Characodoma babelmandebi Martha & Scholz, 2025, sp. nov.

Characodoma babelmandebi sp. nov. urn:lsid:zoobank.org:act: E88CD87C-40F5-487B-8C67-2D88810169FC (Fig. 15.1–4) Material examined. Holotype: SMF 1808 (large specimen; St. 236 KD; Fig. 15.1–4). Additional material: SMF 1808 (small specimen; St. 236 KD). Etymology. Named for the type locality of the species, the Bab-el-Mandeb Strait. Description. Colony presumably encrusting, multiserial, unilamellar (Fig. 15.1). Zooids arranged quincuncially, separated by broad and distinct furrows. Pore chambers not observed. Ancestrula and early astogeny not observed. Autozooids irregularly polygonal to subhexagonal, 222–409 μm (ẋ = 320 ± 48 µm; CV = 15; N = 15 on 1 specimen) long by 226–360 μm (ẋ = 298 ± 42 µm; CV = 14; N = 15 on 1 specimen) wide (Fig. 15.2). Frontal shield convex, variably tuberculate, irregularly pierced by c. 4–10 circular to elliptical areolar pores at the margins and c. 1–4 circular pores proximal to the avicularian rostrum (Fig. 15.3). Orifice terminal, keyhole-shaped; anter elliptical, 86–111 μm (ẋ = 100 ± 7 µm; CV = 7; N = 15 on 1 specimen) long by 73–91 μm (ẋ = 79 ± 5 µm; CV = 6; N = 15 on 1 specimen) wide, separated by proximomedially directed condyles from the poster; poster semielliptical, well-rounded proximally, 26–39 μm (ẋ = 35 ± 4 µm; CV = 11; N = 15 on 1 specimen) long by 28–40 μm (ẋ = 35 ± 4 µm; CV = 11; N = 15 on 1 specimen) wide. Spine bases not observed. Ovicells hyperstomial, helmet-shaped, 118–147 μm (ẋ = 131 ± 8 µm; CV = 6; N = 15 on 1 specimen) long by 132–183 μm (ẋ = 163 ± 14 µm; CV = 9; N = 15 on 1 specimen) wide, acleithral; ectooecia finely tuberculate, pierced centrally by an oblong to slit-like pore (Fig. 15.4). Avicularia dimorphic in size, adventitious, usually single, rarely paired. Large avicularia lateral to the orifice, bilaterally symmetrical, oblong, 228–273 μm (ẋ = 250 ± 13 µm; CV = 5; N = 15 on 1 specimen) long by 109–138 μm (ẋ = 124 ± 10 µm; CV = 8; N = 15 on 1 specimen) wide (Fig. 15.3). Avicularian aperture inversely teardrop-shaped, 77–131 μm (ẋ = 100 ± 12 µm; CV = 12; N = 15 on 1 specimen) long by 44–64 μm (ẋ = 52 ± 6 µm; CV = 11; N = 15 on 1 specimen) wide; crossbar complete but usually broken in observed specimens, at about one-third to one-fourth the avicularian aperture length. Rostrum spatulate, proximally directed. Small avicularia lateral to the orifice, bilaterally symmetrical, kite-shaped, 90–134 μm (ẋ = 110 ± 13 µm; CV = 12; N = 15 on 1 specimen) long by 89–121 μm (ẋ = 105 ± 11 µm; CV = 10; N = 15 on 1 specimen) wide (Fig. 15.3). Avicularian aperture inversely teardrop-shaped, 44–67 μm (ẋ = 59 ± 8 µm; CV = 13; N = 15 on 1 specimen) long by 31–57 μm (ẋ = 46 ± 9 µm; CV = 19; N = 15 on 1 specimen) wide; crossbar complete, separating rounded proximal portion from triangular rostrum. Rostrum acute, markedly elevated, proximolaterally directed. Kenozooids not observed. Remarks. Characodoma babelmandebi sp. nov. is described based on two colonies collected from shallow waters off the coast of Djibouti. Although the substrate is not preserved, the species is presumed to be encrusting. Characodoma babelmandebi sp. nov. differs from Characodoma protrusum (Thornely, 1905), a species found in deeper waters of the Gulf of Aden, by having fewer (areolar) pores piercing the frontal shield, dimorphic avicularia, and a distinctive ovicell morphology (Fig. 15.4). Notably, the ovicell in Characodoma babelmandebi sp. nov. is unique among known Characodoma species in possessing an ectooecium pierced by a single, large central foramen (Fig. 15.4). In contrast, other congeners either have an imperforate ectooecium or one perforated by numerous small pores (e.g., Characodoma protrusum). The new species most closely resembles Characodoma mamillatum (Seguenza, 1880), originally described from the Calabrian (Pleistocene) of Gallina, a suburb of Reggio Calabria, Italy. Rosso (1999) revised this species and synonymised the recent Lepralia bifurcata Waters, 1918 with Characodoma mamillatum, which is now known from both fossil and extant material in the central Mediterranean, particularly around southern Italy. In Characodoma mamillatum, small adventitious avicularia are typically paired lateral to the orifice, with larger avicularia oriented distally, while the smaller ones are directed laterally to slightly distolaterally. In contrast, avicularia in Characodoma babelmandebi sp. nov. are oriented proximally and proximolaterally, respectively (Fig. 15.2). Furthermore, the poster in Characodoma mamillatum is significantly shorter and broader than in Characodoma babelmandebi sp. nov., and areolar pores piercing the frontal shield are lacking. Rosso (1999, fig. 10) documented successive stages of ovicell development in Characodoma mamillatum, showing that calcification begins at the lateral wings and proceeds centrally. Incompletely calcified ovicells in this species may resemble the seemingly “cracked” ovicells observed in Characodoma babelmandebi sp. nov. However, in the latter, a central oblong or slit-like fenestra remains open in the ectooecium even in fully developed ovicells (Fig. 15.4), whereas in Characodoma mamillatum, the ectooecium becomes fully calcified upon completion.