 Hornibrook et al. 1989, Fig. 26.18a-e: 0.47 mm |
 Hornibrook et al. 1989, Fig. 28.14: 0.47 mm |
Reference: Hornibrook, Brazier & Strong 1989, p.128, Fig. 26:18a-e, 28:14.
Synonymy: 1936, Globorotalia dehiscens, jl. Linn. Soc. (zool.) 38(262): 569, pl. 11, fig. 36a-c;
1947, Globoquadrina subdehiscens, Finlay, N.Z. jl. sci. techn. B28(5): 291;
1961, G. dehiscens, Hornibrook, N.Z. Geol. Surv. paleont. bull. 34(1): 153, pl. 22, fig. 446, 447;
1971, Jenkins, Ibid. 42: 165, 166, pl. 20, fig. 595-597; 1978, Hornibrook, N.Z. jl. geol. geophys. 21(5): 657-659, fig. 1-9;
1983, Kennett & Srinivasan, Neogene Planktonic Foraminifera, p. 184, pl. 44, fig. 2, pl. 45, fig. 7- 9, text-fig. 20.
Description: In its most characteristic form, G. dehiscens, is subquadrate with four chambers with rather flattened inner faces in the final whorl; sutures incised and surfaces with a distinctive subhexagonal pore pattern; aperture a low arched slit and a plate-like lip extending into an open umbilicus.
Distribution: Waitakian to Tongaporutuan.
Comment: This form is the one usually illustrated as an important marker species for the base of the Miocene. In the Miocene of New Zealand, however, populations of G. dehiscens include also much more inflated individuals which tend to dominate in more oceanic environments and kummerform chambers resembling apertural bullae covering the aperture, are commonly present. Fig. 26:18 a-e illustrates a range of test shapes in a typical population from the Gee Greensand at Kakanui (Otaian Stage, Lower Miocene). Populations from more oceanic facies below the base of the range of G. dehiscens in the Duntroonian (Upper Oligocene) become progressively more inflated and resemble G. praedehiscens Blow. In New Zealand, the highest records of the continuous occurrence of G. dehiscens are in the Tongaporutuan (Fig. 28:14), significantly earlier than Pliocene records in low latitudes.
Cite this publication as: "Strong CP, Raine JI, Terezow M. 2018. Key
species of New Zealand fossil foraminifera: descriptions from "Manual of New
Zealand Permian to Pleistocene Foraminiferal Biostratigraphy" by Hornibrook,
Brazier and Strong, 1989. Lower Hutt (NZ): GNS Science. (GNS Science
miscellaneous series; 123)."
ISSN 1172-2886, ISBN 978-1-98-853088-8,
DOI 10.21420/G2M63W.
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