Catalog - Braunella

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Braunella

Citation: Braunella Georgescu 2007

Type age (chronostrat): Late Campanian-Maastrichtian, from Radotruncana calcarata Biozone to and throughout Pseudoguembelina hariaensis Biozone.

Type locality: United States (Texas, Arkansas, southern California), Mexico, Caribbean (Puerto Rico, Cuba, Trinidad, Yucatan Shelf), Atlantic Ocean (Or- phan Basin, Grand Banks, Blake Nose Plateau, Rio Grande Rise, Sao Paolo Plateau), Tethyan Realm (Israel), Pacific Ocean (Shatsky Rise), and Europe (Italy, Denmark)

Diagnosis.– Test biserial, with subspherical chambers throughout. Chambers increase more or less regularly in size as added. Sutures distinct and depressed. Main aperture in the shape of a low- to medium-high arch, situated at the base of the last-formed chamber. Test ornamentation irregularly reticulate, at least in the earlier portion; chambers sometimes costate.
Description.– Test robust, biserial throughout. Chambers are subspherical, with the younger distinctly overlapping the previously formed ones. Chambers increase more or less regularly in size as added, resulting in highly variable shape of the test in lateral view. Chamber proliferation may occur occasionally in rare specimens. Sutures are distinct, depressed, and straight to slightly oblique to the axis of growth. Main aperture has the shape of a low to medium high arch, situated at the base of the last formed chamber of the test. It is bordered by two lateral, imperforate, rod-like rims, which are or are not attached to the penultimate chamber, and a wide imperforate band in the central part. Additional apertures can be developed along the zigzag suture if the rod-like rims are suspended. Test ornamentation is irregularly reticulate throughout. Costate ornamentation was observed on the last-formed chambers of some specimens. The test wall is calcareous, hyaline, finely perforate, the pores being situated in the spaces de- fined by the irregular reticulate network, or between the robust costae.

The genus named after Professor Willi K. Braun (University of Saskatchewan) in appreciation for his dedication to micropaleontological-biostratigraphical studies of the Paleozoic and Mesozoic microfaunas of Western and Arctic Canada.

Remarks.– The distinct, irregular reticulation of the test separates Braunella nov. gen. of the coeval Heterohelix s.l. species, the latter having dominant costate ornamentation, and from Pseudotextularia, which has pronounced, coarse costae. Occasional chamber proliferation in Braunella nov. gen. is developed between two rows of diverging chambers, whereas, by contrast, in Pseudotextularia- Racemiguembelina lineage the chambers of the proliferating stage are added in two planes resulting in a cone-shaped test. Pseudoguembelina Brönnimann & Brown presents secondary apertures along the zigzag suture as a result of chamber prolongation. By contrast, the supplementary apertures in Braunella are the result of the development of the periapertural structures. The ornamentation is different in Pseudoguembelina and Braunella, the former being completely costate and the latter presenting irregular reticulate ornamentation.

Phylogenetic relationships.– Braunella nov. gen. apparently derives from costate Heterohelix species of the H. striata group (Fig. 2). This assumption is supported by (i) occasional presence of last-formed costate chambers in some specimens of the new genus, (ii) identical periapertural structures at Heterohelix striata and Braunella punctulata and (iii) occurrence of transitional test ornamentation between the costate and presumed H. striata ancestor and the irregularly reticulate, Braunella punctulata descendant.

References:

Georgescu, M. D. (2007b). Taxonomic re-evaluation of the Late Cretaceous serial planktonic foraminifer Gümbelina punctulata Cushman, 1938 and related species. Revista Española de Micropaleontología. 39: 1-14. gs

CATALOG OF ORIGINAL DESCRIPTIONS: Braunella Georgescu 2007

Braunella

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