Plesiocleidochasma dorothyjohnella, Martha & Scholz, 2025

Plesiocleidochasma dorothyjohnella sp. nov.

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( Fig. 11.1–4 View FIGURE 11 )

Material examined. Holotype: SMF 40800 About SMF (St. 283 KU; Fig. 11.1–4 View FIGURE 11 ).

Etymology. Named in honour of Dorothy Fisher Soule, née Dorothy Louise Fisher (1923–2005) and John Dutcher Soule (1920–2001) in recognition of their contributions to bryozoan research.

Description. Colony encrusting, multiserial, unilamellar ( Fig. 11.1 View FIGURE 11 ). Zooids arranged quincuncially, separated by broad and distinct furrows. Septula inside vertical walls monoporous, circular. Ancestrula tatiform, obscured by surrounding autozooids ( Fig. 11.2 View FIGURE 11 ).

Autozooids hexagonal, 308–404 μm (ẋ = 345 ± 23 µm; CV = 7; N = 15 on 1 specimen) long by 276–351 μm (ẋ = 310 ± 25 µm; CV = 8; N = 15 on 1 specimen) wide. Frontal shield slightly convex, ornamented with regularly arranged pustules on smooth calcification, pierced by 4–10 circular areolar pores at the margins. Orifice subterminal, keyhole-shaped; anter circular to slightly elliptical, 60–77 μm (ẋ = 70 ± 5 µm; CV = 7; N = 12 on 1 specimen) long by 67–88 μm (ẋ = 80 ± 6 µm; CV = 7; N = 12 on 1 specimen) wide, separated by proximomedially directed condyles from the narrower, semielliptical poster, 23–34 μm (ẋ = 28 ± 3 µm; CV = 12; N = 12 on 1 specimen) long by 21–34 μm (ẋ = 29 ± 3 µm; CV = 12; N = 12 on 1 specimen) wide ( Fig. 11.3 View FIGURE 11 ). Intramural reparative budding inside autozooidal orifices common, indicated by two orificial rims ( Fig. 11.4 View FIGURE 11 ). Spine bases oral, numbering two, (disto)lateral to the orifice, occasionally third spine bases distal to the orifice. Ovicells not observed .

Avicularia dimorphic, adventitious, single, proximolateral to the orifice, on a few autozooids only, bilaterally symmetrical, ovate, occasionally enlarged and elliptical. Small avicularia acuminate, 68–71 μm (ẋ = 70 ± 2 µm; CV = 3; N = 2 on 1 specimen) long by 53–55 μm (ẋ = 54 ± 1 µm; CV = 3; N = 2 on 1 specimen) wide ( Fig. 11.2 View FIGURE 11 ). Large avicularia rectangular with rounded corners, 118–149 μm (ẋ = 136 ± 16 µm; CV = 12; N = 3 on 1 specimen) long by 68–70 μm (ẋ = 69 ± 1 µm; CV = 1; N = 3 on 1 specimen) wide ( Fig. 11.4 View FIGURE 11 ). Avicularian aperture ovate, occupying most of the frontal surface. Crossbar complete, located at about one-third the avicularian aperture length. Rostrum acuminate, occasionally prolonged and spatulate, directed proximally or proximolaterally .

Kenozooids not observed.

Remarks. Plesiocleidochasma is a widespread genus found in tropical waters, comprising nearly two dozen closely-related species. Two species later assigned to Plesiocleidochasma were previously mentioned from the Red Sea by Dumont (1981) without accompanying images; Plesiocleidochasma laterale ( Harmer, 1957) and Plesiocleidochasma porcellanum ( Busk, 1860) . Plesiocleidochasma laterale differs from Plesiocleidochasma dorothyJohnella sp. nov. by its single or paired avicularia with trifoliate apertures, a very short and broad crescentshaped poster, and fewer areolar pores. Plesiocleidochasma porcellanum is distinguished by its short, broad poster, 3–4 oral spines, and fewer areolar pores. Additionally, both species have trifoliate avicularian opesiae, whereas Plesiocleidochasma dorothyJohnella sp. nov. has ovate avicularian opesiae.

Another comparable species, Plesiocleidochasma porcellaniforme ( Soule, Soule & Chaney, 1991) from the southwestern Pacific Ocean, usually has paired avicularia proximolateral to the orifice with an acute rostral tip, and lacks oral spine bases. In the type species, Plesiocleidochasma normani ( Livingstone, 1926) , from the Surprise Shoal, Coral Sea off Queensland, Australia, early astogeny autozooids may possess up to three oral spine bases. However, its avicularia are characterised by a long, acuminate rostrum, while the poster is short and nearly as broad as the anter (see Soule et al. 1991).

Plesiocleidochasma dorothyJohnella sp. nov. is notable for exhibiting avicularian dimorphism. Some avicularia feature a short, acuminate rostrum surrounding the avicularian aperture, while others have a spatulate rostrum. Avicularian size dimorphism has been previously documented in Plesiocleidochasma species, such as Plesiocleidochasma laterale . In Plesiocleidochasma dorothyJohnella sp. nov., avicularia with a spatulate rostrum are twice as long as those with an acute rostrum, as they have cryptocystal calcification extending from the avicularian aperture to the rostral tip ( Fig. 11.4 View FIGURE 11 ). The ovicell of this new species from the Gulf of Aden remains unknown.