Catalog - Rugoglobigerina milamensis

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Rugoglobigerina milamensis

Citation: Rugoglobigerina milamensis Smith&Pessagno 1973

Type specimens: Plate 24, figures 4-7; 170544

Type sample (& lithostrat): TX9AD, dark gray, conchoidal fracturing, calcareous mudstone, about 8.5 feet above base of exposure.

Type age (chronostrat): Maastrichtian

Type locality: Bluff along the southern bank of Walkers Creek, 5.6 miles N. 21 degrees East of Cameron, Milam County, TX, USA.

Type repository: Washington; USNM

Test trochospiral, strongly spiroconvex, early whorls offset in a higher plane than ultimate whorl; peripheral margin subcircular, lobate; 5-6 chambers in the final whorl spherical to subspherical, in apertural and abapertural views slightly elongate axially, ultimate chamber slightly offset umbilically; initial chambers on spiral side increasing rapidly in size as added, chambers of final whorl increasing only slightly in size; sutures radial, curved, strongly, depressed; chambers of ultimate whorl heavily rugose, rugosities or costellae closely spaced, aligned in a meridional pattern, ultimate chamber generally more finely rugose; wall finely perforate; umbilicus large, subrectangular, deep; primary aperture interiomarginal, umbilical; spiral system of tegilla with intralaminal and infralaminal accessory apertures poorly preserved in specimens examined.

Holotype measures 435 µm in length, 415 µm in width, and 340 µm in maximum thickness.

1962. Rugoglobigerina rugosa (Plummer). BERGGREN, pp. 71-75, pI. 11, figs. 3a-c, 5a-b; not figs. la-b, 2, 4a-c; not text-fig. 8.
1963. Globotruncana (Rugoglobigerina) rugosa (Plummer), VAN HINTE, p. 92, pI. II, figs, 2a-c; 3a-c; not figs. la-c.
1964. Rugoglobigerina rugosa (Plummer). OLSSON, p. 173, pI. 7, figs. 3a-c, 4a-c; not figs. 2a-e, 5a-e.
1966. Rugoglobigerina rotundata Bronnimann. DOUGLAS and SUTER, p. 116, pl. 1, figs. 5a-c; not figs. 2a-c, 6a-c.

Remarks.-Rugoglobigerina milamensis, n. sp., has been previously figured (see synonymy) as R. rugosa (Plummer). It differs from the latter species in being much more strongly trochospiral, and in having a slight rather than rapid increase in chamber size. Rugoglobigerina milamensis differs from R. rotundata Bronnimann in being more trochospiral, in having chambers which, in apertural view, are not strongly elongate axially, in having coarse and well developed meridional rugosities, and in having a large rather than small umbilicus. It differs from R. trading housensis Pessagno (= ? R. pilula Belford) in having strongly developed meridional rugosities or costellae on all chambers of the ultimate whorl, and in having a much larger umbilicus.

Range.-G. contusa-stuartiformis Assemblage Zone, G. gansseri Subzone, lower part of G. aegyptiaca Zonule, to upper part of A. mayaroensis Subzone (insofar known).

Occurrence.-Rugoglobigerina milamensis, n. sp., has been figured previously as R. rugosa from the Maestrichtian of Denmark (Berggren, 1962); Pemberger Folge (Maestrichtian) of Austria (van Hinte, 1963); and the Redbank and Mt. Laurel Formations (Maestrichtian) of New Jersey (Olsson, 1964). Douglas and Sliter (1966) figured this form as R. rotundata Bronnimann from the Marsh Creek Formation of Contra Costa County, California.

During the present investigation, this species was observed in the Corsicana Formation (middle Maestrichtian, G. aegyptiaca Zonule) along Onion Creek, Travis County, Texas; Corsicana Formation (middle Maestrichtian, R. fructicosa Zonule) of North Central Texas; Papagallos Shale (middle Maestrichtian, R. fructicosa Zonule) of Mexico (see Appendix, Pessagno sample MXI74); Mendez Shale (late Maestrichtian, A. mayaroensis Subzone) of Mexico (Pessagno sample MX78); and the Guayaguay are Formation (late Maestrichtian, A. mayaroensis Subzone) of Trinidad.

References:

Smith, C. C. & Pessagno, E. A. (1973). 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. Cushman Foundation for Foraminiferal Research, Special Publication. 12: 1-67. gs O

CATALOG OF ORIGINAL DESCRIPTIONS: Rugoglobigerina milamensis Smith&Pessagno 1973

Rugoglobigerina milamensis

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