Nannotax3 - ntax_cenozoic - Hornibrookina elegans Nannotax3 - ntax_cenozoic - Hornibrookina elegans

Hornibrookina elegans


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

Taxonomy:

Citation: Hornibrookina elegans (Perch-Nielsen 1981) Self-Trail et al. 2022
taxonomic rank: species
Basionym: Nodosella? elegans Perch-Nielsen 1981
Synonyms: According to Self-Trail et al. 2022 this species has frequently been reported as H. edwardsii
Taxonomic discussion: In the original description, Perch-Nielsen (1981) placed H. elegans questionably into the Jurassic genus Nodosella, primarily “due to the lack of a more likely genus” in which to place her specimens. She discounted placement in the genus Hornibrookina because she felt that H. elegans n. comb. lacked a well-developed distal shield. However, examination of specimens from the Solomons Island core (Pl. 2, figs. 1–3) clearly shows the presence of a distal shield and thus placement in the genus Hornibrookina is warranted. [Self-Trail et al. 2022].
Transfer of this species to Hornibrookina was also proposed by Young (2023).

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

Farinacci & Howe catalog pages: N. elegans *


Morphology:

This small to medium-sized form has 18-31 horizontal/transverse laths and a longitudinal bar in the central area. The most remarkable feature of H. elegans is the extreme exaggeration of the oval wall of steeply dipping, imbricate laths that is mentioned in the original description of the genus (Edwards 1973). In most species of Hornibrookina, this oval can be seen as a thin collar that abuts against the blocky elements of the central area. In H. elegans, the elements of the collar extend vertically upward significantly above the distal shield, forming a large flange. In many cases, the flange is partially broken, which results in a relatively thin outer rim in the LM when compared to unbroken specimens. In the LM, this flange, which is very bright and thick when unbroken, clearly differentiates H. elegans from any other species of Hornibrookina. [Self-Trail et al. 2022]


Ecology & Biogeography

Possibly restricted to the Atlantic and adjacent shelf-sea according to Self-Trail et al. 2022

Search data:
Lith size: 3.5->5.3µm; Segments: 19->25;
Data source notes: Self-Trail et al. 2022
The morphological data given here can be used on the advanced search page. See also these notes

Geological Range:
Notes:

Early Paleocene, Zones NP1–3.


Last occurrence (top): within NP3 zone (63.25-64.81Ma, top in Danian stage). Data source: Self-Trail et al. 2022
First occurrence (base): within NP1 zone (65.47-66.04Ma, base in Danian stage). Data source: Self-Trail et al. 2022

Plot of occurrence data:

References:

Perch-Nielsen, K. (1981). New Maastrichtian and Paleocene calcareous nannofossils from Africa, Denmark, and USA and the Atlantic, and some Paleocene lineages. Eclogae Geologicae Helvetiae. 74(3): 831-863. gs O

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

Varol, O. (1998). Palaeogene. In, Bown, P. R. (ed.) Calcareous Nannofossil Biostratigraphy. British Micropalaeontological Society Publication Series . 200-224. gs

Young, J. R. (2023). Some proposed changes to the systematics of Cenozoic and Mesozoic nannoplankton. Journal of Nannoplankton Research. 41(1): 15-25. gs


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Hornibrookina elegans compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 22-2-2024

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