Microporella setiformis O'Donoghue & O'Donoghue 1923

Microporella setiformis O’Donoghue & O’Donoghue, 1923 Fig. 9, Table 2 Microporella setiformis O’Donoghue & O’Donoghue, 1923: 174, pl. 3 fig. 21. Microporella setiformis – Osburn 1952: 385, pl. 44 fig. 8. — Soule et al. 1995: 150, pl. 53 figs a–d. — Dick et al. 2005: 3752, fig. 18c–d. Material examined USA • 1 living colony of 30 zooids, none ovicellate, on rock; California, Black Sand Beach; 40°24′50.5074″ N, 124°23′48.1056″ W; 9 Jun. 2020; I.A. Chowdhury and H. Lee leg.; SBMNH 704776a • 1 colony of 20 zooids, none ovicellate, on rock; California, Black Sand Beach; 40°24′50.5074″ N, 124°23′48.1056″ W; 9 Jun. 2020; I.A. Chowdhury and H. Lee leg.; SBMNH 704776b • 1 colony of 60 zooids, 18 ovicellate, on rock; California, Black Sand Beach; 40°24′50.5074″ N, 124°23′48.1056″ W; 9 Jun. 2020; I.A. Chowdhury and H. Lee leg.; SBMNH 704776c • 1 colony of 30 zooids, none ovicellate, on rock; California, Black Sand Beach; 40°24′50.5074″ N, 124°23′48.1056″ W; 9 Jun. 2020; I.A. Chowdhury and H. Lee leg.; SBMNH 704776d • 1 colony of 40 zooids, none ovicellate, on rock; California Black Sand Beach; 40°24′50.5074″ N, 124°23′48.1056″ W; 9 Jun. 2020; I.A. Chowdhury and H. Lee leg.; SBMNH 704776e • 1 colony of 60 zooids, 13 ovicellate, on rock; California, Black Sand Beach; 40°24′50.5074″ N, 124°23′48.1056″ W; 9 Jun. 2020; I.A. Chowdhury and H. Lee leg.; SBMNH 704776f. Description Colony encrusting, multiserial, unilaminar, forming subcircular patches, typically encrusting rocks of various sizes; pore chamber windows visible at the colony growing edge (Fig. 9E), circular to elliptical, three on distal margin and 4–5 on each distolateral vertical wall. Autozooids rounded hexagonal or irregularly polygonal, ZL = 377–540 µm (470±48 µm, N = 20), ZW = 272–439 µm (348±45 µm, N = 20), mean L/W = 1.30; boundaries marked by grooves between slightly raised vertical walls. Frontal shield flat to slightly convex, finely granular, with 52–89 circular pseudopores (D = 5–12 µm) and 10–12 circular to elliptical, marginal areolae per side, clearly distinguishable from pseudopores by their larger size (D = 10–22 µm) (Fig. 9A–B). Primary orifice transversely D-shaped, OL = 114–139 µm (124±8 µm, N = 10), OW = 120–148 µm (133±8 µm, N = 10), mean OL/OW = 0.93, mean ZL/OL = 3.80; outlined by rim of smooth gymnocyst; hinge-line straight, smooth, with two low, trapezoidal condyles at corners (Fig. 9C). Two oral spines observed in some zooids, later obscured by secondary calcification or ovicell (Fig. 9F). Ascopore unusually small, circular (18–25 µm in diameter), with smooth margin, covering plate lacking (Fig. 9C); at same level as adjacent frontal shield, 2–3 ascopore widths from orifice, outlined by rim of gymnocystal calcification independent from that encircling orifice. Avicularia small, single or paired, AvL = 40–51 µm (46±4 µm, N = 7), AvW = 21–30 µm (25±3 µm, N = 7), mean AvL/AvW = 1.85; located distally at same level as ascopore (Fig. 9C); crossbar complete (Fig. 9D); rostrum rounded-triangular, directed laterally or slightly distolaterally, rostrum tip only slightly raised. Mandible not observed. Ovicell prominent, round, wider than long (Fig. 9A, D); OvL = 194–281 µm (242±33 µm, N = 6), OvW = 305–363 µm (332±21 µm, N = 7), mean OvL/OvW = 0.73; continuous with frontal shield of next distal zooid, obscuring distal margin of maternal orifice; calcification finely granular like that of frontal shield but with marked ribs; perforated by small pseudopores, 5–14 µm in maximum dimension. Aberrant kenozooids smaller than autozooids or nearly as large, lacking opening such as orifice and ascopore but equipped with avicularium (Fig. 9B, see asterisks). Ancestrula not observed. Remarks Our material fits the description of Microporella setiformis, a species originally described from British Columbia, Canada (O’Donoghue & O’Donoghue 1923). Distribution and ecology Microporella setiformis has been recorded from intertidal waters to over 100 m depth. The species ranges from Ketchikan, Alaska (Dick et al. 2005) southward Channel Islands in southern California (Soule et al. 1995).

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