Nannotax3 - ntax_cenozoic - Toweius magnicrassus

Citation: Toweius magnicrassus (Bukry, 1971) Romein, 1979

Basionym: Coccolithus magnicrassus Bukry, 1971

Distinguishing features:
Parent taxon (Toweius): Typically medium-sized.(5-8 µm), elliptical to circular, central areas typically with a conjunct net and/or bars.
This taxon: Large to very large (8-15 µm); broadly elliptical to sub-circular; central area narrow.

According to original description 16-20 microns; however Romein (1979) suggested size range of 10-16 µm and subsequently illustrated specimens have been in this range. Likewise Wei et al. (1993) gave a size range of 8-14.5 µm, with a smaller size at high altitudes (8-11 µm) than at low latitudes (9.5-14.5 µm). This is still the largest known Toweius species.

Most likely ancestor: Toweius callosus - at confidence level 3 (out of 5). Data source: Wei et al. 1993 - fig.6 and discussion.

Geological Range:
Last occurrence (top): within NP14 zone (46.29-49.11Ma, top in Lutetian stage). Data source: Perch-Nielsen 1985b
First occurrence (base): within NP11 zone (53.70-54.17Ma, base in Ypresian stage). Data source: Perch-Nielsen 1985

References:

Bown, P. R. & Newsam, C. (2017). Calcareous nannofossils from the Eocene North Atlantic Ocean (IODP Expedition 342 Sites U1403–1411). Journal of Nannoplankton Research. 37(1): 25-60. gs O

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

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

Romein, A. J. T. (1979). Lineages in Early Paleogene calcareous nannoplankton. Utrecht Micropaleontological Bulletin. 22: 1-231. gs O

Self-Trail, J. (2011). Paleogene Calcareous Nannofossils of the South Dover Bridge core, Southern Maryland (USA). Journal of Nannoplankton Research. 32(1): 1-28. gs

Self-Trail, J. M., Powars, D. S., Watkins, D. K. & Wandless, G. A. (2012). Calcareous nannofossil assemblage changes across the Paleocene–Eocene Thermal Maximum: Evidence from a shelf setting. Marine Micropaleontology. 92–93: 61-80. gs

Shepherd, C. L. & Kulhanek, D. K. (2016). Eocene nannofossil biostratigraphy of the mid-Waipara River section, Canterbury Basin, New Zealand. Journal of Nannoplankton Research. 36(1): 33-59. gs O

Wei, W., Liu, L. & Bukry, D. (1993). Reappraisal of three calcareous nannofossil species: Coccolithus crassus, Toweius magnicrassus, and Toweius callosus. Journal of Micropalaeontology. 12(1): 91-98. gs