CATALOG OF ORIGINAL DESCRIPTIONS: Globorotalia (Turborotalia) pseudoimitata Blow 1979

This page provides data from the catalog of type descriptions. The catalog is sorted alphabetically. Use the current identification link to go back to the main database.


Higher levels: pf_cat -> G -> Globorotalia (Turborotalia) -> Globorotalia (Turborotalia) pseudoimitata
Other pages this level: << < G. (Turborotalia) humerosa praehumerosa, G. (Turborotalia) incisa, G. (Turborotalia) longiapertura, G. (Turborotalia) mendacis, G. (Turborotalia) nkbrowni, G. (Turborotalia) oceanica, G. (Turborotalia) palpebra, G. (Turborotalia) parkerae, G. (Turborotalia) peripheroacuta, G. (Turborotalia) peripheroronda, G. (Turborotalia) permicra, G. (Turborotalia) planispira, G. (Turborotalia) pliocenica, G. (Turborotalia) praecentralis, G. (Turborotalia) praeoscitans, G. (Turborotalia) pseudoimitata, G. (Turborotalia) pseudoinconstans, G. (Turborotalia) pseudokugleri, G. (Turborotalia) pseudopumilio, G. (Turborotalia) quadrilocula, G. (Turborotalia) rainwateri, G. (Turborotalia) riedeli, G. (Turborotalia) rikuchuensis, G. (Turborotalia) tosaensis tenuitheca, G. (Turborotalia) transsylvanica, G. (Turborotalia) variospira,

Globorotalia (Turborotalia) pseudoimitata

Citation: Globorotalia (Turborotalia) pseudoimitata Blow 1979
Rank: species
Type locality: Holotype (fig. 10) and eleven paratypes (pl. 106, figs. 2-9; pl. 108, figs. 1-3) from DSDP Site 20C, sample 6/3, 76-78 cm, cored at a depth of 4506 meters on the western flank of the Mid-Atlantic Ridge, lat. 28°31.47' S., long. 26°50.73' W., in the South Atlantic Ocean; also three paratypes (pl. 101, figs. 1-3) from DSDP Site 47/2, sample 9/1, 64-66 cm, cored at a depth of 2689 meters on the Shatsky Rise, lat. 32°26.9' N., long. 157°42.7' E., northwestern Pacific Ocean.
Type age: Upper Paleocene, upper Londinian [upper Thanetian], [lower] Zone P.6 (Globorotalia (Morozovella) subbotinae subbotinae - Globorotalia (Mor ozovella velascoensis acuta partial-range zone); three paratypes (p1. 101, figs. 1-3) from Upper Paleocene, upper Thanetian, Zone P.5 (Muricoglobigerina soldadoensis soldadoensis/ Globorotalia (Morozovella) velascoensis pasionensis concurrent-range zone). Ranges up to within the upper part of Lower Eocene, lower Ypresian, Zone P.7 (Globorotalia (Acaranina) wilcoxensis berggreni partial-range zone).
Holotype Repository: London, UK; NHM
Type & figured specimens: Holotype:PM PF 64026 Paratype:PM PF 64018

Linked specimens: London, UK; NHM (PM PF 64026) London, UK; NHM (64018)

Current identification/main database link: Globorotaloides eovariabilis Huber & Pearson, in Olsson et al. 2006


Original Description
The fairly small test is coiled in a low, but tight, tro chospire with about 10-12 chambers comprising the spire and with four normal chambers as well as a reduced fifth chamber in the last convolution of the test. In dorsal aspect, the chambers are closely appressed and embracing but the periph eral surfaces of the chambers are inflated and rounded. The dorsal surface of the test is slightly flattened but the individual dorsal surfaces of the chambers remain smoothly rounded. The chambers in dorsal aspect are considerably longer tangen tially than broad radially and are lunate in shape. The dorsal intercameral sutures are slightly depressed and are recurved for the earlier chambers but in the later chambers of the last whorl, the dorsal intercameral sutures are subradially disposed to distally retorse. In ventral aspect, the ventral intercameral sutures are radially disposed, slightly incised to broadly depressed. In ventral aspect, the chambers are almost equidimensional with broadly rounded ventral surfaces which extend in lobe-like extensions towards the umbilicus. In this aspect, the chambers appear more embracing and appressed than they do in dorsal aspect. The umbilicus is very small and shallow and is not clearly delimited by the umbilical shoulders of the last convo lution of chambers. The holotype possesses a reduced final chamber and the primary aperture is a very low, quite strongly lipped, slit-like, opening extending from the umbilicus to about two-thirds of the way towards the peripheral margin. The axial apertural profile is smoothly rounded whilst the equatorial profile is gently lobulate. The wall of the test is generally quite coarsely perforate with large mural-pores but the ventral surface of the test has mural-pores of small diameters and these pores are less densely packed. The mural-pores do not open into well defined pore-pits in the holotype and the inter-pore ridges are only very poorly delimited. Maximum diameter of holotype 0.252 mm as measured by electron beam sensor.

