Nannotax3 - ntax_cenozoic - Hornibrookina weimerae Nannotax3 - ntax_cenozoic - Hornibrookina weimerae

Hornibrookina weimerae

Classification: ntax_cenozoic -> Isochrysidales -> Prinsiaceae -> Hornibrookina -> Hornibrookina weimerae
Sister taxa: H. australis, H. elegans, H. indistincta, H. teuriensis ⟩⟨ H. weimerae, H. gracilis, H. sp.


Citation: Hornibrookina weimerae Self-Trail, 2011
taxonomic rank: Species
Taxonomic discussion: I regard assignment of this species to Hornibrookina as uncertain since: (1) The tube and distal shield elemennts appear to be formed from the same crystal units (images Self-Trail et al 2022 pl3 f8 f11 & f12);  (2) the central grill elements appear to be birefringent. In both these respects and in the presence of slits in the distal shield it resembles H. nicolasii and like that species it may be a reticulofenestrid. This would make it the earliest known Reticulofenestra. [my interpretation - JRY 2022]

Distinguishing features:
Parent taxon (Hornibrookina): Elliptical placoliths with bicyclic distal shields with raised tube cycle and central area grill formed from robust bars.
This taxon: Very small (2-3µm), narrowly elliptical, bars platy and thickened centrally giving appearance in LM of a longitudinal bar.

Farinacci & Howe catalog pages: H. weimerae *


Hornibrookina weimerae most closely resembles H. teuriensis in being elongate oval with a relatively bright distal shield. However, it is much smaller, in both length and diameter, with a narrower central area (Self-Trail 2011).

In LM the central area apears to be filled by a central longitudinal bar, and individual transverse laths are impossible to discern. The proximal shield is relatively bright in XPL.
In SEM it appears that there is no longitudunal bar, but rather that the bars from either side are thickened, the bars are lath-like and butt against each other rather being separated by slits.

2-0-2.6µm long, 1.2-1.7µm wide

Search data:
LITHS: placolith, elliptical, CA: ca_disjunct, grill,
CSPH: equant, monomorphic, CROSS-POLARS: rim-bicyclic, V-prominent, R-prominent,
Lith size: 2->3µm;
The morphological data given here can be used on the advanced search page. See also these notes

Geological Range:
Last occurrence (top): within NP11 zone (53.70-54.17Ma, top in Ypresian stage). Data source: Self-Trail et al. 2022
First occurrence (base): within NP4 zone (61.51-63.25Ma, base in Danian stage). Data source: Self-Trail et al. 2022

Plot of occurrence data:


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., 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


Hornibrookina weimerae compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 25-7-2024

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Short stable page link: Go to to create a permanent copy of this page - citation notes

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