Spiroloculina d’Orbigny 1826

Mamo, Briony L., 2016, Benthic Foraminifera from the Capricorn Group, Great Barrier Reef, Australia, Zootaxa 4215 (1), pp. 1-123 : 27-29

Spiroloculina d’Orbigny 1826

Spiroloculina angulata Cushman 1917 ( Fig. 6 :14–17)

1917 Spiroloculina grata Terquem var. angulata Cushman , p. 36, pl. 7, fig. 5. 1988 Spirolculina angulata Cushman ; Haig, p. 234, pl. 10, figs 1–7.

1993 Spriloculina cf. S. angulata Cushman ; Hottinger et al. p. 44, pl. 24, figs 11–14. 1995 Spiroloculina angulata Cushman ; Lobegeier, p. 68, pl. 1, fig. 5.

1997 Spiroloculina angulata Cushman ; Haig, p. 273, fig. 4: 22.

Description. See Cushman (1917, p. 36, pl. 7, fig. 5) and Hottinger et al. (1993, p. 44, pl. 24, figs 11–14).

Remarks. These specimens were assigned to Spiroloculina angulata Cushman 1917 because of the angular spiroloculine-arranged chambers with broadly spaced, sinuous, discontinuous striae that trace the exterior walls.

Whilst the original description of this species by Cushman (1917, p. 36) closely matches the material collected from the CG, the same cannot be said of the illustrations associated with the description ( Cushman 1917, pl. 7, fig. 5a, b). Cushman’s (1917, pl. 7, fig. 5a, b) illustrated material of S. angulata show specimens with numerous, distinct, closely spaced striae sometimes so pronounced that the chamber peripheries are carinate. Cushman (1917) does indicate that he regarded these morphologies as unusual. Subsequent illustrations of S. angulata ( Haig 1988; Hottinger et al. 1993; Lobegeier 1995; Haig 1997) closely resemble the CG specimens and show specimens with striae that are more weakly defined, less numerous, spaced further apart and are far less constant in the way they trace the chamber’s exterior.

Spiroloculina angulata can be easily discriminated from other collected CG Spiroloculina species by its anastomising striate ornament. It most closely resembles Spiroloculina corrugata Cushman & Todd 1921 ( Fig. 6 :18, 19), but the striate ornament of S. corrugata is more numerous, defined and regular. The ornament, in combination with a more compressed test and less oblique sutures, give the exterior chambers a more quadrate-like shape in cross-section.

Haig’s (1988; 1997) specimens of S. angulata from the Papuan Lagoon and Exmouth Gulf closely resemble those collected from the CG, particularly in regards to ornament. They differ only in that some specimens from the Papuan Lagoon have teeth with thickened tips ( Haig 1988, pl. 10, figs 1–7) whereas the CG specimens only have a simple or bifurcate, short tooth ( Fig. 6 :17). Hottinger et al. (1993) only tentatively assigned specimens to S. angulata due to the lack of a strong, distinct carina illustrated by Cushman (1917, pl. 7, fig. 5). However, Cushman (1917) noted that this morphotype was an extreme variant and so the Hottinger et al. (1993) attribution to S. angulata is probably correct. The specimens illustrated by Hottinger et al. (1993, pl. 24, figs 11–14) showed tests with more abundant striae, yet their weak, discontinuous, wandering style remains the same. Hottinger et al. (1993) mention that specimens have a distinct anvil-shaped, bifid dentition which is not apparent in Cushman’s (1917) or Haig’s (1988; 1997) illustrations nor in the CG specimens. The anvil-shape style of dentition does resemble the thickened tip dentition of Papuan Lagoon specimens ( Haig, 1988) and may be a more developed form of this tooth. Lobegeier (1995) also reported this species from the Low Isles, central GBR and the illustrated material has the same ornament as the specimens described by Haig (1988; 1997) and the CG specimens as well as a tooth with a thickened tip similar to specimens illustrated by Haig (1988) and Hottinger et al. (1993).

Distribution within study area. Spiroloculina angulata was the most abundant spiroloculine species collected from the CG. The site with the greatest abundance was site 36 in One Tree Lagoon 1, but occurred in relatively low abundance (zero to four specimens per site) on Heron Reef flat except along Transect 3 which extends east from Heron Island into Heron Lagoon. This species was absent from Sykes Reef.

Spiroloculina corrugata Cushman & Todd 1944 ( Fig. 6 :18, 19)

1924 Spiroloculina antillarum d’Orbigny ; Cushman, p. 55, pl. 20, fig. 1.

1944 Spiroloculina corrugata Cushman & Todd , p. 51, pl. 8, figs 22–25.

1968 Spiroloculina corrugata Cushman & Todd ; Matsunaga, p. 134, pl. 29, fig. 7. 1971 Spiroloculina antillarum d’Orbigny ; Bock et al., p. 13, pl. 3, fig. 7.

1992b Spiroloculina corrugata Cushman & Todd ; Hatta & Ujiié, p. 64, pl. 5, fig. 5. 1993 Spiroloculina corrugata Cushman & Todd ; Hottinger et al., p. 46, pl. 26, figs 5–9. 1994 Spiroloculina corrugata Cushman & Todd ; Lobelich and Tappan, p. 43, pl. 65, fig. 4–7. 1995 Spiroloculina corrugata Cushman & Todd ; Lobegeier, p. 68, pl. 1, figs 7–10. 1995 Spiroloculina antillarum d’Orbigny ; Yassini & Jones, p. 81, figs 141, 145, 146. 1999 Spiroloculina antillarum d’Orbigny ; Hayward et al., p. 107, pl. 6, figs 4, 5. 2012 Spiroloculina antillarum d’Orbigny ; Debenay, p. 132, pl. 5.

