lower part of NN10 zone (20% up, 9.3Ma, in Tortonian stage). Data source: Browning et al. 2017
First occurrence (base): near base of NN9 zone (10% up, 10.4Ma, in Tortonian stage). Data source: Browning et al. 2017

References:

Bergen, J. A. (1984). Calcareous nannoplankton from Deep Sea Drilling Project Leg 78A: evidence for imbricate underthrusting at the Lesser Antillian active margin. Initial Reports of the Deep Sea Drilling Project. 78A: 411-445. gs

Browning, E., Bergen, J. A., Blair, S. A., Boesiger, T. M. & de Kaenel, E. (2017). Late Miocene to Late Pliocene taxonomy and stratigraphy of the genus Discoaster in the circum North Atlantic Basin: Gulf of Mexico and ODP Leg 154. Journal of Nannoplankton Research. 37(2-3): 189-214. gs

de Kaenel, E. & Villa, G. (1996). Oligocene-Miocene calcareous nannofossil biostratigraphy and paleoeecology from the Iberian Abyssal Plain. Proceedings of the Ocean Drilling Program, Scientific Results. 149: 79-145. gs O

Martini, E. & Bramlette, M. N. (1963). Calcareous nannoplankton from the experimental Mohole drilling. Journal of Paleontology. 37(4): 845-855. gs

Müller, C. (1974). Calcareous nannoplankton, Leg 25 (Western Indian Ocean). Initial Reports of the Deep Sea Drilling Project. 25: 579-633. gs

Perch-Nielsen, K. (1972). Remarks on Late Cretaceous to Pleistocene coccoliths from the North Atlantic. Initial Reports of the Deep Sea Drilling Project. 12: 1003-1069. gs

Salomon, R. (1999). The Calcite Palace. Website - https://ina.tmsoc.org/galleries/CalcitePalace/index.htm. -. gs

Theodoridis, S. (1984). Calcareous nannofossil biostratigraphy of the Miocene and revision of the helicoliths and discoasters. Utrecht Micropaleontological Bulletin. 32: 1-271. gs O

Varol, O. & Bowman, A. R. (2024). The new Middle Miocene genus Olladiscoaster, and related and associated discoasters. Grzybowski Foundation Special Publication. 28: 1-102. gs

Varol, O. (2025). A practical guide to optical studies of calcareous nannofossils. Grzybowski Foundation Special Publication. 29: 1-222. gs

Wei, W. (2003). Upper Miocene nannofossil bistratigraphy and taxonomy of Exxon core CH30-43-2 from the Gulf of Mexico. Journal of Nannoplankton Research. 25(1): 17-23. gs

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

forms with different numbers of rays (time control age-window is: 0-800Ma)
				Discoaster pentabollii 5-rayed D. bollii
				Discoaster quadribollii 4-rayed D. bollii
				Discoaster tribollii 3-rayed D. bollii

Discoaster bollii

References:

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