Catalog - Globorotalia (Turborotalia) rainwateri

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Globorotalia (Turborotalia) rainwateri

Citation: Globorotalia (Turborotalia) rainwateri Blow 1979

Type specimens: Paratype: PM PF 63761

Type age (chronostrat): Lower Paleocene, upper Danian, Wills Point Formation, ?Zone P.2 (Globorotalia (Acarinina) praecursoria praecursoria partial-range zone). Paratype (fig. 9a-c) from Upper Paleocene, Londinian [upper Thanetian], Vincentown Formation, Zone P.5 (Muricoglobigerina soldadoensis soldadoensis/ Globorotalia (Morozovella) velascoensis pasionensis concurrent-range zone.

Type locality: Holotype (fig. 3a-c) from clay beds in abandoned pit of the Mexia Brick Works, at Mexia, Limestone County, Texas. Paratype (fig. 9a-c) from marls on the north bank of Rancocas Creek 0.3-0.5 mi northwest of Vincentown, Burlington County, New Jersey. Paratypes (figs. 6, 7) 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.

The small test is coiled in a low, rather tight, trochospire with about 13-14 chambers comprising the spire and with five chambers in the last convolution of the test. In dorsal aspect, the chambers are only a little longer tangen tially than they are broad radially; the dorsal surfaces of the chambers are closely set but only moderately embracing and appressed. The dorsal intercameral sutures are subradially disposed, distinct but not deeply incised or depressed. The equatorial profile is subcircular and is not markedly lobulate in outline. The chambers do not increase rapidly as added in the progression of the trochospire but only increase in size very slowly, regularly and evenly. The axial-apertural profile shows the rounded peripheral margin, closely-set chambers and also shows that the initial coil of cham bers stands slightly above the level of the dorsal surfaces of the last convolution of chambers. In ventral aspect, the chambers appear more embracing and appressed than they do in dorsal aspect. The ventral surfaces of the last convolution of cham bers are inflated and the umbilicus is small, shallow and not clearly delimited by the umbilical shoulders of the last whorl of chambers. The ventral intercameral sutures are distinct, somewhat incised and subradially to sinuously disposed. The aperture extends from the umbilicus to about half of the way towards the peripheral margin and is more widely open distally than it is proximally near the umbilicus. The aperture is bordered by a comparatively strongly developed apertural lip. The wall tex ture is coarsely perforate with the mural-pores into distinct pore-pits and with distinctly defined inter-pore ridges.

Maximum diameter of holotype 0.20 mm

As noted (Blow, 1979, op. cit., p. 812) Globorotalia (Turborotalia) reissi Loeblich and Tappan, 1957, appears to consist of two different morphotypes. G. (T) rainwateri differs from the paratypic form of reissi (cf. Loeblich and Tappan, 1957, op. cit., pl. 50, fig. 3a-c) by having fewer chambers in the last convolution of the test and chambers which enlarge more quickly but which are more closely-set, embracing and appressed than in this paratypic form of reissi. Similarly, G. (T.) rainwateri differs from the holotype of reissi (cf. Loeblich and Tappan, 1957, op. cit., pl. 58, fig. 3a-c) in having chambers which are more nearly equidimensional and much less long tangentially than as seen in the holotypic form of reissi.

The paratypes figured here in figs. 6 and 7 show the coarsely cancellate nature of the wall surface which is characteristic of the taxon. These two specimens also show the rather closely-set chambers especially as seen in axial-apertural view. The [paratypic] specimen figured by Loeblich and Tappan (fig. 9a-c) also clearly shows the appressed and closely-set nature of the chambers and the almost non lobulate nature of the test in equatorial profile.

Globorotalia (Turborotalia) rainwateri Blow, 1979, differs from G. (T.) imitata Subbotina, 1953, in having a less lobulate equatorial profile, more closely-set, appressed and embracing chambers which, in dorsal aspect, are not so tangentially long as they are in G. (T) imitata. Furthermore, the chambers do not enlarge so rapidly in rainwateri as compared to imitata. G. (T) rainwateri differs from G. (T.) pseudoimitata Blow, 1979, by having chambers which are more nearly equidimensional in dorsal aspect as compared to the long chambers (tangentially) of pseudoimitata. G. (T.) rainwateri possesses a more clearly defined umbilicus than pseudoimitata and does not show any lobe-like extensions of the last chamber over, or towards, the umbilicus.

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) rainwateri Blow 1979

Globorotalia (Turborotalia) rainwateri

References:

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