Catalog - Globorotalia (Turborotalia) quadrilocula

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Globorotalia (Turborotalia) quadrilocula

Citation: Globorotalia (Turborotalia) quadrilocula Blow 1979

Type specimens: Holotype:PM PF 63856 Paraype:PM PF 63741

Type age (chronostrat): Middle Paleocene, lower Thanetian, Zone P.3 (Globorotalia (Mor ozovella) angulata angulata partial-range zone). Paratype (pl. 75, fig. 8) from Lower Paleocene, lower Danian, subzone P Ib; and four paratypes (pl. 78, figs. 2-4; pl. 83, fig. 3) from Lower Paleocene, upper Danian, Zone P.2.

Type locality: Holotype (pl. 87, fig. 7) and one paratype (pl. 87, fig. 8) from sample 10/1, 72-74 cm and paratype (pl. 83, fig. 3) from sample 10/3, 78-80 cm, both cored at a depth of 2689 meters on the Shatsky Rise, lat. 32°26.9' N., long. 157°42.7' E., northwestern Pacific Ocean. Three paratypes (pl. 78, figs. 2-4) from DSDP Site 20C, sample 6/4, 72-74 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. One paratype (pl. 75, fig. 8) from Lindi area, Tanzania. One paratype (figs. 22-24) from core between 4,524-4,536 ft. in Lizard Springs Formation Guayaguayare Well 159, Trinidad.

The test is coiled in a low, fairly tightly coiled, trocho spire with about 11-12 chambers comprising the spire and four complete chambers visible in the last convolution of the test; a small part of a fifth chamber is also present in the final convolution. In dorsal aspect, the chambers are subglobular, slightly appressed and embracing, and are approximately equidimensional. The dorsal intercameral sutures are moderately incised, clearly marked and radially dis posed. In ventral aspect, the chambers are inflated and the ventral intercameral sutures are deeply incised and radially disposed. The umbilicus is small, but deep, and the primary aperture extends from the umbilicus to about three-quarters of the way towards the periphery; the aperture is bordered by a distinct apertural flap which is broader proximally than it is distally. In equatorial profile, the test is lobu late and subcircular in outline, whilst in axial-apertural profile the test is smoothly rounded. However, in axial profile it can be seen that the dorsal side of the test is slightly flattened but otherwise the test can be considered as sensibly equally bi convex. The wall is coarsely cancellate with quite large mural-pores which open into distinct pore-pits surrounded by quite well defined inter-pore ridges.

Maximum diameter of holotype 0.314 mm as measured by electron beam sensor.

The range of variation shown for this taxon is displayed by reference to the specimen (here considered paratypic) figured by Bolli (1957, loc. cit.) and by the paratypes figured in this work. The two paratypes figured on pl. 78, figs. 2 and 3, show ventral aspects of the taxon including the small umbilicus (partially infilled by matrix in fig. 2), coarsely cancellate wall texture and rather more closely appressed chambers than seen in the holotypic specimen. The axial-apertural view of a paratype shown on pl. 78, fig. 4, also displays rather more appressed and embracing chambers than seen in the holotype. This specimen also has a particularly coarsely cancellate wall texture with large pore-pits. On the other hand, the paratype figured on pl. 83, fig. 3, has chambers (in ventral aspect) which embrace and are appressed to about the same degree as in the holotypic specimen but has a smaller umbilicus and a less coarsely cancellate wall texture (with smaller pore-pits) than in the holotype; the wall texture of this paratype on pl. 83, fig. 3, is, of course, much less coarsely perforate than the paratypes discussed above. Furthermore, pl. 83, fig. 3, shows the presence of small `spinosities' and pustules over part of the ventral surface of the paratype. However, these pustules and spinosites are not to be considered as muricae but are more like the normal spine-bases seen in the Neogene/ Anthropogene forms of the Globigerinacea. The [paratypic] specimen figured by Bolli (1957, loc. cit.) appears to stand quite close to the holotype in all aspects of its morphology except that its last chamber is reduced in size and its direction of coiling is opposite to that of the holotype. The paratypes figured on pl. 75, fig. 8 and p1. 87, fig. 7, are both shown in dorsal aspect; the specimen figured on pl. 75, fig. 8 shows the earlier chambers very clearly.

References:

Blow, W. H. (1979). 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. E. J. Brill, Leiden. 2: 1-1413. gs

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

Globorotalia (Turborotalia) quadrilocula

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