Labioporella crenulata

Labioporella crenulata (Levinsen, 1909) (Fig. 3.1–4) Labiopora crenulata Levinsen, 1909: 174, pl. VI, fig. 4a. Labioporella crenulata: Harmer 1926: 282, pl. XXI, figs 1–3; Cook et al. 2018: fig. 3.30; Canu & Bassler 1929: 148, pl. 16, figs 2, 3;? Kataoka, 1961: 237. Material examined. SMF 40801 (4 specimens; St. 283 KU; Fig. 3.1–4). Description. Colonies encrusting, multiserial, unilamellar (Fig. 3.1–2). Zooids arranged quincuncially, separated by broad and distinct furrows. Pore chambers, ancestrula and early astogeny not observed. Autozooids elongate, with inwardly curved proximal side and outwardly curved distal side, 569–820 μm (ẋ = 653 ± 76 µm; CV = 12; N = 15 on 1 specimen) long by 250–331 μm (ẋ = 298 ± 21 µm; CV = 7; N = 15 on 1 specimen) wide (Fig. 3.3–4). Gymnocyst not visible. Cryptocyst sunken centrally, raised around the rims, pustulose, pierced by circular pores centrally and proximally, pores becoming smaller proximally, imperforate distally, with two circular depressions flanking polypide tube, occasionally partly or fully covered by imperforate lamina (Fig. 3.2, 3.4). Polypide tube convex frontally, with transversely elliptical aperture. Opesia terminal, semielliptical, with pinnately lobed lateral margins, bearing short and broad opesiular indentations at proximolateral corners, 170–219 μm (ẋ = 190 ± 13 µm; CV = 7; N = 15 on 1 specimen) long by 173–210 μm (ẋ = 192 ± 10 µm; CV = 5; N = 15 on 1 specimen) wide. Spine bases and ovicells not observed. Avicularia not observed. Kenozooids rare, shorter than autozooids. Kenozooidal cryptocyst smooth, with subterminal, longitudinally elliptical aperture (Fig. 3.2). Remarks. Dumont (1981) reported Labioporella crenulata from the Sudanese Red Sea but did not provide any images. Our specimens from the Gulf of Aden lack avicularia, despite the fact that the imaged colony is large with over 100 autozooids. The low occurrence or complete absence of avicularia in Labioporella colonies is not uncommon and complicates taxonomic identification. Levinsen (1909) noted the presence of avicularia in the type material he examined, but the autozooid morphology in the specimens we studied is identical to that of Labioporella crenulata from the central Indo-Pacific (as per Cook et al. 2018). Since we do not consider the absence of avicularia sufficient to distinguish a separate species, we assign the studied material to Labioporella crenulata. The only reported possible fossil occurrence of Labioporella crenulata comes from a limestone of Pleistocene age collected near Kamikatetsu on Kikaijima, Kagoshima Prefecture, Japan (Kataoka 1961). However, because the species was not imaged in that study, the identification remains uncertain. The family Labioporellidae Harmer, 1926, was long considered unjustified, and Labioporella was instead placed in Steginoporellidae Hincks, 1884, by Canu & Bassler (1929), Bassler (1953), and most subsequent authors. However, Winston & Jackson (2021) used Labioporellidae without further comment. Recent molecular data (Grant et al. 2023) now suggests that Labioporellidae may indeed warrant resurrection.