Abditodentrix Patterson 1985

Mamo, Briony L., 2016, Benthic Foraminifera from the Capricorn Group, Great Barrier Reef, Australia, Zootaxa 4215 (1), pp. 1-123 : 74-75

Abditodentrix Patterson 1985

Abditodentrix rhomboidalis ( Millett 1899) ( Fig. 18 :1–3)

1899 Textularia rhomboidalis Millett , p. 559, pl. 7, fig. 4.

1992a Brizalina ? rhomboidalis (Millett) ; Hatta & Ujiié, p. 172, pl. 26, fig. 2. 1993 “ Bolivinita ” rhomboidalis (Millett) ; Haig, p. 171, pl. 6, figs 14–16.

1994 Tortoplectinella rhomboidalis (Millett) ; Loeblich & Tappan, p. 113, pl. 216, figs 1–6. 2002 Tortoplectinella rhomboidalis (Millett) ; Bicchi et al., p. 282, fig. 7:18.

2000 Abditodentrix rhomboidalis (Millett) ; Revets, p. 371, pl. 2, fig. 44. 2009 Abditodentrix rhomboidalis (Millett) ; Parker, p. 427, fig. 308a– i. 2012 Abditodentrix rhomboidalis (Millett) ; Debenay, p. 170, pl. 12.

Description. See Millett (1899, p. 559, pl. 7, fig. 4) and Parker (2009, p. 427, fig. 308a–i).

Remarks. Abditodentix rhomboidalis ( Millett 1899) is characterised by a biserial chamber arrangement, subquadrilateral cross section, and flattened, perforate test walls. The perforations are particularly well developed on the final chambers and around the sutures of the initial chambers. The top of the final chambers are ornamented by a thickened test wall that has a meandering crenulated pattern and the sutures are raised and thickened. The aperture consists of a basal loop shape with a lip that only borders one side of the aperture and folds around to become a tooth plate that extends down the centre of the aperture ( Fig. 18 :1–3).

Despite placement in various genera, this species is placed in Abditodentrix due to its truncated margins and aperture possessing a lip that only partially extends around the apertural margin ( Patterson 1985; Parker 2009). The only difference between the CG specimens and other published examples of this taxon, is the less pronounced twisting of the final chambers ( Hatta & Ujiié 1992a; Loeblich & Tappan 1994; Parker 2009).

Millett (1899) documented specimens collected from various areas of the Malaysian Archipelago. Hatta & Ujiié (1992a) found this species between Ishigaki and Iriomote Islands within the Ryukyu Island Arc as a common element of the biota. Loeblich & Tappan (1994) only collected A. rhomboidalis from depths of 93–95 m from the Western Timor Sea and at 1158 m depth in the northern Timor Trough, Leti Strait. Haig (1993) collected specimens predominantly from the back reef flat and lagoon basin of the Papuan Lagoon and discovered that the species preferred depths ranging from 0–30 m and was more abundant in sediments with very little (0–5%) or significant mud content (85–100%). Revets (2000) collected A. rhomboidalis in low abundance from a single, shallow, estuarine lagoon locality in Leschenault Inlet, south Western Australia, close to the estuary mouth to open waters. Bicchi et al. (2002) collected this species from atoll lagoons from the central Tuamoto Archipelago, Parker (2009) from Ningaloo Reef , Western Australia and Debenay (2012) from the Bay of Prony (10–30 m) and coastal bay (5– 10 m) of New Caledonia .

Distribution within study area. Abditodentrix rhomboidalis only occurred in small numbers (one to five specimens per site) in lagoon and reef flat samples of the CG. However, abundance is greatly increased in the channel sample with thirty specimens from a single site. This distribution matches other documented occurrences of this species which is known to favour deeper water environments compared to shallower reef flat and lagoon settings.

Figures

FIGURE 18. (Unless otherwise specified all scale bars = 100 µm). 1 – 3. Abditodentrix rhomboidalis (Millett, 1899), scale bar = 50 µm. 1 – 2. QM # G 465946 from OTI 43, lateral (1) and oral (2) views. 3. QM # G 465932 from OTI 1, lateral view. 4 – 9. Bolivina variabilis (Williamson, 1858). 4 – 5. QM # G 466137 from OTI 43, scale bar = 50 µm, lateral (4) and oral (5) views. 6 – 7. QM # G 465933 from OTI 8, lateral (6) and oral (7) views. Scale bar for 7 = 200 µm. 8 – 9. QM # G 465935 from OTI 8, lateral (8) and oral (9) views. 10 – 11. Sagrinella jugosa (Brady, 1884), QM # G 465975 from OTI 47. Scale bar = 50 µm 10. Lateral view. 11. Oral view. 12 – 13. Rugobolivinella elegans (Parr, 1932), QM # G 465941 from OTI 20. 12. Lateral view. 13. Oral view. 14 – 15. Loxostomina limbata (Brady, 1884), QM # G 465829 from OTI 39. 14. Lateral view. 15. Oral view. 16 – 17. Favocassidulina favus (Brady, 1877), QM # G 465948 from OTI 47. Scale bar = 50 µm. 16. Spiral view. 17. Umbilical view. 18 – 19. Globocassidulina bisecta Nomura, 1983, QM # G 466001 from OTI 47. Scale bar = 50 µm. 18. Lateral view. 19. Oral view. 20 – 21. Siphogenerina raphana (Parker & Jones, 1865), QM # G 465787 from ST / HW 2. 20. Lateral view, scale bar = 200 µm. 21. Oral view.