Citation: Globigerina prasaepis Blow 1969Rank: speciesType specimens: PPM P 49618Type age (chronostrat): Lower to middle Oligocene, Zone P. 19 (= Globigerina sellii
Pseudohastigerina barbadoensis Concurrent-range zone), lower Lukuledi Formation. Ranges from middle to upper parts of Zone P. 18 (Lower Oligocene) to near the Zone N. 2/ Zone N. 3 boundary (Upper Oligocene).Type locality: Holotype (fig. 13) from Kitunda Cliff (sample FCRM 1965), Lindi area, Tanzania; one paratype (fig. 7) from the east bank of the Madingura River (sample FCRM 1922), of the same area; and three paratypes (figs. 3-6) from the lower part of the Cipero Formation (sample WHB.195), north of San Fernando, Trinidad, West Indies.Type repository: London, UK; NHM
Original Description The large globose test consists of about 14 chambers arranged in a low trochospire with 3 1/6 chambers in the final whorl. The chambers of the final whorl are moderately inflated, subspherical but fairly closely appressed, especially the last chamber. The umbilicus is deep, open and rectangular in outline. The aperture of the final chamber is an elongate, low arch extending from the umbilical shoulders of the two opposing earlier chambers; the confines of the aperture extend well beyond the umbilicus. The aperture is bordered by a thin continuous rim-like lip and is not depressed into the umbilicus. The relict apertures of the earlier chambers are widely open, semicircular arches and can usually be easily observed within the umbilical cavity. The ventral intercameral sutures are sub-radial in direction, moderately incised and the equatorial profile is not greatly lobate so giving a general globose and tumid appearance to the test. The wall is calcareous, radial hyaline and is densely and coarsely perforate. The pores open into distinct pits which have strongly developed ridges between them. The pits are bordered by small mamelon-like rugosities formed by the confluence of the pit-ridges Size: Maximum diameter of holotype 0.45 mm.
Extra details from original publication The holotype of this taxon is that specimen figured as Globigerina ampliapevtura euapertura by Blow and Banner (1962, loc. cit.). Several paratypes are figured here by electron-microscope stereoscan techniques and these figures show clearly the nature of the wall structure and texture. It will be seen that the nature of the wall of G. prasaepis is very close to that of G. ampliapertura and the former is considered to have developed from the latter taxon in the later parts of Zone P. 1 7 [ = Globigerina gortanni gortanni - Globorotalia (Turborotalia)centralis Partial-range zone] . The unmodified aperture of G. prasaepis distinguishes the taxon from G. pseudopenezuelana which possesses a distinct apertural tooth-like flap. Globigerina euapertura also differs from G. prasaepis in having a restricted aperture and a well developed apertural lip. Globigerina euapertura Jenkins seems to be limited to colder water environments and is unrelated to either G. prasaepis or G. ampliapertura. Bolii (1957, U. S. Nat. Mus., Bull., no. 215, p. 108) considered the forms described here as G. prasaepis as referable to G. cf. venezuelana, but the subspherical nature of the chambers of G. prasaepis and the trough-like nature of the aperture of the final chamber serves to distinguish this taxon from Hedbergs's G. venezuelana. The trival name of the taxon refers to the trough-like nature of the aperture.
Blow, W. H. (1969). Late middle Eocene to Recent planktonic foraminiferal biostratigraphy. In, Bronnimann, P. & Renz, H. H. (eds) Proceedings of the First International Conference on Planktonic Microfossils, Geneva, 1967. E J Brill, Leiden 380-381. gs
Pearson, P. N. & Wade, B. S. (2015). Systematic taxonomy of exceptionally well-preserved planktonic foraminifera from the Eocene/Oligocene boundary of Tanzania. Cushman Foundation for Foraminiferal Research, Special Publication. 45: 1-85. gs
Wade, B. S., Pearson, P. N., Olsson, R. K., Fraass, A. J., Leckie, R. M. & Hemleben, C. (2018c). Taxonomy, biostratigraphy, and phylogeny of Oligocene and Lower Miocene Dentoglobigerina and Globoquadrina. In, Wade, B. S., Olsson, R. K., Pearson, P. N., Huber, B. T. & Berggren, W. A. (eds) Atlas of Oligocene Planktonic Foraminifera. Cushman Foundation for Foraminiferal Research, Special Publication . 46(Chap 11): 331-384. gs
Globigerina prasaepis compiled by the pforams@mikrotax project teamviewed: 9-6-2023