Calloporina sigillata Canu & Bassler 1929

Calloporina sigillata Canu & Bassler, 1929

(Fig. 10 B–D)

Calloporina sigillata Canu & Bassler, 1929, p. 333, pl. 40, figs 9, 10.

Calloporina sigillata: Harmer 1957, p. 973, pl. 62, fig. 44; Ristedt and Hillmer 1985, p. 137, pl. 3, fig. 5; Tilbrook 2006, p. 216, pl. 47C–E.

Calloporina cf. sigillata: Scholz 1991, p. 316.

Material examined. VNMN-0241 (CT-16), VNMN-0242 (CT-30), on SEM stubs.

Measurements. AzL, 0.58–0.95 (0.723 ± 0.091); AzW, 0.45–0.64 (0.556 ± 0.055); OrL, 0.12–0.14 (0.124 ± 0.006); OrW, 0.12–0.14 (0.127 ± 0.006) (n = 15, 1). OvL, 0.29–0.36 (0.321 ± 0.021); OvW, 0.33–0.43 (0.405 ± 0.033) (n = 8, 2). Ancestrula: L × W, 0.485 × 0.294; opesia L × W, 0.226 × 0.187 (n = 1).

Description. Colony unilaminar, encrusting, sheet-like.

Zooids large, distinct, irregularly hexagonal, delineated by deep furrow. Frontal wall highly convex; nodulose; eight to 12 areolar pores close to margin and another, less numerous row of pseudopores inset from margin. Orifice subterminal, elevated; subcircular, proximal margin concave; small shelf-like condyles sometimes evident in proximolateral corners; with seven (n = 5) or eight (n = 6) oral spine bases in arc laterally and distally around orifice. Ascopore roughly in center of zooid, circular, surrounded by rim.

Large adventitious avicularia proximolateral to orifice, rostrum long, tapering, extending to either side of orifice; usually paired, but sometimes single or lacking; when paired, usually (but not always) unequal in size; rostrum parallel-sided or tapering, distal end acute.

Ooecium prominent, broader than long, with transversely oriented, C-shaped ridge covered by non-calcified ectooecium (?), exposing minutely perforate endooecium (?) after bleaching, open end of ‘C’ facing proximally; frontal calcification from next-distal zooid forming broad, smooth peripheral band around ooecium laterally and distally; two spine bases visible on each side of orifice proximal to ooecium.

Ancestrula tatiform, with numerous spines; one avicularium observed but spine count not possible; initially budding distal (and one distolateral?) zooid, followed by spiral budding pattern on one side.

Remarks. This species is readily distinguished from congeners by its large zooids; more than one series of marginal pores; seven or eight oral spines; the smooth proximal orifical margin; large, acute, usually paired frontal avicularia proximolateral and lateral to the orifice, directed distally or distolaterally, unequal in size when paired; the rimmed, circular ascopore in the center of the zooidal area, distant from the orifice; and the ooecium with a Cshaped, minutely perforate transverse ridge.

Distribution. Originally described from the Philippines (Canu & Bassler 1929), this species has subsequently been reported from Tizard Bank in the Spratly Islands; Taiwan Strait; Sumbawa, Indonesia; the Great Barrier Reef, western Australia; and the Solomon Islands (Tilbrook 2006).