Catalog - Globotruncana stephensoni Catalog - Globotruncana stephensoni

CATALOG OF ORIGINAL DESCRIPTIONS: Globotruncana stephensoni Pessagno 1967

This page provides data from the catalog of type descriptions. The catalog is sorted alphabetically. Use the current identification link to go back to the main database.


Higher levels: pf_cat -> G -> Globotruncana -> Globotruncana stephensoni
Other pages this level: << < G. riojai, G. roddai, G. rosetta insignis, G. rosetta pettersi, G. rugosa, G. rugosa subrugosa, G. sahakianae, G. samuriensis, G. schneegansi, G. semsalensis, G. sharawnaensis, G. sigmoconcavata, G. smithi, G. stephani, G. stephani turbinata, G. stephensoni, G. stuarti parva, G. sudrensis, G. sudrensis parallela, G. tarfayaensis, G. thalmanni thalmanni, G. ticinensis, G. torensis, G. tricarinata colombiana, G. tricarinata desioi, G. undulata, G. verrucosa, G. vridhachalensis, G. walfischensis, G. wiedenmayeri, G. wiedenmayeri magdalenaensis> >>

Globotruncana stephensoni

Citation: Globotruncana stephensoni Pessagno 1967
Taxonomic rank: species
Type specimens: Plate 69, figures 1-7; Plate 96, figures 5, 6; 689269
Type sample (& lithostrat): Upper Taylor Marl
Type locality: From sample TX 291-B, collected from a ditch crossing Sate Route 73, 2.4 miles east of the intersection of Route 73 with Farm Road 737, Prairie Hill, Limestone County, TX
Type repository: Washington; USNM

Linked specimens: USNM-689269 USNM-689270

Current identification/main database link: Globotruncana orientalis El Naggar 1966


Original Description

Trochospiral, spiroconvex; periphery sharply angled with narrow double keel merging to form a single keel in the last whorl; rare specimens single-keeled entirely in final whorl, but when sectioned showing double keel in preceding whorl; double keel when present, strongly reflected umbilically. Test having about three whorls of chambers which slowly expand in size; 6-7 chambers in the last whorl. Chambers spirally, typically trapezoidal to subtrapezoidal, but often petaloid, cresent-shaped, or subtriangular, separated by straight to slightly curved, raised, often beaded sutures. Chambers individually smoothed surfaced, containing few if any rugosities. Umbilicus deep and wide; surrounded by umbilical shoulder which may or may not be beaded; umbilicus covered by spiral system of tegilla having intralaminal and infralaminal accessory apertures. Primary aperture interiomarginal, umbilical in position. Outer wall radial hyaline, perforate except for keels. Keels when single predominantly radial hyaline, imperforate; when double in part radial hyaline, imperforate, and ultragranular hyaline, imperforate; umbilical rim of double keel weak, entirely ultragranular hyaline, imperforate; spiral rim with radial hyaline, imperforate base which is strengthened by accretion of ultragranular hyaline outer portion. Septal walls and tegilla microgranular hyaline, finely perforate.

Etymology:
named in honor of the late L. W. Stephenson in recognition of his great contributions to the study of the Cretaceous stratigraphy of the Atlantic and Gulf Coastal Plains

Extra details from original publication
Remarks: G. stephnsoni Pessagno, n. sp. is closely related phylogenetically to G. arca (Cushman). Ephehic individuals of G. stephensoni n. sp. differ from those of G. arca having approximately the same diameter by (1) possessing angled peripheries; (2) narrow double keels which merge to form a single keel in the last whorl; and (3) by usually having more trapezoidally shaped chambers. Both species possess double keels which are strongly reflected umbilically and have similar structure (TYPE 1; Text-figure 40).
G. stephensoni, n. sp. may be perfectly homeomorphic externally for either high-spired forms of G. stuarti (de Lapparent) s.s. or for G. conica White and can only be separated in thin-section from these latter species. Most Campanian and Early Maestrichtian occurrences of G. conica and G. stuarti (de Lapparent) s.s. most likely represent occurrences of G. stephensoni, n. sp. For example, Pessagno (1960, p. 91, chart 2: 1962. p. 355. chart 1) noted G. conica in Puerto Rican strata of Late Campanian and Early Maestrichtian age. The sectioned specimen figured as G. conica White by Pessagno (1962, text-figure 1, p. 362) resembled G. conica externally. It posessed subtrapezoidal chambers spirally and showed a spiroconvex test. However, it also showed a narrow double keel in the posterior portion of the last whorl and in the preceding whorl.

References:

Pessagno, E. A. (1967). Upper Cretaceous planktonic foraminifera from the western Gulf Coastal Plain. Palaeontographica Americana. 5: 245-445. gs O


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Globotruncana stephensoni compiled by the pforams@mikrotax project team viewed: 11-2-2025

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