CATALOG OF ORIGINAL DESCRIPTIONS: Globorotalia (Turborotalia) praecentralis 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) praecentralis
Other pages this level: << < G. (Turborotalia) griffinae, G. (Turborotalia) hansbollii, 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) praecentralis

Citation: Globorotalia (Turborotalia) praecentralis Blow 1979
Rank: Species
Type locality: DS DP Site 47/2, sample 8/1, 77-79 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 (chronostrat): Lower Eocene, upper Ypresian, Zone P.8b (Globorotalia (Morozovella) aragonensis / Globorotalia (Morozovella) formosa concurrent-range subzone). Ranges to the top of the lower Middle Eocene, lower Lutetian, Zone P.11 (Globigerapsis kugleri/Subbotina frontosa bovveri concurrent-range zone).
Type specimens: Holotype:PM PF 64270 Paratype:PM PF 64273
Type repository: London, UK; NHM

Linked specimens: London, UK; NHM (PM PF 64270) London, UK; NHM (64273)

Current identification/main database link:


Original Description
The test is coiled in a low, fairly tight, trochospire with 5 chambers visible in the last convolution of the test and with about 12-13 chambers comprising the total spire. In dorsal aspect, the chambers are tangentially longer than radially broad and are closely appressed and embracing. The peripheral surfaces of the later chambers, at leat, are inflated and smmothly rounded so that in axial-apertural aspect the test appears ovoid. In equatorial profile, the test is slightly lobulate but is generally circular in overall outline. The dorsal intercameral sutures are recurved posteriorly and are depressed but not incised. The umbilicus is small, but open and deep, and the primary aperture extends from the umbilicus to about two-thirds of the way towards the peripheral margin of the test; the aperture is a low arch near the umbilicus but widens to become a moderately high arched opening towards the distal part (peripheral) part. Ventrally, the chambers surfaces are inflated whilst dorsally the chamber surfaces are slightly flattened or depressed. The coiling-mode is fairly tightly expressed. The wall surface is more coarsely perforate over the earlier chambers of the last convolution than over the surfaces of the last or latter chambers. In the early part of the last convolution, the mural-pores open into distinct pore-pits with fairly well defined inter-pore ridges but the last chamber, especially, does not have any significant development of inter-pore ridges or pore-pits. The aperture is bordered by an extremely thickened rim which broadens umbilically into a narrow lip; the apertural rim and lip appear to be directly reflexed parts of the primary chamber wall. 

Size: Maximum diameter of holotype 0.295 mm as measured by electron beam sensor.

Extra details from original publication

The general morphology of Globorotalia (Turborotalia) praecentralis Blow, 1979, is similar in gross aspect to that of Globortalia (T.) centralis Cushman and Bermudez. However, praecentralis differs from centralis in possessing a more tightly expressed coiling-mode, more embracing and more closely appressed chambers as seen in dorsal aspect especially, as well as in having a proportionately smaller umbilicus and less widely open aperture. Whereas, in G. (T) centralis, the mural-pores are generally of the same dimensions (proportionately) as they are in praecentralis, the latter form usually has distinct pore-pits present on the surfaces of the earlier chambers. On the other hand, the morphotypes referable to centralis have only very small pore-pits without distinct inter-pore ridges. Nevertheless, in praecentralis the last (or latter) chamber usually shows the absence of pore-pits even when they are strongly developed in the earlier chambers (cf. figs. 8 and 9, also figs. 1, 5, and 6). G. (T) praecentralis evolves slowly and gradually into G. (T.) centralis within the interval of Zone P.11 and this morphogenesis involves only the relaxation of the coiling-mode and the gradual reduction of the pore-pits both in size and density. . . .

"Whilst G. (T.) praecentralis is directly ancestral to G. (T) centralis, the morphotype is also phylogenetically ancestral to G. (T.) pseudomaveri Bolli, 1957. Thus, G. (T) pseudomayeri retains the tight coiling-mode seen in praecentralis but adopts a somewhat higher spire and a shallow, almost closed, umbilicus (cf. Bolli, 1957, U. S. Nat. Mus., Bull., no. 215, pl. 37, figs. 17a-c, and the metatype figured herein on pl. 248, fig. 11). Furthermore, G. (T.) pseudomayeri not only has dorsally appressed and embracing chambers but the ventral side shows this feature to a greater extent than seen in praecentralis Blow, 1979. Again, the aperture in praecentralis is of the same general type as seen in centralis (but not quite so widely and evenly open both dorsally and proximally), however, in pseudomayeri, the aperture is a uniformly, lowly open, slit-like opening. Finally, pseudomaveri shows narrow wedge-like chambers in ventral aspect and sensibly equidimensional chambers as seen in dorsal aspect, as compared to the distinctly tangentially longer chambers seen in dorsal aspect of praecentralis. G. (T) praecentralis has less narrowly wedge-shaped chambers in ventral aspect as compared to those of pseudomaveri. In the paratypic suite of specimens figured in this work, the paratype illustrated in fig. 5 shows characters which connect the typical praecentralis to pseudomayeri Bolli. However, this specimen is still considered referable to praecentralis since, in particular, it possesses the more widely open aperture and less narrowly wedge-shaped chambers in ventral aspect as compared to those of pseudomayeri.

"

Editors' Notes
Problematica - Blow's illlustrated specimens, which are all from his Subzone P8b of DSDP Site 47 are hard to place, although we reject any relation to Turborotalia. Although well illustrated and described, the material is only moderately well-preserved. The species, which seems to have a cancellate pustulose wall, may be referable to Acarinina or even Praemurica. Blow did not provide positive evidence of his species ranging up into the middle Eocene, although he claimed that it does so, and we have not found comparable morphotypes in our researches.

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

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