Description. See Bock et al. (1971, p. 13, pl. 3, fig. 7), Cushman & Todd (1944, p. 51, pl. 8, figs 22–25) and Hottinger et al. (1993, p. 46, pl. 26, figs 5–9).

Remarks. This taxon is characterised by a spiroloculine chamber arrangement and multiple, fine, well defined longitudinal costae that extend the length of the test. The test is also slightly depressed in the centre with distinct, depressed sutures and a terminal aperture situated on a well-developed neck that is as wide as the aperture ( Fig. 6 :18, 19).

Much confusion exists, which is evident in the synonymy, concerning the taxonomic status of this species. Cushman & Todd (1944) note that S. corrugata has a much larger, relatively thinner test than S. antillarum and also posseses more numerous and finer costae. Comparison of S. corrugata to d’Orbigny’s (1839, pl. 9, figs 3, 4) original illustrations of S. antillarum and Le Calvez’s (1977, pl. 17, fig. 3, 5) micrograph of the S. antillarum lectotype and reproduced illustrations, show that S. antillarum is greatly compressed at its centre, so much so that in cross-section, the test appears to flare from the centre to the periphery and the aperture is proportionally smaller.

These differences are less profound in Le Calvez’s (1977, pl. 17, figs 1, 2, 6) topotype images in their revision of d’Orbigny’s (1839) collection. Spiroloculina corrugata is only very slightly compressed in the centre and the aperture is the same width as the peripheral chamber from which it extends. Parker (2009) synonymised the Cushman & Todd (1944) holotypes under S. antillarum due to their similarities but mentions the large variety of morphotypes within the species. Illustrated specimens of S. antillarum from Ningaloo Reef possess fewer and more broadly spaced costae than the S. corrugata specimens from the CG. Specimens of both S. corrugata and S. antillarum illustrated by Debenay (2012) show how similar the species are as they seem to possess attributes used to define both species. Debenay’s (2012) S. corrugata illustrates both broad and elongate test shapes and possesses more numerous and finer costae that are discontinuous compared to S. antillarum . Yet in transverse section S. corrugata ’s chambers are strongly convex and U-shaped while S. antillarum chambers are nearly circular, opposite to Cushman & Todd’s (1944) original description of only a slightly compressed test for S. corrugata and stronger compression for S. antillarum . Debenay’s (2012) specimens of S. corrugata bear the additional defining characteristic of a peristomal rim surrounding their terminal apertures, a feature found in some ( Hottinger et al. 1993; Loeblich & Tappan 1994) but not other occurrences of S. corrugata ( Matsunaga 1963; Hatta & Ujiié 1992b; Lobegeier 1995).

The heavily costate ornament of S. corrugata serves to discriminate this species from other spiroloculine taxa collected from the CG. The only species closely resembling S. corrugata is S. angulata , but this taxon has fewer, more weakly developed and widely spaced costae that meander and are discontinuous. The periphery of S. angulata is also more angled and sharp ( Cushman & Todd 1944).

Specimens collected by Matsunaga (1963) bear strong similarity to CG specimens whilst those collected by Hottinger et al. (1993) have more numerous costae that twist slightly around the periphery. This twisting is not observed in other synonymised specimens discussed above ( Bock et al. 1971; Hatta & Ujiié 1992b; Hayward et al. 1999). Loeblich & Tappan (1994, pl. 65, figs 4–7) further illustrate the morphological variety of S. corrugata with a more elongate and slender test and a narrower aperture.

Spiroloculina corrugata was originally published as S. antillarum by Cushman (1924) from the Samoan Islands including Pago Pago Harbour and Aua Reef. It has been found in depths ranging from 0–292 m ( Cushman 1924; Cushman & Todd 1944; Loeblich & Tappan 1994; Debenay 2012) globally ( Anima Sola Island , Philippines—Cushman & Todd 1944; northern Japan—Matsunaga 1963; Florida Bay—Bock et al. 1971; Ryukyu Island Arc—Hatta & Ujiié 1992b; Gulf of Aqaba—Hottinger et al. 1993; central Timor Sea—Loeblich & Tappan 1994; Low Isles , GBR—Lobegeier 1995; southeastern coast of Australia—Yassini & Jones 1995; Kermadec Islands , New Zealand—Hayward et al., 1999; New Caledonia – Debenay 2012).

Distribution within study area. Spiroloculina corrugata was the second most abundant Spiroloculina species collected from the CG and has a similar distribution and abundance to S. angulata .

Figures

FIGURE 6. (Unless otherwise specified all scale bars = 100 µm). 1 – 7. Adelosina carinatastriata Wiesner, 1923. 1 – 2. QM # G 466097 from WL 21, lateral view (1) and oral (2) views. 3 – 5. QM # G 465820 from OTI 36, lateral (3), peripheral (4) and oral views (5). 6 – 7. QM # G 465919 from WL 7, lateral (6) and oral (7) views. 8 – 13. Adelosina cf. A. pulchella (d’Orbigny, 1826). 8 – 10. QM # G 466087 from ST / HW 10 lateral view (8), oral view (9) and peripheral view (10). 11 – 13. QM # G 466067 from HL 40 lateral views (11, 12) and oral view (13). 14 – 17. Spiroloculina angulata Cushman, 1917. 14 – 15. QM # G 465824 from OTI 36 lateral view (14) and oral view (15). Scale bars = 50 µm. 16 – 17. QM # G 466066 from T 3 – 6 lateral (16) and oral (17) views. 18 – 19. Spiroloculina corrugata Cushman & Todd 1944, QM # G 466059 from OTI 39. 18. Lateral view. 19. Peripheral view. 20 – 21. Spiroloculina cf. S. depressa d’Orbigny, 1826, QM # G 465893 from ST / HW 8. 20. Lateral view 21. Oral view.