Catalog - Globuligerina altissapertura

CATALOG OF ORIGINAL DESCRIPTIONS: Globuligerina altissapertura Apthorpe 2020

This page provides data from the catalog of type descriptions. The catalog is sorted alphabetically. Use the current identification link to go back to the main database.


Higher levels: pf_cat -> G -> Globuligerina -> Globuligerina altissapertura
Other pages this level: G. altissapertura, G. bathoniana australiana, G. bathoniana gigantea, G. calloviensis, G. caucasica, G. frequens, G. glinskikhae, G. gulekhensis, G. hungarica, G. meganomica, G. neilii, G. parva, G. parva Kuznetsova, G. stellapolaris, G. tojeiraensis, G. umbilicata, G. waskowskae

Globuligerina altissapertura

Citation: Globuligerina altissapertura Apthorpe 2020
Rank: Species
Described on page(s) : 102-
Type specimens: Fig. 4: 1–12; Fig. 6: 1–3; Fig. 7: 5–6; Fig. 8: 1–8; Fig. 9: 1–3. Holotype Specimen WAM 18.3/M10-23 (Fig. 4: 9, 12).
Type sample (& lithostrat): Sample BMR 95/DR7/8
Type age (chronostrat): early Bajocian based on nannoplankton
Type locality: dredged at a water depth of 4530 to 3900m on the northeastern wall of Mermaid Canyon offshore of northwestern Australia; the dredge haul start- ing at 16◦ 18.9′ S, 118◦ 22.2′ E and ending at 16◦ 18.2′ S, 118◦ 24.3′ E.

Current identification:


Original Description

Diagnosis: Test calcareous, a medium–high globigerinid trochospire, rapidly expanding, with an H/D ratio of approximately 1 : 1. Coil of usually two whorls, the final whorl containing three to rarely 3.5 spherical chambers. Aperture a very high arch, almost loop-shaped or virguline, with a prominent lip; aperture umbilical or slightly extraumbilical in position. Wall structure microperforate, with prominent pseudomuricae, showing a sequence of development on different chambers by secondary lamination.

Description; Trochospirally coiled test with a rapidly expanding spire of usually two whorls, the H/D ratio approximating 1 : 1. The proloculus on the holotype and most specimens is prominent at the base, visible below four to five chambers in the first whorl and three in the subsequent whorl (Fig. 4: 9). One paratype (WAM 18.4/M55-27) has a flattened first whorl but this is not typical (Fig. 4: 11). Heavy secondary lamination often obscures the chambers in the first whorl. The second and usually final whorl consists of three hemispherical chambers. The sutures are depressed, their shape at depth modified by wall ornament. The aperture is umbilical, a narrow, very high arch, about 10μm wide, asymmetrical, almost loopshaped, rising one-third to halfway up the face of the final chamber. The aperture is rimmed by a narrow lip ornamented by tubercules from the top of the arch down to the outer margin (Fig. 4: 4, 6, 12). The inner margin of the apertural lip (i.e. the margin closest to the axis of coiling) is smooth and turns outwards in a curved, plate-like extension of the lip, forming a buttress-like structure where the lip attaches to the previous whorl (Fig. 4: 1, 4, 6, 9; Fig. 6: 1). The final chamber or bulla is broken away in almost all specimens. Paratype WAM 18.6/M86-6 has the final chamber broken off but a well-preserved aperture on the penultimate chamber (Fig. 4: 4–6). Paratype WAM 18.5/M73-14 appears to have had a terminal bulla, as the scar of attachment occupies a central position above the last three chambers (Fig. 4: 2; Fig. 7: 5). A small remnant of very thin, single-layered wall is attached to the apertural margin of the previous chamber (Fig. 4: 3); this remnant (arrowed) is interpreted to be part of the bulla.

Wall structure: Each chamber wall consists of inner lamella approximately 2μm thick, coating the floor of the chamber and the new wall, and microperforate outer lamella approximately 3– 4μm thick (Fig. 6: 3; Fig. 9: 3). A gap between these lamellae has been suggested to consist of an organic matrix which likely corresponds to the primary organic membrane (Aleksey Sadekov, personal communication, 2019). A chamber-by-chamber photographic analysis shows that on the youngest chamber, pseudomuricae are scattered and low, and the chamber surface is microperforate with pores
Wall composition: Raman spectroscopy results on G. altissapertura from sample BMR 95/DR7/8, performed by Aleksey Sadekov of the University of Western Australia, indicate that the wall composition of this species is aragonite, with a high organic content.

Size:
Height 0.13 - 0.22 mm; diameter 0.13 - 0.21 mm (range of 10 specimens detailed in table 2)

Etymology:
Describing the high aperture.

Extra details from original publication
Remarks: This form is distinguished from Globuligerina bathoniana australiana by the narrow very high aperture and the rapidly expanding trochoid test usually of two whorls. Although it has been indicated in the literature (Gradstein et al., 2017a) that the aperture is a variable and transitional feature in G. bathoniana, in photographed specimens of the present material it has been possible to consistently assign specimens to either G. altissapertura n. sp. or to G. bathoniana australiana n. ssp. using the aperture. Pazdrowa (1969) in her original description of Globuligerina bathoniana stated that high and narrow apertures were “rare”, not “normal”. In her material “The presence of passage forms does not permit the establishment of separate systematic units” (Pazdrowa, 1969, p. 51), whereas in the present material, the rare narrow apertures become frequent in the population, and the form can be distinguished from G. bathoniana australiana n. ssp. G. altissapertura, with its rapidly expanding medium–high spire, is not conspecific with the low-spired G. oxfordiana (Grigelis), which was recently redescribed (Grigelis, 2016). Statements that G. oxfordiana includes forms with only three chambers in the last whorl are not supported by type specimens or by illustrations of topotype material (see Grigelis, 2016, and Gradstein et al., 2017a). Due to the much higher spire of G. altissapertura and fewer chambers in the last whorl (three versus four in G. oxfordiana), as well as the very high aperture, it seems necessary to give these medium– high-spired Australian forms with a high-arched, “virguline-shaped” aperture a new name.

Editors' Notes

References:

Apthorpe, M. (2020). Middle Jurassic (Bajocian) planktonic foraminifera from the northwest Australian margin. Journal of Micropalaeontology. 39: 93-115. gs V O


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Globuligerina altissapertura compiled by the pforams@mikrotax project team viewed: 3-12-2022

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