Rotorbis Sellier de Civrieux 1977

Mamo, Briony L., 2016, Benthic Foraminifera from the Capricorn Group, Great Barrier Reef, Australia, Zootaxa 4215 (1), pp. 1-123 : 82

Rotorbis Sellier de Civrieux 1977

Rotorbis sp. cf. R. auberii ( d'Orbigny 1839) ( Fig. 19 :14–16)

Description. Test trochospiral, planoconvex to biconvex, with crescentic shaped chambers on spiral side and curved subtriangular chambers on umbilical side. Test outline sub-circular with pinched, keeled, peripheral margin. Keel flattened with rounded edge, varying slightly in size. Coarse, unevenly spaced perforations on chambers of spiral and umbilical sides. Perforations tend to be more numerous and closely packed on umbilical side, but are absent adjacent to umbilicus and posterior part of chamber. Perforations on spiral side tend to trace sutures. Sutures flush or weakly depressed on spiral side. Sutures on umbilical side deep, strongly curved, radiating, increasing in length with each chamber and lined with fine, papillate ornament.

Remarks. All of the available specimens are damaged making an accurate identification difficult. However, the distinct arrangement of the umbilical sutures, test chamber shape and arrangement indicate a close comparison with R. auberii ( Fig. 19 :14–16).

Specimens of R. auberii described by Loeblich & Tappan (1994) are similar to those collected from the CG especially in test shape and chamber arrangement, but lack any kind of keel. The perforate ornament on the spiral side is clustered around the peripheral areas of the test. Some perforations are scattered along the sutures, but the central test area is largely imperforate. On the umbilical side, the perforations are far fewer and cluster more exclusively around the posterior test area with papillae lining the deep umbilical sutures ( Loeblich & Tappan 1994). Specimens tentatively assigned to R. auberii by Parker (2009) and Debenay (2012) closely resemble Rotorbis sp. cf. R. auberii from the CG. All taxa possess a slight keel and the perforate ornament is similarly arranged on both test sides. It is likely that the CG specimens are conspecific with those illustrated by Parker (2009, fig. 513a–h) and Debenay (2012, pg. 212) despite their damaged condition. Parker (2009) noted discrepancies in the perforate arrangement and the structure of the folium when compared to the type specimen of R. auberii .

The original specimens of R. auberii described by d’Orbigny (1839) were collected from Cuba and Loeblich & Tappan’s (1994) specimens of R. auberii came from a depth of 44 m from the southeast Timor Sea and at 24 m depth from north of Bathurst and Melville Islands, eastern Timor Sea . Haig (1997) mentioned specimens amongst his collections from the Exmouth Gulf of Western Australia, but the specimens were not illustrated. Parker’s (2009) specimens were collected from Ningaloo Reef , Western Australia and Debenay’s (2012) from the southwestern lagoon of New Caledonia from depths less than 40 m.

Distribution within study area. Rotorbis sp. cf. R. auberii was most abundant in Wistari and One Tree Reefs with an average abundance of four to five specimens per site, with the maximum at site 34 in One Tree Lagoon with twelve specimens collected. This taxon was rarely collected from Heron Reef and was absent from Sykes Reef and the channel sample. Several specimens of R. auberii were live at the time of collection from One Tree Reef and Heron Reef flat, but never more than one live specimen per site.

Figures

FIGURE 19. (Unless otherwise specified all scale bars = 100 µm). 1 – 2. Uvigerina cf. U. porrecta Brady, 1879, QM # G 465988 from OTI 51. Scale bar = 50 µm. 1. Lateral view. 2. Oral view. 3 – 4. Trifarina pacifica (Albani, 1974), QM # G 465989 from OTI 51. Scale bar = 50 µm. 3. Lateral view. 4. Oral view. 5 – 6. Fijiella simplex (Cushman, 1929), QM # G 465828 from OTI 39. 5. Lateral view. 6. Oral view. 7 – 10. Eponides cf. E. repandus (Fichtel & Moll, 1798), 7. QM # G 465880 from CHANNEL, scale bar = 200 µm. 7. Spiral view. 8. Peripheral view. 9. QM # G 465881 from CHANNEL, umbilical view. Scale bar = 500 µm. 10. QM # G 465872 from CHANNEL, umbilical view. Scale bar = 200 µm. 11 – 13. Orbitina parri Collins, 1974, QM # G 466000 from OTI 47. Scale bar = 50 µm 11. Spiral view. 1 2. Umbilical view. 13. Peripheral view. 1 4 – 16. Rotorbis cf. R auberii (d’Orbigny, 1839). 1 4. QM # G 465914 from OTI 53 spiral view, scale bar = 50 µm. 1 5 – 16. QM # G 465915, umbilical view (15) peripheral view (16), scale bar for 16 = 50 µm. 1 7 – 21. Neoconorbina sp. 1. 17 – 18. QM # G 466138 from ST / HW 8, spiral (17) and peripheral (18) views. Scale bar = 50 µm. 19 – 21. QM # G 466008 from OTI 47, spiral (19), peripheral (20) and umbilical (21) views. Scale bar for 19 and 20 = 50 µm.