Nannotax3 - ntax_cenozoic - Hornibrookina Nannotax3 - ntax_cenozoic - Hornibrookina


Classification: ntax_cenozoic -> Isochrysidales -> Prinsiaceae -> Hornibrookina
Sister taxa: Futyania, Praeprinsius, Prinsius, Toweius ⟩⟨ Neobiscutum, Hornibrookina

Daughter taxa (time control age-window is: 0-800Ma)Granddaughter taxa
Hornibrookina australis
Medium-sized (4-7µm), narrowly elliptical to lenticular, arched, central area with 7-11 pairs of lateral bars
Hornibrookina australis australis
Hornibrookina australis arca

Hornibrookina elegans
Small (3-5 µm); central area wide; R-units often forming high, flaring, collar around central area

Hornibrookina indistincta
Small (3-5 µm), narrowly elliptical to lenticular. Like H. a arca but smaller and flatter.

Hornibrookina teuriensis
Medium to large (5-10 µm) elliptical; central area with ~10 pairs of lateral bars, and a longitudinal bar, sometimes over-calcified; R units often form ring of nodes around central area
Hornibrookina edwardsii

Possible Hornibrookina
Hornibrookina weimerae
Very small (2-3µm), narrowly elliptical, bars platy and thickened centrally giving appearance in LM of a longitudinal bar.

Hornibrookina gracilis
Small (2-4.5 µm) Toweius-like species

Hornibrookina sp.
Specimens which cannot be assigned to any established species


Citation: Hornibrookina Edwards, 1973
taxonomic rank: Genus
Type species: Hornibrookina teuriensis Edwards, 1973
Taxonomic discussion: Coccoliths may be arched and narrowly elliptical to lenticular. Six species have been described but they are all rather similar and possibly should be considered synonyms.

Three addtional species which have been described in Hornbrookina are not included here:

Distinguishing features:
Parent taxon (Prinsiaceae): 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.
This taxon: Elliptical placoliths with bicyclic distal shields with raised tube cycle and central area grill formed from robust bars.

Farinacci & Howe catalog pages: Hornibrookina *


The distal shield and grill are formed of V-units, the proximal shield and inner tube of R-units - this is clear from LMs and the original description. In some species, notably  H. edwardsii and H. teuriensis the grill elements may thicken to fill the central area. The tube cycle of R-units may extend above the shield as continuous collar (e.g in H. elegans) or as ring of nodes (e.g. in H. teuriensis).
Differentiated from Toweius and Prinsius by
NB This a summary of my observations, primarily form images on this website, they suggest that Hornibrookina should not be included in the Prinsiaceae, but this result has not yet been published [JRY 2022]

Phylogenetic relations

Hornibrookina has long been tentatively placed in the Prinsiaceae (e.g. Perch-Neilsen 1985, Young & Bown 1997) but the coccoliths are atypical. In particular (1) The proximal shield appears to be unicyclic in Hornibrookina whereas in theP rinsicaceae it is bicyclic with an upper/outer cycle of V-units and a lower/inner cycle of R-units (2) The central structure in Hornibrookina appears to be disjunct from the rim whereas it is conjunct with it in the Prinsiaceae. So, this assignment should be re-examined [JRY 2016, updated 2022]

Search data:
LITHS: placolith, elliptical, CA: ca_disjunct, grill,
CSPH: equant, monomorphic,
Lith size: 2->9µm;
The morphological data given here can be used on the advanced search page. See also these notes

Geological Range:
Notes: Abundant in lower Paleocene high latitude settings and conspicuous around the PETM interval.
Last occurrence (top): at top of NP14 zone (100% up, 46.3Ma, in Lutetian stage). Data source: Total of ranges of the species in this database
First occurrence (base): within NP1 zone (65.47-66.04Ma, base in Danian stage). Data source: Total of ranges of species in this database

Plot of occurrence data:


Edwards, A. R. (1973b). Key species of New Zealand calcareous nannofossils. New Zealand Journal of Geology and Geophysics. 16: 68-89. 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 427-555. gs

Self-Trail, J. M., Watkins, D. K., Pospichal, J. J. & Seefelt, E. L. (2022). Evolution and taxonomy of the Paleogene calcareous nannofossil genus Hornibrookina. Micropaleontology. 68(1): 85-113. gs

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


Hornibrookina compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 16-7-2024

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