Nannotax3 - ntax_cenozoic

Citation: Prinsiaceae Hay & Mohler, 1967 emend. Young & Bown, 1997

Taxonomic discussion: Toweius coccoliths are larger than Prinsius, with wider central areas and therefore more clearly visible central area nets in LM. Similarly, Futyania coccoliths are similar to Prinsius but have distally elevated tube elements.
Neobiscutum and Hornibrookina are conventionally placed in the Prinsiaceae, but may be unrelated.

Distinguishing features:
Parent taxon (Isochrysidales): 2N: Mostly placolith heterococcoliths with R-unit dominant. Non-motile
N: non-calcifying, motile, with vestigial haptonema.
This taxon: Placoliths with R-units forming the lower layer of proximal shield, inner tube and middle tube; V-units forming an upper layer to the proximal shield, outermost tube and the distal shield. In LM they display a dark outer cycle and brighter inner cycle. Central-area structures are conjunct, formed from the R-units.

Original description: Diagnosis.- Oval, subcircular or circular placoliths; interference figure between crossed polarizers is dextrogyre in distal view.

Typically small to medium sized placoliths with R-units forming the proximal shield-element and two tube-elements, and V-units forming an upper layer to the proximal shield, an outermost tube and the distal shield. In LM they display a dark outer cycle and brighter inner cycle. Central-area structures are conjunct, being formed from either the central-area elements or the inner tube-elements of the proximal shield.

Toweius gave rise to Reticulofenestra by loss of the V-units - the middle tube cycle of Prinsiaceae forms the outer tube of reticulofenestrids and extends to form the distal shield - see Gallagher (1989) and Young (1989). The similarity of the structures are much clearer in proximal view than distal view. There is a clear evolutionary lineage from Praeprinsius to Prinsius to Toweius, with i>Futyania a side branch (Romein 1979, Bown et al. 2023).

Geological Range:
Last occurrence (top): at top of NP15 zone (100% up, 42.9Ma, in Lutetian stage). Data source: Total of ranges of the species in this database
First occurrence (base): within CC26 zone (66.04-67.82Ma, base in Maastrichtian stage). Data source: Total of ranges of species in this database

References:

Gallagher, L. T. (1989). Reticulofenestra : A critical review of taxonomy, structure and evolution. In, Crux, J. A. & van Heck, S. E. (eds) Nannofossils and their applications: Proceedings of the 2nd INA Conference, London 1987. British Micropalaeontological Society Publication Series . 41-75. gs O

Hay, W. W. & Mohler, H. P. (1967). Calcareous nannoplankton from Early Tertiary rocks at Point Labau, France and Paleocene-Early Eocene correlations. Journal of Paleontology. 41(6): 1505-1541. 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

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

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

Young, J. R. (1989). Observations on heterococcolith rim structure and its relationship to developmental processes. In, Crux, J. A. & van Heck, S. E. (eds) Nannofossils and their applications: Proceedings of the 2nd INA Conference, London 1987. British Micropalaeontological Society Publication Series . 1-20. gs

Daughter taxa (time control age-window is: 0-800Ma)		Granddaughter taxa
	typical Prinsiaceae
	Futyania Very small (1-2.5 µm) circular to elliptical; central area narrow, tube-elements extended distally to form an elevated flower-like structure.	Futyania petalosa Futyania sp.
	Praeprinsius Very small to small (1-4 µm), circular to sub-circular, coccospheres with numerous coccoliths	Praeprinsius vegrandis Praeprinsius tenuiculus
	Prinsius Small to medium size (3-6 µm), elliptical, central areas narrow, closed or with slit-like opening	Prinsius dimorphosus Prinsius martinii Prinsius bisulcus Prinsius sp.
	Toweius Typically medium-sized.(5-8 µm), elliptical to circular, central areas typically with a conjunct net and/or bars.	Toweius oztunalii Toweius occultatus Toweius eminens Toweius tovae Toweius serotinus Toweius pertusus Toweius reticulum Toweius selandianus Toweius rotundus Toweius patellus Toweius callosus Toweius magnicrassus Toweius brusselensis Toweius gammation Toweius sp.
	conventionally placed in the Prinsiaceae
	Neobiscutum Very small to small placoliths with closed or narrow central areas. Shields are dark in XPL with bright tube cycle.	Neobiscutum parvulum Neobiscutum romeinii Neobiscutum sp.
	Hornibrookina Elliptical placoliths with bicyclic distal shields with raised tube cycle and central area grill formed from robust bars.	Hornibrookina australis Hornibrookina elegans Hornibrookina indistincta Hornibrookina teuriensis Hornibrookina weimerae Hornibrookina gracilis Hornibrookina sp.