Benthic Foraminifera from the Capricorn Group, Great Barrier Reef, Australia Author Mamo, Briony L. text Zootaxa 2016 4215 1 1 123 journal article 37169 10.11646/zootaxa.4215.1.1 0087fa4c-a4f0-45d9-a2de-d433d7885753 1175-5326 272923 B91D1782-C11A-4CDC-96B6-76104FEE51BD Heterostegina d’Orbigny 1826 Heterostegina depressa d’Orbigny 1826 ( Fig. 25 :16, 17) 1826 Heterostegina depressa d’Orbigny , p. 305, pl. 17, figs 5–7. 1965 Heterostegina sp.; Jell et al ., p. 273, pl. 44, fig. 8. 1984 Heterostegina depressa d’Orbigny ; Hallock, p. 251, fig. 1: 9. 1991 Heterostegina depressa d’Orbigny ; Van Marle, p. 195, pl. 21, fig. 4. 1992a Heterostegina depressa d’Orbigny ; Hatta & Ujiié, p. 204, pl. 50, fig. 4. 1993 Heterostegina depressa d’Orbigny ; Hottinger et al ., p. 157, pl. 228, figs 1–11; pl. 229, figs 1–8, pl. 230, fig. 9. 1994 Heterostegina depressa d’Orbigny ; Loeblich & Tappan, p. 171, pl. 389, figs 1–6; pl. 390, figs 1–3. 1999 Heterostegina depressa d’Orbigny ; Harney et al., p. 64, fig. 1. 1999 Heterostegina depressa d’Orbigny ; Hohenegger et al ., p. 157, fig. 30. 2002 Heterostegina depressa d’Orbigny ; Yordanova & Hohenegger, p. 201, pl. 34, figs 7–11. 2004 Heterostegina depressa d’Orbigny ; Saraswati et al ., p. 340, pl. 1, fig. 6. 2009 Heterostegina depressa d’Orbigny ; Parker, p. 625, fig. 443a–j. 2012 Heterostegina depressa d’Orbigny ; Debeny, p. 222, pl. 20. Description. See Hohenegger et al . (1999 , p. 157, fig. 30); Hottinger et al . (1993 , p. 157, pl. 228, figs 1–11; pl. 229, figs 1–8, pl. 230, fig. 9); Van Marle (1991 , p. 195, pl. 21, fig. 4) and Yordanova & Hohenegger (2002, p. 201, pl. 34, figs 7–11) . Remarks. Heterostegina depressa d’Orbigny 1826 has a large, smooth, lamellar, planispiral, compressed and involute test. The chambers become semi-involute and flat as the test grows and the chamberlets are divided by imperforate, slightly raised sutures. Interiosutural areas are finely perforate and the aperture is an arched slit at the base of the apertural face ( Fig. 25 :16, 17). Röttger & Hallock (1982) and Van Marle (1991) noted that H . depressa displays strong variation in size and the arrangement of the honeycomb-like rectangular chamberlets that develop across the flattened, outermost part of the test. Inspection of specimens collected by Brady (1884) during the Challenger expedition on legs 172 and 219A show this variation and an affinity with CG specimens. Specimens from leg 172, collected off Tongatobu Friendly Islands from a depth of 33 m (British NHM reg. no. ZF1575) appeared almost identical to those collected from the CG. Yet specimens from leg 219A collected from the Admiralty Islands at a depth of 31 m (British NHM reg. no. ZF1576) had some specimens identical to CG specimens and others with differing size and breadth in chamber arrangement. Some specimens from Admiralty Island possessed broad, square-shaped chambers, whilst the chamber arrangement of other specimens was so narrow and compressed that the chambers appeared as tightlypacked rectangles. Initial descriptions reported H . depressa as a key tropical to subtropical species that increased in size with increasing water depth and inhabited warm, clear, quiet marine waters in carbonate-rich sediments with limiting factors including light intensity and energy levels ( Röttger 1976 ; Hottinger 1977 ; Hallock 1984 ; Crouch & Poag 1987 ). Heterostegina depressa has a global distribution and is abundant throughout the Indo-Pacific region (Heron Island—Jell et al . 1965; Hawaiian and Western Caroline Islands—Röttger & Hallock 1982 , Hallock 1984 , Harney 1999 ; Ryukyu Island Arc—Van Marle 1991 , Hatta & Ujiié 1992a , Hohenegger et al ., 1999 , Yordanova & Hohenegger 2002 , Saraswati et al . 2004 ; Gulf of Aqaba—Hottinger et al . 1993; Timor Sea—Loeblich & Tappan 1994 ; Ningaloo Reef—Parker 2009; New Caledonia between 15–50 m—Debenay 2012). Distribution within study area. Across the CG there is a distinct preference by H . depressa for comparatively deeper water environments (~ 35 m depth) with forty of the fifty collected specimens from the channel sample between Heron and Wistari Reefs. This distribution pattern conforms with the known distribution of H . depressa in terms of depth ( Loeblich & Tappan 1994 ) and quiet energy regimes within the photic zone ( Van Marle 1991 ).