Taxonomy and diversity of coelobite bryozoans from drift coral cobbles on Co To Island, northern Vietnam Author Dick, Matthew H. Author Ngai, Nguyen Danh Author Doan, Hung Dinh text Zootaxa 2020 2020-03-03 4747 2 201 252 journal article 10.11646/zootaxa.4747.2.1 55ab330e-0468-42ed-aeb0-7850751cf989 1175-5326 3694740 6AA8F5DC-8D70-42B0-B016-6F9C4211C471 Celleporaria triangula Seo, 1994 ( Fig. 7 A–D) Celleporaria triangula Seo, 1994 , p. 190 , pls 1, 2. Celleporaria triangula : Dick & Grischenko 2017 , p. 187 , fig. 14f–h. Material examined. VNMN-0227 (CT-33), on SEM stub. VNMN-0228, three badly worn specimens. Measurements. AzL , 0.40–0.54 (0.465 ± 0.042); AzW , 0.28–0.41 (0.315 ±0.041); OrL , 0.10–0.13 (0.119 ±0.008); OrW , 0.13–0.16 (0.147 ± 0.010) (n = 15, 1). OvL , 0.17–0.21 (0.185 ±0.023); OvW , 0.21–0.27 (0.226 ± 0.020) (n = 4, 1). Description. Colony low, encrusting, multilaminar. Zooids distinct, delineated by groove; variably oriented with indistinct boundaries in layers other than basal layer. Frontal wall convex, imperforate, evenly coarsely pustulose, with three to seven small, circular areolae along each lateral margin. Orifice broader than long, D-shaped; proximal margin straight or slightly concave, irregular, typically with large and small sinus side by side, each bounded laterally by sharp projection, separated by sharp or truncate median denticle. Main oral sinus varies greatly in depth; sometimes scarcely evident. With age, primary orifice slightly sunken, surrounded by peristomial collar. Three or four short, ephemeral oral spines or spine bases evident in some marginal zooids. Small avicularium proximal to orifice, offset to one side or other of midline, on small chamber on peristomial collar, rostrum pointing frontolaterally or frontodistolaterally; mandible rounded, crossbar complete. Interzooidal avicularium large, with semi-elliptical mandible. Ooecium cucullate (hood shaped), with broad, semicircular opening. Remarks. Only a single non-worn specimen was obtained, which bore only one interzooidal avicularium. In zooid size, zooid morphology, shape of the interzooidal avicularium, and the shapes of (and variation in) the oral sinuses, this specimen greatly resembles specimens from Okinawa , Japan , reported as Celleporaria triangula by Dick & Grischenko (2017) . However, zooids at Co To differ from both the Okinawa population and the Korean population originally described ( Seo 1994 ) in having three or four rather than one or two short, ephemeral oral spines or spine bases evident in marginal zooids. The Korean population differs from those at both Co To and Okinawa in having deeper oral sinuses and wider, more pronounced median and flanking projections, and in having some of the vicarious avicularia narrower, almost lanceolate. Finally, in both the Co To and Okinawa populations, the fully formed cucullate ooecia appear to have the opening facing frontally, rather than oriented perpendicular to the colony surface and facing proximally. While these differences might indicate that the Okinawa and Co To populations are not conspecific with the Korean population, we retain the name C. triangula for all three, until more material can be examined from Korea southward. The variation in the proximal orificial margin within colonies at Okinawa and Co To mirrors to a great extent the variation that Harmer (1957 , p. 674, text-fig. 56) illustrated for nominal C. aperta ( Hincks, 1882 ) . This latter species, however, both in the original description ( Hincks 1882 ) and subsequently ( Winston & Heimberg 1986 ; Ryland & Hayward 1992), has a single median oral sinus, very different from the condition in C. triangula . A significant proportion of the material Harmer (1957) attributed to C. aperta may actually be C. triangula or belong to a species complex that includes C. triangula . Distribution . Previously reported only from southern Korea and Okinawa , Japan .