Nevianipora undetermined

Nevianipora sp. (Fig. 21.1–6) Material examined. SMF 40798 (St. 283 KU; Fig. 21.1), SMF 40798 (St. 283 KU), SMF 40811 (St. 283 KU; Fig. 21.2, 21.4–6), SMF 40812 (2 specimens; St. 283 KU; A = Fig. 21.2, B = Fig. 21.3). Description. Colonies rigidly erect, multiserial, dichotomously branching at acute angles, forming cylindrical branches (Fig. 21.1–3). Zooids arranged in irregular whorls around branches. Ancestrula and early astogeny not observed. Autozooids fixed-walled, tubular, 505–986 μm (ẋ = 723 ± 144 µm; CV = 20; N = 30 on 2 specimens) long by 124–271 μm (ẋ = 197 ± 34 µm; CV = 17; N = 30 on 2 specimens) wide, with densely pseudoporous and flat to slightly convex frontal walls crossed by weak growth bands (Fig. 21.4–5). Pseudopores circular, longitudinally elliptical or polygonal in outline, 114–266 μm (ẋ = 180 ± 47 µm; CV = 26; N = 30 on 2 specimens) long by 118–224 μm (ẋ = 156 ± 31 µm; CV = 20; N = 30 on 2 specimens) wide. Zooidal boundaries often well defined by shallow grooves, but sometimes indistinct. Basal and lateral walls infrequently pierced by circular pores (Fig. 21.6). Autozooidal apertures subcircular, 8–19 μm (ẋ = 13 ± 3 µm; CV = 24; N = 30 on 2 specimens) long by 5–14 μm (ẋ = 8 ± 2 µm; CV = 25; N = 30 on 2 specimens) wide. Peristomes long and salient, often broken. Terminal diaphragms rare, sunken and pierced by pseudopores (Fig. 21.4). Gonozooids and other polymorphs not observed. Remarks. Several dozen colonies of Nevianipora sp. were recovered from station 283 KU southwest of Aden. The material closely resembles Nevianipora pulcherrima (Kirkpatrick, 1890), originally described from the Spratly Islands in the South China Sea, and subsequently reported from other regions of the mid Indo-Pacific (e.g., Scholz 1991). Records of Nevianipora pulcherrima from East Africa have been provided by Brood (1976) and d’Hondt (2018), while Brood (1980) also listed the species from the Red Sea. However, as no gonozooids were observed in the present material, we refrain from assigning the specimens to the species level and maintain them in open nomenclature as Nevianipora sp. This is, to our knowledge, the first documented occurrence of a cyclostome bryozoan from the Gulf of Aden.