Catalog - Heterohelix fayose

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Heterohelix fayose

Citation: Heterohelix fayose Petters 1983

Type specimens: holotype (U.S.N.M. 328698) and paratype (U.S.N.M. 328699)

Type sample (& lithostrat): Nkalagu Formation

Type age (chronostrat): Lower Turonian

Type locality: Roadcut on the Enugu-Port Harcourt expressway, 47 km from the old Umuahia road-expressway junction towards Enugu; nigeria

Type repository: Washington; USNM

Test small, biserial, narrow, elongate and gradually flaring. Periphery narrow and rounded; lobulate outline. Five to seven pairs of low, interlocking chambers, except the last two pairs which are reniform and elongate in the direction of growth. Sutures slightly oblique, wide and depressed. Aperture a broad arch, almost reaching the middle of the apertural face, bordered by a short lip. Wall calcareous, smooth to finely costate.

Length of holotype 0.26 mm, maximum width 0.12 mm.

After Professor E. A. Fayose, first Nigerian micropaleontologist.

Heterohelix pulchra EICHER and WORSTELL, 1970, p. 296, pl. 8, figs. 9-10.

Remarks. Variation among H. fayose affects the number of chambers, the degree of reniform chamber development, test compression, and wall ornamentation. Heterohelix fayose is similar to H. pulchra (Brotzen), but the latter has a wider test, more pronounced reniform and interlocking chambers, and a smooth wall. The initial part of the test of Lunatriella spinifera is very similar to H. fayose, and gradational forms occur between both species. Heterohelix fayose and the initial part of the test of L. spinifera show strong similarity to H. moremani and suggest descent from the latter with H. fayose as the intermediate stage. This lineage has a stratigraphic basis in view of the fact that Heterohelix moremani ranges from Cenomanian to Turonian in North America (Pessagno, 1967; Petters, 1977), while H. fayose and L. spinifera are early Turonian with H. fayose starting lower at the type locality than L. spinifera.

The suggested phylogenetic status of H. fayose modifies that of Eicher and Worstell (1970). Eicher and Worstell proposed the evolution of L. spinifera from H. pulchra. However, H. pulchra has a Campanian-Maastrichtian range in the U.S. Gulf Coast (Pessagno, 1967), a Santonian-early Maastrichtian range in New Jersey (Petters, 1977), and a Coniacian-Maastrichtian range in Europe (Peryt, 1980). In view of the unusually low occurrence of H. pulchra in the U.S. midcontinent (early Turonian), Eicher and Worstell (1970, p. 296) remarked that the specimens they identified as H. pulchra "may belong to a different lineage." Indeed, this is the case, and these forms are here included in H. fayose and placed in the H. moremani-H. fayose-L. spinifera lineage.

References:

Petters, S. W. (1983). Gulf of Guinea planktonic foraminiferal biochronology and geological history of the South Atlantic. Journal of Foraminiferal Research. 13(1): 32-59. gs

CATALOG OF ORIGINAL DESCRIPTIONS: Heterohelix fayose Petters 1983

Heterohelix fayose

References:

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