Stomhypselosaria simplex, Hayward & Winston, 2011

Hayward, Peter J. & Winston, Judith E., 2011, Bryozoa collected by the United States Antarctic Research Program: new taxa and new records, Journal of Natural History 45 (37 - 38), pp. 2259-2338 : 2279-2280

Stomhypselosaria simplex sp. nov.

( Figure 10A, B )

Material

Holotype. NMNH 1154055 : Eltanin cruise 12, station 991, 60 ◦ 57’ to 60 ◦ 54’ S, 56 ◦ 52’ to 56 ◦ 58’ W, 2672–3020 m, 13 March 1964, part of a colony, 12 mm high, with three dichotomies.

Paratypes. NMNH 1154056 : same data as holotype; more than 20 fragments, to 17 mm long, representing parts of at least three colonies, one basal portion with attached rhizoids .

Description

Colony erect, branching, rigid, unjointed, attached by chitinous rhizoids. Branches cylindrical, consisting of four alternating whorls of autozooids; dichotomies irregular, at variable intervals, internodes straight. Autozooids regularly hexagonal, bounded by distinct, raised ridges; frontal membrane conspicuous, with thick, brown border to each autozooid. Opesia in distal half of autozooid, separated from distal border by a distance equivalent to its length, about as wide as long, its rim slightly raised above frontal surface of autozooid, the proximal edge straight but reflected frontally and appearing slightly convex; a pair of very small, obscure denticles within distal rim, revealed by SEM. Cryptocyst finely and uniformly granular, dipping away from margins, more or less flat but slightly convex medially and with an indistinct pair of cryptocystal ridges developing in later ontogeny, extending to proximal third of autozooid and converging medially. Each dichotomy with a polygonal kenozooid, as large as an autozooid, with a complete, oval, cryptocystal ridge and a small, round central foramen. No ovicells present. No avicularia apparent in material available.

Measurements

For all measurements, n = 20, mean ± SD: autozooid length 1.05 ± 0.07 mm; autozooid width 0.66 ± 0.07 mm; opesia length 0.16 ± 0.01 mm; opesia width 0.20 ± 0.01 mm.

Etymology

Latin, simplex : simplicity, with reference to autozooidal morphology. Remarks

Generic assignment of this species must be considered provisional. It is not easily referable to any southern hemisphere cellariid genus, but its rigid, unjointed colony form, and the axial kenozooid, suggest that it is closest to Stomhypselosaria . Its apparent morphological simplicity suggests that the sample did not comprise a complete ontogenetic series, and certainly further material, including fertile zooids, is required before its systematic identity can be confirmed.

Figures

Figure 10. (A,B) Stomhypselosaria simplex sp. nov., Paratype. (A) Part of branch, with dichotomy; (B) detail of opesia. (C, D) Membranicellaria dubia, Eltanin (27) stn. 1870. (C) Autozooids in late ontogeny, with occluded opesiae; (D) auotozooids in early ontogeny (top), and others with developing occlusions. Scale bars: 1.0 mm (A), 0.1 mm (B, C, D).