Millettiana Banner Pereira & Desai 1985

Mamo, Briony L., 2016, Benthic Foraminifera from the Capricorn Group, Great Barrier Reef, Australia, Zootaxa 4215 (1), pp. 1-123 : 93

Millettiana Banner Pereira & Desai 1985

Millettiana milletti ( Heron-Allen & Earland 1915) ( Fig. 22 :7–17)

1903 Cymbalopora bulloides Milletti , p. 697, pl. 7, fig. 4.

1915 Cymbalopora milletti Heron-Allen & Earland , p. 689, pl. 51, figs 32–35.

1915 Cymbalopora milletti Heron-Allen & Earland ; Heron-Allen, p. 253, pl. 16, fig. 36; pl. 17, figs 46–8, 50–51. 1915 Cymbalopora tabellaeformis Brady ; Heron-Allen, p. 258, pl. 17, fig. 54.

1985 Millettiana milletti (Heron-Allen & Earland) ; Banner et al., p. 170, pl. 4, figs 1–10; pl. 6, fig. 4. 1987 Millettiana milletti (Heron-Allen & Earland) ; Loeblich & Tappan, p. 591, pl. 648, figs 7–11. 1994 Millettiana milletti (Heron-Allen & Earland) ; Loeblich & Tappan, p. 153, pl. 329, figs 1–12. 2009 Millettiana milletti (Heron-Allen & Earland) ; Parker, p. 640, figs 452a–k, 453a–g. 2012 Millettiana milletti (Heron-Allen & Earland) ; Debenay, p. 244, pl. 22.

Description. See Banner et al. (1985, p. 170, pl. 4, figs 1–10; pl. 6, fig. 4), Loeblich & Tappan (1987, p. 591, pl. 648, figs 7–11) and Parker (2009, p. 640, figs 452a–k, 453a–g).

Remarks. Millettiana milletti ( Heron-Allen & Earland 1915) is characterised by a trochospiral, planoconvex test bearing crescentic, coarsely perforate chambers on the spiral side. The chambers on the umbilical side are mushroom shaped and are either imperforate or have a few clustered perforations ( Fig. 22 :7–17).

The unusual mushroom shaped umbilical chambers can be used to distinguish this species from the similar Cylamboporetta species, such as C. bradyi , especially in juvenile specimens. Adult specimens of Cymbaloporetta do not have limbate sutures on the spiral side, however the intraspecific variety of how distinct the sutures are can make this difficult to identify (compare Fig. 22 :7, 11, 14 & 16).

Most specimens of M. milletti from the CG were not found during the planktonic stage (only one such specimen was collected) which occurs immediately prior to and during gametogenesis (Heron-Allen 1915). Most of the collected material represents benthic or juvenile attached specimens. The attached juvenile specimens were all live specimens, but cannot be identified with 100% confidence since the umbilical side of the test is invariably obscured. However, the test profile appears consistent and has the same outline of the underlying mushroomshaped umbilical chambers and the spiral side chambers bear the limbate sutures diagnostic of this taxon. The presence of these two distinctive features serves to distinguish these juvenile specimens from Cymbaloporetta and supports assignment to M. milletti . Juvenile specimens collected from the CG appear to gradually develop coarse perforations on the spiral test side, whose distribution and number increase during ontogeny. Heron-Allen (1915) encountered juvenile attached specimens that appear very similar to the specimesn of M. milletti from the GBR, but he assigned them C. tabellaeformis . Heron-Allen’s (1915, pl. 17, fig. 54 non pl. 18, fig. 55) attached specimens lack the deep periphery typical of C. tabellaeformis and also appear to have raised imperforate spiral side sutures that are diagnostic of M. milletti .

Millettiana milletti was the most abundant taxon collected as live from the CG, probably the result of the high incidence of attached juvenile specimens collected. These attached juvenile stages have not been previously discussed in detail, and is likely the result of their small size and slightly cryptic nature when they are commonly attached to reef rubble.

The specimens of M. milletti documented by Millett (1903) were from the Malaysian Archipelago and later specimens described by Heron-Allen & Earland (1915) and Heron-Allen (1915) come from Mozambique in the Kerimba Archipelago. Heron-Allen (1915) noted numerous specimens of M. milletti collected by Murray in 1875 from Honolulu, Hawaii . Banner et a l. (1985) collected specimens from near the type locality off Mozambique, offshore from Mombasa, Kenya and, like specimens collected from the CG, these often lacked the planktonic chamber. Loeblich & Tappan (1987; 1994) re-illustrated the Mombasa specimens of Banner et al. (1985) and reported M. milletti from depths of 87–95 m from the Western Timor Sea. Parker (2009) reported specimens from Ningaloo Reef , Western Australia and found significant numbers of both planktonic and benthic stage specimens and Debenay (2012) collected specimens from the southwestern lagoon of New Caleondia (40 m).

Distribution within study area. Millettiana milletti was collected from all sampled reefs and with a maximum abundance of 26 specimens found at site 50 in One Tree Lagoon 2. However, it is only in One Tree Lagoons that an abundance of more than ten specimens per site was recorded. Millettiana milletti was the most abundant live species collected from the CG. Sites with the highest number of live specimens collected included site 50 in One Tree Lagoon 2 and site 41 in Heron Lagoon.

Figures

FIGURE 22. (Unless otherwise specified all scale bars = 100 µm). 1 – 4. Cymbaloporetta sp. 1. 1 – 2. QM # G 465969 from OTI 45 peripheral (1) and umbilical (2) views. 3 – 4. QM # G 465971 from OTI 48 peripheral (3) and umbilical (4) views. 5 – 6. Cymbaloporetta? sp. 1, QM # G 466024 from T 1 – 4. Spiral view (5) and close-up spiral view (6). Scale bar for 5 = 200 µm. Scale bar for 6 = 20 µm. 7 – 17. Millettiana milletti (Heron-Allen & Earland, 1915). 7. QM # G 465789 from ST / HW 2, spiral view. 8 – 9. QM # G 465788 from ST / HW 2, peripheral (8) and umbilical (9) views. 10 – 12. QM # G 466032 from ST / HW 8, spiral (10) close-up spiral (11) and peripheral (12) views. Scale bar for 10 = 200 µm. Scale bar for 11 = 50 µm. Scale bar for 12 = 20 µm. 13 – 14. QM # G 466027 from T 1 – 2 spiral (13) and peripheral (14) views. Scale bar for 14 = 50 µm. 15. QM # G 466140 from OTI 50, umbilical view. Scale bar = 50 µm. 16 – 17. QM # G 466088 from OTI 50 spiral (16) and peripheral (17) views. Scale bar for 17 = 50 µm. 1 8 – 20. Acervulina mabahethi (Said, 1949). 18 – 20. QM # G 466003 from OTI 53 spiral (7), umbilical (8) and peripheral (20) views.