Catalog - Globorotalia (Morozovella) finchi

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Globorotalia (Morozovella) finchi

Citation: Globorotalia (Morozovella) finchi Blow 1979

Type specimens: Holotype: PM PF 63962, Paratype: PM PF 63961

Type age (chronostrat): Upper Paleocene, Londinian [upper Thanetian], upper Zone P.5 (Muricoglobigerina soldadoensis soldadoensis/ Globorotalia (Morozovella) velascoensis pasionensis concurrent-range zone); ranges from lower Zone P .5 to basal Lower Eocene, lower Ypresian, middle Zone P. 7

Type locality: Holotype and five paratypes (figs. 6-1 1) from DSDP Station 47 2, sample 9 1, 64-66 cm, cored at a depth of 2689 meters on the Shatsky Rise, 320 26.9' N. , 157 0 42.7' E. , northwestern Pacific Ocean; and one paratype (Loeblich and Tappan, loc. cit.) from Hornerstown Formation, north bank of Shingle Run on Crosswicks Creek, I mi. north of New Egypt, Monmouth County, New Jersey.

The test is coiled in a moderately low trochospire with about 13 muricate chambers comprising the spire and with 6, not rapidly enlarging, chambers visible in the last convolution of the test. The chambers in dorsal aspect are distinctly tangentially longer (anterior-posteriorly) than radially broad; the dorsal intercameral sutures are recurved, not pseudo-limbate, but are quite strongly muricate. The equatorial profile is lobate and the axial-apertural profile shows an unequally biconvex test. The dorsal side is slightly convex with the initial whorl of chambers raised above the general level of the last convolution of chambers. The ventral side is convex and the chambers of the last whorl, in ventral aspect, are cuneiform with radially disposed intercameral sutures which are moderately incised and distinct. The peripheral margin is acute and bears a peripheral test muricocarina which is not strongly developed. The umbilicus is small, but open and comparatively deep. The primary aperture is a low arch extending from the umbilicus to near the peripheral margin.

Maximum diameter of holotype, 0.32 mm.

Remarks. - The paratypes illustrated by the writer in figs. 6-10 illustrate the range of variation associated with the new taxon. Fig. 7 shows a paratype with 7 chambers in the last convolution of the test, which, like the specimen figured by Loeblich and Tappan (1957, loc. cit.) and now referred to as a paratype of the writer's new taxon finchi, show the typical slow rate of chamber enlargement for the chambers of the last convolution. However, the paratype illustrated on fig. 9 shows a slightly greater rate of chamber enlargement and about 5 1/2 chambers in the last convolution of the test. Figs. 8 and 10 show the variation in axial profile which ranges from an acute peripheral margin (fig. 10) to a subrounded peripheral margin (fig. 8) but always with a muricocarina. The specimen figured by Loeblich and Tappan (1957 loc. cit.) possesses a thin-walled, reduced final chamber which (cf. their fig. 5c) does not bear a peripheral test muncocarina although the earlier parts of the last convolution of the test is weakly muricocarinate. Globorotalia (Acarinina) trichoirocha Loeblich and Tappan (1957, op. cit., pl. 57, figs. l, 2; see Blow, 1979, op. cit., p. 963), Loeblich and Tappan's taxon appears to be directly ancestral to Globorotalia (Morozovella)finchi Blow. The latter taxon develops from trichlrocha by the acquisition of a muricocarina and the development of a more acute peripheral margin combined with dorsal flattening of the later chambers especially.
'Globorotalia (M.) finchi is a small, but quite distinctive, form and cannot be easily confused with any other taxon. However, there is a very slight resemblance to G. (M.) subbotinae gracilis Bolli [see Globorotalia formosa gracilis, 1957], but the smaller umbilicus, more slowly enlarging chambers, less well developed muricocarina and consistently smaller overall test size (for a given stage of ontogeny) are all features which separate finchi from gracilis. In comparison to G. (M.) occlusa (sensu lato), the weakly developed muricocarina, recurved later dorsal intercameral sutures without pseudolimbation, and the generally rather biconvex, consistently smaller test size, again provide a basis for easy taxonomic differentiation of finchi

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

CATALOG OF ORIGINAL DESCRIPTIONS: Globorotalia (Morozovella) finchi Blow 1979

Globorotalia (Morozovella) finchi

References:

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