CATALOG OF ORIGINAL DESCRIPTIONS: Globorotalia (Turborotalia) pseudoinconstans 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) pseudoinconstans
Other pages this level: << < 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) pseudoinconstans

Citation: Globorotalia (Turborotalia) pseudoinconstans Blow 1979
Rank: Species
Type locality: DSDP Site 47/2, at a depth of 2689 meters on the Shatsky Rise, lat. 32°26.9' N., long. 157°42.7' E., northwestern Pacific Ocean; holotype (pl. 6, 7, fig. 4) and one paratype (fig. 3) from sample 11/3, 148-150 cm; paratype (pl. 69, fig. 4) from same sample, 0-5 cm; paratype (fig. 9a-c) from blue-black micaceous clay in road cut on Alabama Highway 28, 0.8 mi. west of the Alabama River Bridge, Wilcox County, Alabama.
Type age (chronostrat): Lowermost Paleocene, lower Danian, Zone Pa (Globorotalia (Turborotalia) longiapertura partial-range zone). Paratype (pl. 69, fig. 4) from the lower part of lower Danian, Zone P.la (Globorotalia (Turborotalia) pseudobul loides/ Globorotalia (Turborotalia) archaeocompressa concurrent-range subzone, and paratype (fig. 9a-c) from lower Paleocene, lower Danian
Type sample (& lithostrat): Pine Barren Member of Clayton Formation.
Type specimens: Holotype:PM PF 63665 Paratype:PM PF 63682
Type repository: London, UK; NHM

Linked specimens: London, UK; NHM (PM PF 63665) London, UK; NHM (63682)

Current identification/main database link: Praemurica pseudoinconstans (Blow 1979)


Original Description
The comparatively small test is coiled in a low, fairly lax, trochospire with 6 complete chambers visible in the last convolution of the test together with a small part of a seventh chamber and about 12-14 chambers comprising the spire. In dorsal aspect, the chambers are sensibly equidimensional, inflated and subglobular, with quite distinctly incised dorsal intercameral sutures; these intercameral sutures are radially disposed. In ventral aspect, the chambers are inflated, subglobular, but are slightly more embracing and appressed than as seen in dorsal aspect. The chambers increase evenly, but only slowly, in size as added in the progression of the trochospire. The umbilicus is widely open, moderately deep and clearly delimited by the umbilical shoulders of the last convolution of chambers. The primary aperture is slit-like near the umbilicus but widens to become highly arched at, or near to, the peripheral margin of the test; the aperture is bordered by a strongly developed flap-like lip proximally, which extends into the umbilical depression, Distally, the lip of the aperture is more rim-like and is less broad than seen proximally, Within the umbilicus, relict apertures are present for chambers prior to the last and their apertural lips are confluent with the lip of the ultimate chamber. The equatorial profile is subcircular to slightly elongate in the direction of the diameter which bisects the final chamber; the equatorial profile is also moderately lobulate. The axial-apertural profile shows an equally biconvex test with rounded peripheral margins. The wall texture of the test is finely and densely perforate and, over the earlier chambers of the last whorl, the mural-pores open into small pore-pits. The inter-pore ridges show a meandriform pattern which is characteristic.

Size: Maximum diameter of holotype 0.328 mm as measured by electron beam sensor.

Extra details from original publication

This rather small form frequently shows the presence of between 6 and 7 chambers in the last convolution of its test and this multicamerate nature of the form parallels that seen for Globorotalia (Turborotalia) inconstans (Subbotina) [Globigerina inconstans, 1953]. However, the two forms are easily distinguished by the more slowly increasing size of the chambers as added in the trochospire of pseudoinconstans as well as the relatively more open umbilicus, more sharply incised inter-cameral sutures and the peculiar wall texture of meandriform inter-pore ridges seen in pseudoinconstans as compared to the corresponding characters of inconstans. Furthermore, the shape of the aperture is a particular feature of pseudoinconstans and this is very well illustrated in the specimen figured by Loeblich and Tappan (fig. 9a-c) which is here considered as a paratype of the writer's new taxon. The illustrations given by Loeblich and Tappan (ibid) particularly well display the gross charac ters of the taxon pseudoinconstans including not only the apertural characters but also the slow increase in size of the chambers in the last whorl.

"The paratype figured here in fig. 3 shows seven complete chambers in the last whorl and also shows very clearly the characteristic pattern of meandriform inter-pore ridges which run confluently in an irregular manner. Because of these irregularly meandriform inter-pore ridges, the pore-pits do not have the usual 'honeycomb' appearance so frequently seen in specimens referable to the Globigerinacea. The mural-pores are very fine with small diameters but are densely and closely packed. The paratype on pl. 69, fig. 4, shows an unusually large final chamber but, as can be seen from an analysis of the earlier test, the rate of chamber enlargement is similar to that seen in the holotype for all chambers prior to the last.

Although, in general morphology the forms referred to pseudoinconstans show similarity to the morphotypes included in G. (T.) polycamera (Khalilov) [Globigerina edita Subbotina var. polycamera, 1956], pseudoinconstans possesses more sharply incised sutures, less embracing and closely appressed chambers as well as a completely different wall texture [compared] to the morphotypes referable to polycamera.

 

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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) pseudoinconstans compiled by the pforams@mikrotax project team viewed: 25-10-2020

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