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Globigerina prasaepis Blow 1969 from: Blow, W.H. (1969): Late middle Eocene to Recent planktonic foraminiferal biostratigraphy. In: Proceedings of the First International Conference on Planktonic Microfossils, Geneva 1967 Vol. 1 Eds: Bronnimann, P.Renz, H.H. p. 199-422
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Anonymous: Unedited TaxonConcept data
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Species Globigerina prasaepis Blow 1969


Diagnosis / Definition:
Blow (1969):
Description of holotype: The large globose test consists of about 14 chambers arranged in a low trochospire with 3 1/2 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 [62a]. 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. Maximum diameter of holotype 0.45 mm.
Discussion / Comments:
Blow (1969):
Remarks: The holotype of this taxon is that specimen figured as Globigerina ampliapertura euapertura by BLOW and BANNER (1962, see synonymy above). 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.17. The unmodified aperture of C. prasaepis distinguishes the taxon from G. pseudovenezuelana 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 (see also comments given under No. 22 in the "Check List", P. 31:9 above). Globigerina euapertura JENKINS seems to be limited to colder water environments and is unrelated to either G. prasaepis or G. ampliapertura. BOLLI (9157) [5] 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 troughlike nature of the aperture of the final chamber serves to distinguish this taxon from HEDBERG's G. venezuelana. The trivial name of the taxon refers to the trough-like nature of the aperture. Stratigraphical Range: Forms apparently transitional from Globigerina ampliapertura to G. prasaepis first occur within the middle to later parts of Zone P. 17 (uppermost Eocene) but typically developed forms only occur from just below the base of Zone P.18 and range to near the Zone N.3/Zone N.2 boundary. The holotype is described from Zone P.19 of the Lower Lukuledi formation, Tanzania, (see BLOW and BANNER, 1962) [12].
Systematics:

22
 Genus Globigerina
  Species Globigerina prasaepis
Synonym list:
Blow (1969):
1957 Globigerina ampliapertura Bolli. - Bolli : p.108 pl. 22, figs. 4a-b (not figs. 5a-7b)
1960 Globigerina euapertura Jenkins. - Jenkins : p.351 pl.1, figs. 8a-c
1962 Globigerina ampliapertura euapertura Jenkins. - Blow & Banner : p.84 pl.XI, figs.E-G (=holotype of G. prasaepis, n.sp.)
1969 Globigerina prasaepis Blow. - Blow : p.382 pl. 10, fig. 13; pl. 18, figs. 3-7
Spezzaferri & Silva (1990):
1969 Globigerina prasaepis Blow. - Blow : pl. 10, fig. 13; pl. 18, fig. 3-7
1990 "Globigerina" prasaepis Blow. - Spezzaferri & Silva : p.245 pl. VII; fig. 6a-c
Quilty (1976):
1969 Globigerina prasaepis Blow. - Blow : p.382 pl. 10, fig. 13; pl. 18, fig. 3-7
1976 Globigerina prasaepis Blow. - Quilty : p.671 pl. 3, figs. 17-18
References:

Bolli,H.M. (1957):
Planktonic foraminifera from the Oligocene-Miocene Cipero and Lengua formations of Trinidad, B.W.I..
In: Studies in Foraminifery, Bulletin of the U.S. National Museum Vol. 215 Eds: Loeblich, A.R.Tappan, H.Beckmann, J.P.Bolli, H.M.Gallitelli, E.M.Troelsen, J.C. p. 97-123

Jenkins,D.G. (1960):
Planktonic foraminifers from the Lakes Entrance oil shaft, Victoria, Australia . Micropaleontology Vol. 6(4) p. 345-371

Blow,W.H. and Banner,F.T. (1962):
The Mid-Tertiary (Upper Eocene to Aquitanian) Globigerinaceae.
In: Fundamentals of Mid‑Tertiary Stratigraphical Correlation Eds: Eames, F.E.Banner, F.T.Blow, W.H.Clarke, W.J. p. 61‑151

Blow,W.H. (1969):
Late middle Eocene to Recent planktonic foraminiferal biostratigraphy.
In: Proceedings of the First International Conference on Planktonic Microfossils, Geneva 1967 Vol. 1 Eds: Bronnimann, P.Renz, H.H. p. 199-422

Quilty,P.G.. (1976):
Planctonic foraminifera DSDP Leg 34- Nazca Plata . DSDP initial reports Vol. 34

Spezzaferri,S. and Silva,I.S.. (1990):
Oligocene planktonic foraminiferal biostratigraphy and paleoclimatic interpretation from Hole 538A, DSDP Leg 77, Gulf of Mexico . Palaeogeography, Palaeoclimatology, Palaeoecology Vol. 83 p. 217-263
Anonymous: Unedited TaxonConcept data
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