Size: Maximum diameter of holotype 0.252 mm as measured by electron beam sensor.

Extra details from original publication

Loeblich and Tappan (1957, U. S. Nat. Mus., Bull., no. 215, pl. 59, figs. 5a-e and pl. 63, figs. 3a-c) figured two specimens referred by them to Globorotalia imitata which are considered here as, most likely, referable to Globorotalia (Turborotalia) pseudoimitata Blow, 1979. Whilst there is little doubt that the specimen figured on their pl. 63 is referable to pseudoimitata, the specimen on their pl. 59 is a little more doubtfully included in pseudoimitata since it shows a somewhat wider umbilicus than typically seen in the writer's own specimens. However, this later specimen may be, possibly, a little more phylogenetically and morphologically primitive than the more typical forms discussed in this work.
The paratypic specimens figured on pl. 106, figs. 2-9, illustrate the general morphology and range of variation which the writer associated with his new taxon. The specimen figured in dorsal aspect in fig. 8 shows a form which, like the holotype, has a small reduced final chamber. The two paratypes figured in figs. 7 and 8, show the typical axial-apertural and dorsal aspects of the morphotypes included in the taxon. The paratype figured in fig. 5, shows a form with a more normal final chamber and also shows the strongly developed apertural flap-like lip with the aperture extending around the umbilical margin of the final chamber to about half-way towards the peripheral margin. In many specimens referable to pseudoimitata Blow, 1979, the final chamber shows a strong lobe-like extension partially obscuring the small umbilicus; the shape of the final chamber also appears to approach the morphology of an ampulla (sensu Blow, 1979, op. cit., p. 469-471) which is characteristic of the Neogene genus Turborotalita Blow and Banner, 1962, however, true ampullae are not developed in pseudoimitata Blow, 1979.

The paratypes figured on pl. 101, figs. 1-3, show the variation of size in mural-pores between the dorsal and ventral surfaces of the test. These specimens also have quite large pore-pits but the inter-pore ridges are still (as usually seen) rather poorly defined. The paratypes illustrated on pl. 108, figs. 1-3, show converse features to the characters of the wall noted for the specimens figured on pl. 101. In the paratypic specimens figured on pl. 108, figs. 1-3, the mural-pores are consistently small for both the dorsal and ventral surfaces of the tests. It would seem that in the later stages of calcification further test material may either be laid down in sheet-like masses (cf. pl. 108, fig. 1) which partially obscure the mural-pores or, alternatively, be laid down in such a way to emphasize the cancellate nature of the test surface (cf. p1. 101, figs. 1 and 2 especially). The irregularly disposed, discontinuously sheet-like nature of later calcified test material can also be seen in the holotype (fig. 10) where this later calcification is developed over the ventral surface of the test.

Globorotalia (T.) pseudoimitata Blow, 1979, differs from G. (T) imitata Subbotina by having more closely appressed and embracing chambers, a tighter coiling-mode and a smaller, almost closed umbilicus. In dorsal aspect, the chambers of pseudoimitata are longer (tangentially) than those of imitata and the equatorial profile is less markedly lobulate in the writer's new taxon as compared to the morphotypes included in Subbotina's taxon. Notwithstanding a very broad general morphological similarity between the two forms, the writer has not seen any morphotypes which would connect the forms phylogenetically and pseudoimitata is, at present, thought to be homeomorphic rather than closely genetically related to imitata Subbotina.

References:

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


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Globorotalia (Turborotalia) pseudoimitata compiled by the pforams@mikrotax project team viewed: 26-9-2020

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