Setosella spiralis Silen 1942

• Main Authors: Rosso, A., Martino, E. Di, Gerovasileiou, V.
• Format: Other/Unknown Material
• Language: unknown
• Published: 2020
• Subjects: Biodiversity; Taxonomy; Animalia; Bryozoa; Gymnolaemata; Cheilostomatida; Setosellidae; Setosella; Setosella spiralis; Josephine; North Atlantic
• Online Access: https://zenodo.org/record/5586289; https://doi.org/10.5281/zenodo.5586289

Setosella spiralis Silén, 1942 (Figs 15–17; Tables 1, 2, 5) Setosella spiralis Silén, 1942: p. 4, fig. 3; pl. 2, fig. 7. Examined material. Holotype SMNH-Type-1893, North Atlantic Ocean, Josephine Bank, 36°45,5’N, 14°12,2’W, 340–430 fathoms (c. 500–650 m), Josephine Expedition 1869, a dead colony on the external surface of a bivalve. Paratypes, same collection number and details as the holotype: (1) five dead colonies, two on internal surfaces of bivalve shells, one on an unidentified bioclast, and two on a 4x 2.5x 2.5 cm biogenic concretion; (2) a live colony on a bioclast. Description. Colony small, including c. 20 zooids, exceptionally 37 in the largest available colony, entirely adhering to the substratum, consisting of spirally arranged zooids typically in a single right-coiled row and tightly adherent whorls giving a very solid appearance (Figs 15a, 16a). Each autozooid budding a disto-lateral daughter zooid from an elliptical septulum (30–45 µm long) located at about mid-length on the right side (Figs 15a, b, 16a, b, 17). A smaller, comparably more distally located subcircular pore (15–20 µm wide) present on its left side, seemingly inactive at the periphery of the colony, but functional to connect zooids in two subsequent whorls. New budded zooids variable in position in relation to the parental zooid, from disto-lateral at an angle of c. 45° with the longitudinal axis of the parental zooid, to mid-lateral or even proximo-lateral and subparallel (or sometimes orthogonal) with the longitudinal axis of the parental zooid. In one of the paratypes, the second periancestrular zooid contemporaneously buds three zooids (one distally and two disto-laterally) developing a ‘triple’ spiral (Fig. 17). Autozooids thick in lateral view (Figs 15e, 16d), irregularly elongate and asymmetrical in frontal view, with a cuneiform proximal end and a straight oblique termination on the left side contributing to the continuous, regularly curved colony edge. Lateral gymnocyst contributing to zooidal asymmetry, extensively ...