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Species Globorotalia (Turborotalia) subcretacea Blow 1969



Alternative name:
Globorotalia subcretacea Blow 1969
Diagnosis / Definition:
Blow (1969):
Note: LOMNICKI quoted the figures of BRADY, 1884, as being drawings of his form G. subcretacea and placed BRADY'S specimens in direct synonymy. LOMNICKI (1900) figured a specimen which is obviously conspecific with the specimen figured by BRADY but did not refer to it as type of G. subcretacea in his subsequent 1901, publication. Therefore, BRADY'S specimen as figured together with any material labelled by BRADY prior to 1884 must be considered as equally syntypic as LOMNICKI'S own specimens the whereabouts of which are unknown. In the collections of the British Museum (Natural History) there exists a slide labelled "Globigerina (cretacea D'ORBIGNY?), Challenger Stn. 191A, off Ki Islands, 580 fathoms, ZF.1475. Rep. Voy. Challenger, vol. IX, P. 596, pl. 82, fig. 10' in BRADY's handwriting. This slide originally contained 25 specimens and a lectotype has been selected and designated from this syntypic series. It was hoped that it would have been possible to designate the specimen figured by BRADY as the lectotype but all the 25 specimens were so closely alike that it was not possible to unambiguously identify the actual specimen figured. However, all BRADY'S specimens are equally syntypic so that the designation and selection of another specimen as lectotype is of no taxonomic consequence. The lectotype has now been separated into an individual single celled slide which is registered at the British Museum (Natural History) as number 1965.2.1.1. Description of lectotype: The large test is coiled in a low trochospire and consists of about io ii chambers with five chambers comprising the final convolution. The first two, or possibly three, chambers are extremely indistinct due to some thickening of the dorsal surfaces of the chambers. The chambers are inflated, subglobular, slightly appressed and only little embracing. The equatorial profile is moderately lobulate but the axial profile is smoothly rounded. The spiral suture is depressed and incised whilst the dorsal intercameral sutures are radial in direction. The ventral intercameral sutures are radially disposed and distinctly incised between the inflated ventral surfaces of the chambers. The umbilicus is widely open and deep; the relict apertures of some of the earlier chambers can be seen within the umbilicus. The aperture of the final chamber is a moderately high arched opening, interiomarginal, umbilical extraumbilical in position. The moderately arched final aperture tends to be somewhat laterally restricted and, thus, superficially approaches a globigerine condition but it is sufficiently extraumbilical in position for the species to be referable to Globorotalia (Turborotalia). The aperture does not possess any distinct lip or rim. The wall is calcareous, radial hyaline [62a] and is rather densely and moderately coarsely perforate with the pores opening into distinct pore pits. Wall not pustulate except weakly so over the umbilical shoulders of the earlier chambers of the last whorl. Maximum diameter of lectotype o.65 mm. Note: the lectotype has been damaged and shows broken surfaces over the ultimate and penultimate chambers.
Discussion / Comments:
Blow (1969):
Remarks: This form seems to show very little variation and appears to be quite distinct morphologically. Some forms referred to subcretacea by authors are now considered to be referable to G. (T.) acostaensis humerosa but with the establishment of the lectotype no confusion between subcretacea and humerosa need result in future work. The taxon seems to be of frequent occurrence in the Indo Pacific Province but, as yet, the writer has not noted the occurrence of typical forms in the Atlantic/Caribbean Province. Stratigraphical Range: Ranges from within the early part of Zone N.21 to Zone N.23. Some rarely occurring, but not quite typical, forms appear in the later parts of Zone N.20.
Synonym list:
Blow (1969):
1884 Globigerina cretacea d'Orbigny. - Brady : p.596 pl. 82, fig. 10 (syntype, now paralectotype)
1900 Globigerina cretacea d'Orbigny. - Lomnicki : figs. 2a-c
1901 Globigerina subcretacea Lomnicki. - Lomnicki : p.17 (no figs.)
1969 Globorotalia (Turborotalia) subcretacea Blow. - Blow : p.392 pl. 4, figs. 18-20
References:

Brady,H.B. (1884):
Report on the foraminifera dredged by H.M.S. Challenger during the years 1873-1876.
In: Report of the scientific results of the voyage of H.M.S. Challenger, 1873-1876, Zoology Vol. 9 p. 1-814

Lomnicki,J.L.M. (1900):
Przyczynek do znajomosci fanny otwornic Miocenu Wieliczki . Kosmos (Lemberg) Vol. 24 p. 220-28

Lomnicki,J.L.M. (1901):
Einige Bemerkungen zum Aufsatze: Die miozšnen Foraminiferen in der Umgebung von Kolomea. . Verb. naturforsch. Ver. Brunn Vol. 39 p. 15-18

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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