Globigerina juvenilis Bolli 1957 (TaxonConcept

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Species Globigerina juvenilis Bolli 1957

Diagnosis / Definition:

Bolli (1957):
Shape of test moderately to distinctly trochospiral; equatorial periphery distinctly lobate. Wall calcareous, perforate, surface smooth to very finely pitted. Chambers spherical to ovate; about 12, arranged in about 3 whorls; the 3-4 chambers of the last whorl increase rapidly in size. Sutures on spiral side curved to radial in the early stage, radial in the last whorl, depressed; on umbilical side radial, depressed. Umbilicus very small. Aperture a low elongate slit, often with a thin lip; interiomarginal, umbilical. Coiling random. Largest diameter of holotype 0.29 mm.

Discussion / Comments:

Bolli (1957):
Globigerina juvenilis, new species, appears to be related to G. bradyi Wiesner, but is less distinctly trochospiral. Transitional forms between the two species may be observed. It is also possible that Globigerina juvenilis represents the juvenile stage of Globigerinita naparimaensis Bronnimann, where the bulla is not yet developed (for comparison see Bolli, Loeblich and Tappan, 1957, pl. 8, figs. 1a-c).
Jenkins (1985):
G. juvenilis is a small, low spired, smooth walled species with a lipped, umbilical aperture. Forms with an umbilical bulla have been referred to Globigerina incrusta and G. glutinata (Jenkins, 1971, 1978c). In the present author's opinion G. juvenilis evolved from Globorotalia munda Jenkins in the late Early Oligocene of New Zealand (Jenkins, 1966a). This event was later observed also at DSDP Leg 29 Sites 277 and 282 as well as at Leg 40 Site 360 (Jenkins, 1975, 1978c). The first evolutionary appearance of G.juvenilis in these areas is therefore considered to be a good stratigraphic marker.

Systematics:

22
Genus Globigerina
Species Globigerina juvenilis

Synonym list:

Bolli (1957):

1957 Globigerina juvenilis Bolli. - Bolli : pl. 24, figs. 5a-6 new species

Jenkins (1985):

1957 Globigerina juvenilis Bolli. - Bolli : p.110 pl. 24, figs. 5a-c

1985 Globigerina juvenilis Bolli. - Jenkins : p.277 figs. 7.1; 5

Was used in synonym list of:

Globigerinita juvenilis Bolli 1957

References:

Bolli,H.M. (1957):
Planktonic foraminifera from the Oligocene-Miocene Cipero and Lengua formations of Trinidad, B.W.I..
In: Studies in Foraminifery, Bulletin of the U.S. National Museum Vol. 215 Eds: Loeblich, A.R.Tappan, H.Beckmann, J.P.Bolli, H.M.Gallitelli, E.M.Troelsen, J.C. p. 97-123

Jenkins,D.G. (1985):
Southern mid-latitude Paleocene to Holocene planktic foraminifera.
In: Plankton stratigraphy Eds: Bolli, H.M.Saunders, J.B.Perch-Nielsen, K. p. 263-282

Anonymous: Unedited TaxonConcept data

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