Anoteropora latirostris Silén, 1947

(Fig. 14.1–4)

Anoteropora latirostris Silén, 1947: 58, text-figs 49–50, pl. 5, figs 25–27; Cook 1966: 210; Cook & Chimonides 1994b: 54, figs 1c, 2e–f; Jacob et al. 2019: 9, figs 1–6; Martha et al. 2020: fig. 11.40A–B; Di Martino 2023: 88, figs 48, 49.

Anoteropora magnicapitata: Balavoine 1959: 278, pl. VI, fig. 2, non Anoteropora magnicapitata Canu & Bassler, 1927.

Material examined. SMF 40788 (St. 283 KU; Fig. 14.3–4), SMF 60000 (St. 283 KU), SMF 60001 (St. 283 KU), SMF 60002 (St. 283 KU; Fig. 14.1), SMF 60003 (St. 283 KU), SMF 60004 (St. 236 KD), SMF 60005 (St. 283 KU), SMF 60006 (St. 283 KU), SMF 60007 (St. 283 KU), SMF 60008 (St. 283 KU), SMF 60009 (St. 283 KU; Fig. 14.2).

Description. Colony discoidal, cup-shaped, convex frontally, concave on the basal side, multiserial, unilamellar (Fig. 14.1). Autozooids arranged in regular rows radiating from the centrally located ancestrula, opening on the convex surface (Fig. 14.2). Basal side divided into hexagonal sectors, bearing numerous depressions, each having a small, circular pore at the centre. Ancestrula located in colony centre, circular, broken in observed specimens, surrounded by six autozooids.

Autozooids hexagonal, separated by thin furrows, 380–556 μm (ẋ = 446 ± 39 µm; CV = 9; N = 52 on 3 specimens) long by 331–490 μm (ẋ = 399 ± 36 µm; CV = 9; N = 52 on 3 specimens) wide (Fig. 14.3). Frontal shield pustulose, pierced by up to eight elliptical areolar pores at the lateral and distolateral margins. Orifice centrally located on the frontal shield, circular to longitudinally elliptical, 179–248 μm (ẋ = 208 ± 15 µm; CV = 7; N = 52 on 3 specimens) long by 161–249 μm (ẋ = 199 ± 21 µm; CV = 11; N = 52 on 3 specimens) wide, slightly larger in fertile autozooids, lateral condyles at midline or slightly proximal to the midline. Operculum semielliptical. Spine bases not observed. Ovicells hyperstomial, globular, 219–299 μm (ẋ = 259 ± 57 µm; CV = 22; N = 2 on 1 specimen) long by 301–365 μm (ẋ = 339 ± 22 µm; CV = 6; N = 6 on 2 specimens) wide, closed by the operculum; endooecium membranous; ectooecia granular, evenly pierced by circular pseudopores (Fig. 14.4).

Avicularia monomorphic, adventitious, single, oral, distal or distolateral to the orifice in each infertile autozooid while lateral to the brood chamber in fertile autozooids, directed laterally or distolaterally in infertile, and distally in fertile autozooids, asymmetrical, oriented sinistrally, acuminate, 203–331 μm (ẋ = 262 ± 34 µm; CV = 13; N = 52 on 3 specimens) long by 93–213 μm (ẋ = 140 ± 29 µm; CV = 21; N = 52 on 3 specimens) wide (Fig. 14.3–4). Crossbar complete, located at about one-third the avicularian length and separating the rounded proximal portion from the rostrum. Rostrum spatulate, well-rounded, slightly curved towards the orifice or ovicell, directed laterally or distolaterally in infertile autozooids while directed distally in fertile autozooids. Mandible slightly longer than avicularium, acute.

Kenozooids not observed.

Remarks. Anoteropora latirostris is a widespread species known from several tropical regions of the Indian Ocean. However, Cook & Chimonides (1994b) noted significant morphological differences between specimens from South Africa and those from the Arabian realm, suggesting that multiple species may be involved. The type material of Silén (1947) was collected during the Vega Expedition (1878–1880) from the Gulf of Aden. This material was recently re-examined and reimaged by Di Martino (2023), who designated a lectotype from a site precisely located between ME5 stations 236 KD and 283 KU at 12° 26′N, 44°16′E. Although the Vega samples are poorly preserved, they are completely identical to our material from the R.V. Meteor expedition.

The ultrastructure of Anoteropora latirostris was studied by Jacob et al. (2019), revealing that its skeleton is bimineralic, with asymmetric mineralization of the lateral walls. The colonies of Anoteropora latirostris are anchored by rhizoids that extend from the basal surface, though these structures were not observed in our material. Notably, in infertile autozooids, the avicularia are consistently oriented to one side (Fig. 14.3), whereas in fertile autozooids, they are positioned laterally to the brood chamber (Fig. 14.4). This latter characteristic is the primary feature distinguishing Anoteropora latirostris from Anoteropora magnicapitata Canu & Bassler, 1927, as well as from other comparable species.