Catalog - Planoheterohelix postmoremani

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Other pages this level: P. postmoremani, P. praenuttalli

Planoheterohelix postmoremani

Citation: Planoheterohelix postmoremani Georgescu & Huber 2009

Type specimens: Pl. 5, figs. 1–11, fig. 2: 2; 534393

Type sample (& lithostrat): DSDP 463–35–1, 17–19 cm.

Type age (chronostrat): Lower Turonian (H. helvetica Biozone)

Type locality: DSDP Leg 62, Site 463, equatorial Pacific (Mid-Pacific Mountains). 21 21'N, 174 40'E.

Type repository: Washington; USNM

Test is biserial throughout and consists of 11 to 15 chambers. Small proloculus (8.2-14.3 microns) is followed by slightly larger second chamber. Chambers increase gradually in size as added. Earlier chambers are subglobular, those of adult stage are reniform and oblique to the test axis of growth. Sutures are distinct, depressed, and oblique. Tests are symmetrical in edge view, with broadly rounded periphery. Aperture is medium to high arch at base of lastformed chamber; it is bordered by two symmetrically developed periapertural flanges . Chamber surface is ornamented with closely spaced costae, each of them consisting of series of aligned pustules, resulting in a granular appearance. Test wall is calcitic, hyaline, microperforate; pore diameter ranges 0.5-0.9 microns.

Dimensions of holotype. L 5 0.335 mm; W 5 0.175 mm; W/L 5 0.522; t 5 0.103 mm; t/L5 0.307
Size range: L 5 0.222–0.351 mm; W 5 0.128–0.181 mm; W/L 5 0.511–0.577; t 5 0.096–0.110 mm; t/L 5 0.307– 0.432.

The Latin prefix post (= after) is added to the pre-existing species name moremani to emphasize their succession of the two species in the evolutionary sequence

Heterohelix moremani (Cushman) in Nederbragt, 1991, p. 344, pl. 3, fig. 2 only (upper Cenomanian, Tunisia, northern Africa).
Heterohelix moremani (Cushman) in Georgescu, 1995, p. 95, pl. 1, fig. 13 only (lower Turonian, western Black Sea, Romanian offshore).
Heterohelix moremani (Cushman) in Nederbragt and others, 1998, pl. 1, fig. 6 only (upper Cenomanian, Tunisia, northern Africa).
Heterohelix moremani (Cushman) in Wilson and others, 2002, fig. 1:3 (Turonian, Demerara Rise, western North Atlantic Ocean).
Heterohelix moremani (Cushman) in Bak and others, 2005, fig. 5A (upper Cenomanian–lower Turonian, Pieniny Klippen Belt, southern Poland).

Remarks. Planoheterohelix postmoremani differs from its ancestor P. moremani by having fine longitudinal costae on the test surface; this primitive ornamentation consists of rows of unmerged pustules, a feature characteristic of costate Planoheterohelix species. It differs from Protoheterohelix obscura by having symmetrical periapertural structures and a costate surface.

Stratigraphic range. Upper Cenomanian (171B–1050C– 21–2, 99–102 cm) to Coniacian (10–95–16–5, 100.5– 102 cm), from the upper part of Rotalipora cushmani Biozone to Dicarinella concavata Biozone (Tables 1–3).

Geographic distribution. Western North Atlantic Ocean (Blake Plateau, Demerara Rise), equatorial Pacific Ocean (Mid-Pacific Mountains), Europe (Poland, Romanian western Black Sea offshore), and northern Africa (Tunisia).

References:

Georgescu, M. D. & Huber, B. T. (2009). Early evolution of the Cretaceous serial planktic foraminifera (late Albian-Cenomanian). Journal of Foraminiferal Research. 39: 335-360. gs

CATALOG OF ORIGINAL DESCRIPTIONS: Planoheterohelix postmoremani Georgescu & Huber 2009

Planoheterohelix postmoremani

References:

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