Catalog - Chiloguembelina praecursor

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Chiloguembelina praecursor

Citation: Chiloguembelina praecursor Peryt 1980

Type specimens: pl. 3, figs. 1, 3, 6, 7: Fig. 6 = holotype; figs 1, 3, 7 = three paratypes.: holotype (fig. 6), no. FXXIII/36; and 3 paratypes (figs. 1, 3, 7), nos. FXXIII 34, 35, 37, respectively

Type sample (& lithostrat): "Opoka" [siliceous limestone] in the top 2 beds of marls

Type age (chronostrat): Upper Cretaceous. upper Maastrichtian, horizon "x,'' Guembelitria cretacea Zone.

Type locality: 500 m. wide quarry at Kazimierz, on the east bank of the Vistula River in central Poland.

Type repository: Warsaw; Institute of Paleobiology of the Polish Academy of Sciences, Warsaw, Poland;

Diagnosis. - Test biserial, consisting of 6-8 pairs of chambers, in initial portion entire, in later portion indented: chambers subglobular, striate, primary aperture eccentric in position, bordered by two parallel lateral Fanges.

Description. - Test small, biserial, tapering, sometimes with curved initial part of test; in initial portion periphery entire, in later portion indented: first chambers subrectangular, in adult stage subglobular; sutures flush in initial portion, depressed in later portion; wall distinctly ornamented by longitudinal discontinuous striae: primary aperture eccentric, bordered by two parallel lateral flanges

Dimensions (in mm.). - (Length) (Width) (Thickness) Holotype (fig. 6) 0.33 0.18 0.10 Paratype (fig. 7) 0.21 0.14 0.08

Variability. - Marked in shape of test - from straight to slightly twisted, in number of chambers, intensity of ornamentation, shape and position of ultimate chamber and in postition of aperture.

Remarks. - Loeblich and Tappan (1956. Washington Acad. Sci., Jour., vol. 46, no. 11, p. 340) erected the genus Chiloguembelina so as to include some Tertiary species that were previously referred to Guembelina. Chiloguembelina is distinguished from Heterohelix mainly in the presence of neck-like apertural extensions, the tendency to develop a twisted test and the asymmetrical aperture. The oldest occurrences of this genus were previously reported from the Lowermost Paleocene in association with Chiloguembelina crinita (Giaessner) [ Cuembelina crinita, 1937] and Chiloguemhelina midwayensis (Cushman) [Cuembelina midwayensis, 1946]. C. praecursor Peryt is the transitional species between the genera Heterohelix and Chiloguembelina. Possessing ornamentation of Upper Cretaceous Heterohelix type it has an asymmetrically placed primary aperture and slightly twisted test. As the presence of an asymmetrically placed aperture is one of the diagnostic features of the genus Chiloguembelina, this species was included in that genus. C. praecursor Peryt found in the Upper Campanian and Upper Maastrictian deposits of the Vistula River profile, is the oldest known representative of Chiloguembelina. C. praecursor Peryt is similar to C. crinita (Giaessner) and C. midwayensis (Cushman) in test size but differs in possessing discontinuous longitudinal striae instead of hispid surface. It differs from C. crinita in having chambers increasing less sharply in size as added and in having weaker developed lateral tlanges. C. praecursor Peryt differs from C. midwaysensis in having chambers subglobular to globular in shape and possessing less strongly developed lateral flanges.

Also found at Wesolowka. Jarentowskie Pole, and Lucimia, also in the Vistula River valley of central Poland.

Ranges down through lower Maastrichtian and upper Campanian, Rugoglobigerina pennyi and Globigerinelloides multispinus zones, to lower Campanian Globotruncana arca zone.

References:

Peryt, D. (1980). Planktic foraminifera zonation of the Upper Cretaceous in the middle Vistula River valley, Poland. Palaeontologia Polonica. 41: 1-123. gs

CATALOG OF ORIGINAL DESCRIPTIONS: Chiloguembelina praecursor Peryt 1980

Chiloguembelina praecursor

References:

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