Catalog - Racemiguembelina powelli

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Other pages this level: R. pomeroli, R. powelli

Racemiguembelina powelli

Citation: Racemiguembelina powelli Smith&Pessagno 1973

Type specimens: Plate 11, figures 4-6, 7-9, 10-12; holotype - USNM170535

Type age (chronostrat): Maastrichtian

Type locality: Eastern bank of the Brazos River north of Farm Road 413 bridge

Type repository: Washington; USNM

Initial one-half to two-thirds of test biserial, in later stage becoming multiserial due to chamber proliferation, resulting in a conically-shaped test; in lateral view, multiserial portion of test consisting of chambers lying in two or three planes only; top view of test broadly ovate to circular, consisting of from four to eight globular chambers; initial three or four pairs of chambers indistinct; flattened, increasing gradually in size, becoming strongly inflated and increasing rapidly in size in the median portion of the test; terminal chambers large, globular, strongly inflated, increasing slightly, or showing no increase in size as added; sutures initially flush to slightly depressed, becoming curved and deeply depressed; wall coarsely perforate and costate; pores closely spaced, aligned in three to four irregular vertical columns in intercostal areas; costae massive, highly raised, widely spaced, vertically arranged in a discontinuous pattern on chamber surfaces; each terminal chamber possessing a basal, rather wide and highly arched aperture opening into the central portion of the test; apertures covered by ponticuli in well-preserved specimens.

Racemiguembelina powelli Smith and Pessagno, n. sp., is named in honor of Dr. J. Dan Powell in recognition of his contributions toward a better understanding of the Cretaceous stratigraphy and paleontology of the Gulf Coastal Plain.

1938. Pseudotextularia varians Rzehak. CUSHMAN, pp. 21-22, pl. 4, figs. la-b('?); not figs. 2a-b, 3a-b, 4.
1943. Pseudotextularia varians Rzehak. CUSHMAN and TODD, p. 65, pl. 11, fig. 17.
1946. Pseudotextularia varians Rzehak. CUSHMAN, p. 110, pl. 47, figs. 4a-b(?); not figs. 5a-b, 6, 7a-b.
1946. Planoglobulina acervulinoides (Egger). CUSHMAN, p. 111, pl. 47, figs. 15a-b; not figs. 12a-b, 13a-b, 14a-b.
1957. Racemiguembelina fructicosa (Egger). GALLITELLI, pp. 142-143, pl. 32, figs. 14a-b, 15a-b.
1964. Racemiguembelina fructicosa (Egger). LOEBLICH and TAPPAN, p. C656, fig. 525: 8a-b.
1967. Racemiguembelina fructicosa (Egger). PESSAGNO, p. 270, pl. 90, figs. 14-15.
1969. Pseudotextularia elegans (Rzehak). BROWN, pp. 43-54, pl. 2, figs. 4a-b; pl. 3, figs. 2-3(?); text-fig. 14; not text-figs. 9a-b, lOa-b, 13a-c.
1969. Racemiguembelina fructicosa (Egger). PESSAGNO and BROWN, p. 116, pl. 1, figs. 1-4.

Remarks.-Raeemiguembelina powelli Smith and Pessagno, n. sp., differs from R. fructicosa (Egger) (1) by having a well-developed biserial stage comprising one-half or more of the test, (2) by having larger medial and termi nal chambers and more strongly depressed sutures, result ing in a much more strongly lobate test as observed in lateral view (pl. 11, figs. 4,7,10), (3) by having fewer chambers in the terminal multiserial portion of the test (four to twelve as opposed to eighteen or more in R. fructicosa) which lie in only two or three planes as observed in lateral view (pl. 11, figs, 4, 7, 10), and (4) by having more massive and widely-spaced costae.

Existing morphologic and stratigraphic evidence suggests that Racemiguembelina powelli, n. sp., represents the earliest stage of Racemiguembelina development in the Pseudotextularia deformis-Racemiguembelina fructicosa bioseries. There is little doubt that R. powelli, n. sp., evolved from Pseudotextularia deformis (Kikoine). Transitional forms have been encountered (pl. 11, figs. 1-3) which possess a constricted ultimate chamber and a basal, sup plementary aperture as observed in abapertural view (pl. 11, fig. 3). In both chamber shape and arrangement, as well as pore pattern and costal ornamentation, the transitional forms are otherwise similar to Pseudotextularia deformis.

Racemiguembelina powelli, n. sp., is a morphologically distinct species which has been found to have important stratigraphic value in the middle Maestrichtian strata of Texas, It is the only species of Racemiguembelina known to occur in the Corsicana Formation (G. aegyptiaca Zon ule) of Travis County, Texas (see text fig. 4). Detailed examination has shown that R. powelli, n. sp., gave rise through transitional forms to R. fructicosa, one of several species which distinguish the assemblage of the Racemiguembelina fructicosa Zonule (see text fig. 3).

Range.-G. contusa-stuartiformis Assemblage Zone, G. gansseri Subzone, G. aegyptiaca Zonule, to the upper part of the A. mayaroensis Subzone.

Occurrence. Racemiguembelina powelli, n. sp., has been previously figured under a variety of names from the late Maestrichtian of Cuba (Seiglie, 1959); Mendez Shale of Mexico (Cushman, 1938; 1946); Corsicana and Kemp Formations of Texas (Cushman and Todd, 1943; Galli telli, 1957; Loeblich and Tappan, 1964; Pessagno, 1967; Brown, 1969; Pessagno and Brown, 1969); and the Prairie Bluff Chalk of Alabama (Cushman, 1946). It has also been recorded from the late Maestrichtian of Cuba (Voorwijk, 1937, p. 194); Galicia Bank, a seamount off the western coast of Spain (FunnelI, et a!., 1969, p. 26); Egypt (Said and Kerdany, 1961, p. 334); and from a mixed Upper Cretaceous to Recent fauna from a flat topped seamount west of Hawaii (Hamilton, 1953, p. 235).

During the present investigation, Racemiguembelina powelli, n. sp., has been observed in the middle Maestrichtian (G. aegyptiaca Zonule) Corsicana Formation of Travis County, Texas; middle Maestrichtian (R. fructicosa Zonule) PapagalIos Shale of Mexico, Escondido Formation of West Texas, Corsicana Formation of North Central Texas, and Arkadelphia Marl of Arkansas; and the late Maestrichtian (A. mayaroensis Subzone) Mendez Shale of Mexico. The distribution and abundance of R. powelli in the Corsicana Formation of Texas is shown in text figs. 4-8.

References:

Smith, C. C. & Pessagno, E. A. (1973). Planktonic foraminifera and stratigraphy of the Corsicana formation (Maestrichtian) North-central Texas. Cushman Foundation for Foraminiferal Research, Special Publication. 12: 1-67. gs O

CATALOG OF ORIGINAL DESCRIPTIONS: Racemiguembelina powelli Smith&Pessagno 1973

Racemiguembelina powelli

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