Porina australiensis (Haswell, 1880)

(Fig. 18.1–5)

Myriozoum australiense Haswell, 1880: 43, pl. III, figs 9–11.

Haswellia australiensis: Busk 1884: 172, pl. XXIV, fig. 9A–H; Levinsen 1909: 297, pl. XVI, fig. 2a–b; Canu 1913: 444; Waters 1913: 511; Canu & Bassler 1920: figs 148C, 150A–K; Marcus 1921: 18; Robertson 1921: 59; Marcus 1922: 434; Canu & Bassler 1929: 281, text-fig. 44C, pl. 30, figs 6–9; Lu 1991: pl. II, figs 7, 8.

Porina australiensis: Di Martino & Taylor 2018: 39, figs 116–119.

Spiroporina vertebralis: partim Harmer 1957: 847, pl. LVI, figs 1–6; non Spiroporina vertebralis Stoliczka, 1865.

Margaretta watersii: Symphonia & Nathan 2022: fig. 5.3–4; non Tubucellaria watersi Canu & Bassler, 1930.

Material examined. SMF 40787 (St. 283 KU; Fig. 18.4), SMF 40796 (St. 283 KU; Fig. 18.2), SMF 40810 (St. 283 KU; Fig. 18.1, 18.3, 18.5), SMF 61357 (2 specimens; St. 236 KD).

Description. Colonies rigidly erect, cylindrical, multiserial, dichotomously branching (Fig. 18.1–3).Autozooidal outlines not evident frontally (Fig. 18.2). Zooidal peristomes form whorls of six, arranged in alternating, longitudinal series along cylindrical branches. Ancestrula and early astogeny not observed.

Frontal shield flat, evenly pierced by longitudinally elliptical or circular pseudopores arranged in longitudinal rows, weakly raised proximal to the peristome and strongly raised on all other sides of peristome (Fig. 18.4). Spiramina non-projecting, single; outer opening located at the base of peristome, circular to longitudinally elliptical, 41–75 μm (ẋ = 57 ± 8 µm; CV = 14; N = 38 on 3 specimens) long by 35–70 μm (ẋ = 48 ± 7 µm; CV = 15; N = 38 on 3 specimens) wide. Primary orifice obscured by peristome; condyles not observed. Peristome salient, evenly pierced by longitudinally elliptical or circular pseudopores arranged in longitudinal rows (Fig. 18.5). Secondary orifice circular, 108–178 μm (ẋ = 141 ± 19 µm; CV = 13; N = 42 on 3 specimens) in diameter. Spine bases and ovicells not observed.

Avicularia monomorphic, adventitious, located in elliptical pores at equal proximolateral distance between two peristomes, bilaterally symmetrical, ovate, 48–79 μm (ẋ = 61 ± 8 µm; CV = 13; N = 36 on 3 specimens) long by 25–59 μm (ẋ = 39 ± 8 µm; CV = 21; N = 36 on 3 specimens) wide; crossbar complete, located at about one-third the avicularian length (Fig. 18.4). Rostrum spatulate, elevated, proximally directed.

Kenozooids not observed.

Remarks. Porina australiensis is widely reported from Australian waters and the Coral Triangle. Waters (1913) was the first to document this species from the western Indian Ocean, but without providing illustrations of his specimens from the coast of Wasini Island, Kenya. Non-type material of Porina australiensis from Wednesday Island, Queensland, Australia was recently imaged by Di Martino & Taylor (2018, figs 120–123). The colony from Torres Strait closely resembles our specimens from the Gulf of Aden and Bab-el-Mandeb Strait, though the autozooids appear shorter. Additionally, we did not observe peristomial avicularia in our specimens; however, this may be due to preservational issues, as the peristomes are all incompletely preserved. Single (Fig. 18.5) or paired (Fig. 18.4) hollows at the proximal margin of the peristome may represent remnants of avicularia.

Canu & Bassler (1917) subsequently selected Porina australiensis as the type species of the genus Haswellina Livingstone, 1928, a replacement name for the pre-occupied Haswellia Busk, 1884. The validity of Haswellina was debated (e.g., Uttley 1956; Brown 1958), particularly regarding whether it was a junior synonym of either Spiroporina Stoliczka, 1865, or Porina. Ultimately, Gordon & d’Hondt (1997) considered both Haswellina and Spiroporina to be subjective junior synonyms of Porina, rendering Porina australiensis type species of an invalid genus.