Catalog - Costellagerina

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Costellagerina

Citation: Costellagerina S. W. Petters, El-Nakhal,&Cifelli 1983

Type species: Rugoglobigerina bulbosa Belford, 1960.

Test low to medium trochospirai; outline sub-circular, ovate, or quadrate; equatorial periphery strongly lobulate; axial periphery broadly rounded; chambers globose; aperture an interiomarginal, low arch, umbilical to slightly extraumbilical, bordered by a porticus; umbilicus open, small tomoderate in size. Wall hyaline, ornamented with pustules and costellae which are meridionally arranged.

The name Costellagerina is derived from 'costellae'

Remarks. - Costellagerina differs from Hedbergella in the meridionally aligned pustules and costellae. According to Banner and Blow (1959) Hedbergella has no costellae. The types of Hedbergella libyea Barr, 9172 in the collection of the U.S. National Museurn are here placed under Costellagerina because they display distinct and meridionally arranged costellae. The middle Cenomanian form H. costellata Saint-Marc, I973, which was described from Lebanon was considered a synonym of H. libyca by McNulty and Barr (1979).

Costellagerina is distinguished from the Campanian-Maastrichtian genus Rugoglobigerina by the absence of umbilical cover plates (tegillae) and imperforate peripheral bands. Because of the absence of tegillae Belford (personal communication) recently removed from Rugoglobigerina western Australian Santonian forms which he previously referred to as R. (Rugoglobigerina) bulbosa Belford, 1960, and R. (R.) pilula, Belford, 1960, while R. (R.) plana Belford, 1960, which lacks a well defined meridional ornamentation was placed under Hedbergela. The occurrence of Costellagerina bulbosa (Belford) and C. pilula (Belford) in the Santonian-early Campanian of California (Douglas, 1969; Douglas and Sliter, 1966), the U.S. Western Interior (Frerichs, 1979; Frerichs and Dring, 1981), the Carpathians (Hanzlikova, I972), and in Nigeria and Tunisia (this study) attests to the cosmopolitan distribution of this genus. The wide latitudinal range of these species, which display a persistent pattern of meridionally aligned costellae, lends no credence to Blow's (1979) argument that this type of ornamentation is ecophenotypic and confined to the low latitudes. Since Rugoglobigerina has a Campanian-Maastrichtian range (Belford, pers. comm.; Hofker, 1961; Pessagno, 1967), and evolved from rugose globotruncanids (Olsson, 1964), meridionally constellate hedbergellid forms in older strata (Bolli, 1959) are here referred to Costellagerina.

Whiteinella Pessagno, 1967, by definition includes sub-globotruncanid forms with a very shallow umbilicus but does not include meridionally costellate forms, hence the New Jersey Coniacian-early Campanian forms which exhibit this characteristic feature and were placed in Whiteinella by Petters (1977) are here included in Costellagerina. Although Archaeoglobigerina Pessagno, 1967, may exhibit weakly aligned pustules (Douglas and Rankin, 1969), the presence of tegillae separates this genus from Costellagerina. Loeblichella Pessagno, 1967, is distinguished from Costellagerina by its spiral sutural supplementary apertures and the absence of meridionally aligned costellae.

Costellagerina is placed in the family Rotaliporidae (emended Pessagno, 1967, op. cit.) because this family includes globigerine forms with an extraumbilical-umbilical aperture, and portici which extend over the aperture. Pessagno ( 1967, op. cit.) considered the Rotaliporidae the basic stock from which most Late Cretaceous planktonic foraminifera evolved. Costellagerina most likely evolved from Hedbergella.

The name Costellagerina is derived from 'costellae' which Banner and Blow ( 1959) defined as 'ridge-like thickenings . . . typically running in a meridional direction to converge at a "pole" at the mid-point of the chamber periphery.' Costellagerina probably acquired its distinctive ornamentation among the Rotaliporidae by a fusion of the pustules, as previously noted by Blow (1979 p. 1366). The wall surface of Costellagerina, like that of Hedbergella has minute, widely spaced pores which are reminiscent of the Early Cretaceous genus Favusella. The narrow, stringy costellae also invite a comparison with the Early Cretaceous form, but there is no tendency whatsoever in Costellagerina for the costellae to form a web-like or cancellate pattern. That the costellae are formed by a fusion of pustules can be seen in pl. I, fig. 15 (Petters, El-Nakhal and Cifelli, 1983, op. cit.) where short ridge segments are composed ofjoined pustules.

What are these topographic expressions that we, following precedent, have loosely referred to as pustules? Almost certainly they are not true pustules as defined by Hemleben (1975) because they do not appear to be extensions of the primary laminated wall. For the same reason, and because they are neither hollowed nor pyramidal in shape, they cannot be referred to the muricae of Blow (1979 p. 400). The pustulose projections of Costellagerina compare most favorably with the spine bases of spinose species. They are composed of thin, tiered crystallites with angular, acicular caps that appear to be essentially the same as the remnants of broken, elongate spines of modern spinose species (pl. I, figs. 15, 16, Petters, EI-Nakhal and Cifelli, 1983; Cifelli, 1982). The costellae, formed by the fusion of these pustulose projections or spine bases, are in good agreement with the ridges of Cenozoic spiny species. The principal difference is that costellae are oriented meridionally, a peculiarly Cretaceous tendency, while ridges of Cenozoic forms are either dispersed irregularly among the pores or are arranged in a geometric honeycomb or cancellate pattern with each honeycomb surrounding a single pore (Cifelli, 1982, foe. cil.). Costellae also tend to be thinner and stringier than ridges; in late stages of calcification the costellae may be overgrown and have a beaded appearance (pl. I, figs. 13, 16, Petters, El-Nakhal and Cifelli, 1983, op. cil.).

References:

Banner, F. T. & Blow, W. H. (1959). The classification and stratigraphical distribution of the Globigerinaceae. Palaeontology. 2(1): 1-27. gs

Blow, W. H. (1979). The Cainozoic Globigerinida: A study of the morphology, taxonomy, evolutionary relationships and stratigraphical distribution of some Globigerinida (mainly Globigerinacea). E. J. Brill, Leiden. 2: 1-1413. gs

Cifelli, R. (1982). Early Occurrences and some Phylogenetic Implications of Spiny, Honeycomb Textured Planktonic Foraminifera. Journal of Foraminiferal Research. 12(2): 105-115. gs

Douglas, R. G. (1969). Upper Cretaceous planktonic foraminifera in northern California. Part 1 - Systematics. Micropaleontology. 15(2): 151-209. gs

Frerichs, W. E. (1979). Planktonic foraminifera from the Sage Breaks Shale, Centennial Valley, Wyoming. Journal of Foraminiferal Research. 9(2): 159-184. gs

Petters, S. W., El-Nakhal, H. A. & Cifelli, R. (1983). Costellagerina, a new late Cretaceous Globigerine foraminiferal genus. Journal of Foraminiferal Research. 13(4): 247-251. gs

CATALOG OF ORIGINAL DESCRIPTIONS: Costellagerina S. W. Petters, El-Nakhal,&Cifelli 1983

Costellagerina

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