Parasmittina parsevalioidea Liu, 2001

Dick, Matthew H., Ngai, Nguyen Danh & Doan, Hung Dinh, 2020, Taxonomy and diversity of coelobite bryozoans from drift coral cobbles on Co To Island, northern Vietnam, Zootaxa 4747 (2), pp. 201-252 : 219

Parasmittina parsevalioidea Liu, 2001

( Figs 8 , 20D )

Parasmittina parsevalioidea Liu, 2001 in Liu et al. 2001, p. 625 , pl. 56, figs 1–4.

Material examined. VNMN-0229 (CT-12), VNMN-0230 (CT-22), VNMN-0231 (CT-23), VNMN-0232 (CT-27), VNMN-0233 (CT-39), VNMN-0234 (CT-43), all on SEM stubs; VNMN-0235, 13 colonies and fragments.

Measurements. AzL, 0.41–0.65 (0.504 ± 0.060); AzW, 0.24–0.39 (0.311 ± 0.044); OrL, 0.082 –0.112 (0.096 ± 0.008); OrW, 0.083 –0.102 (0.093 ± 0.006); OvL, 0.18–0.21 (0.193 ± 0.009); OvW, 0.19–0.24 (0.215 ±0.013) (n = 15, 1).

Description. Colony encrusting, unilaminar, sheet-like.

Zooids variable in shape (sub-rectangular, oval, spindle-shaped, irregularly polygonal), distinct, delineated by raised line of calcification between adjacent rows of marginal pores (circular, five to 10 along each lateral margin). Frontal wall slightly convex, imperforate, entirely coarsely pustulose. Primary orifice semicircular distally, widest at condyles; distal margin smooth; low, wide, non-alate median lyrula; strong, curved, tusk-like, acute, proximomedially directed condyles originating just proximal to widest part of orifice, finely denticulate along curved edge. Sharp peristomial lip surrounding orifice proximally and laterally, often forming raised lateral flanges. Oral spine bases, when evident, predominantly two, but occasional zooids with one, three, or four.

Adventitious avicularia polymorphic, including the following types. 1) Small oral avicularium with short-triangular mandible, usually lateral to and directed toward orifice, tip of rostrum reaching top of peristomial flange, crossbar complete unless damaged; often degenerate, rostrum replaced by irregular opening; single, or often lacking. 2) Oval, shoe-shaped, or rounded-quadrate frontal avicularia, somewhat larger than oral avicularia, occurring proximally or laterally on frontal wall; one or occasionally two per zooid when present, lacking in many zooids; mandible short-spatulate, wider distally than proximally, pointing in any direction; crossbar usually incomplete but sometimes complete. 3) Large, spatulate avicularium originating lateral or distolateral to orifice, extending to lateral corner of zooid, directed proximolaterally; sides of rostrum parallel for about half rostral length, then expanding to spatulate end, about twice width of proximal portion; rim of rostrum smooth; large avicularia uncommon in Co To specimens and lacking in some colony fragments.

Ooecium prominent, with about 25 pseudopores, imperforate in proximocentral area; periphery covered by narrow zone of pustulose frontal calcification from surrounding zooids; peristomial collar thickened, higher in ooeciate zooids, narrowing proximally as pseudosinus, extending part way onto ooecium on each side, occasionally forming complete collar across proximal part of ooecium. In reproductive parts of colony, large, secondary areolar openings surrounding peristome and ooecium, with calcified struts forming coarse reticular network.

Remarks. The Co To specimens agree well with the original description of Parasmittina parsevalioidea Liu (in Liu et al.), 2001 , from Hainan Island, China, roughly 200 km southeast of Co To. The original description notes that Parasmittina parsevalioidea varies in colony form from unilaminar to multilaminar, but we observed only the unilaminar condition in the colonies collected at Co To.

Tilbrook (2006) declared P. parsevalioidea to be a junior synonym of P. galerita Ryland & Hayward, 1992 , originally described from the Great Barrier Reef; however, while the two are very similar, they also appear to show consistent differences, and we retain the former name for populations in China and Vietnam. In P. galerita , the condyles are relatively small, blunt, and directed medially, with fine denticulation around the blunt end; in P. parsevalioidea , the condyles are long, tusk-shaped, acute, and directed proximomedially toward the lyrula, with denticulation along the curved edge. The lyrula in P. parsevalioidea appears to be wider than in P. galerita . In P. galerita , the peristome is complete around the proximal margin of the ooecium, whereas in P. parsevalioidea , short extensions of the peristome extend onto the ooecium but only occasionally meet to form a continuous peristome. Finally, the original description of P. galerita indicates that zooids have a single, ephemeral oral spine; spine number in our material ranges from one to four but most zooids have two, with spine bases remaining in older parts of the colony far from the margin. Nominal Parasmittina galerita from the Solomon Islands ( Tilbrook 2006) has blunt condyles, one or two ephemeral oral spines, giant avicularia with the distal rim coarsely toothed, one or two triangular avicularia associated with each orifice, a triangular avicularium sometimes associated with the ooecium, and a flared peristome, and may represent a distinct species—in other words, nominal P. galerita may represent a complex of closely related species.

Distribution. Previously reported from Hainan Island, China, at depths of 0–20 m ( Liu et al. 2001).

Figures

FIGURE 8. Parasmittina parsevalioidea Liu, 2001. A. Colony VNMN-0232. B. Autozooids, with small, elliptical frontal avicularia; note bases to two oral spines in many zooids, VNMN-0230. C. Autozooid (top center) with long, spatulate, proximolaterally directed avicularium originating near orifice, VNMN-0230. D. Enlargement showing sharp, tusk-like condyles, lateral-oral avicularia with triangular mandibles, and quadrate-elliptical frontal avicularia, VNMN-0234. E. Enlargement of orifice showing sharp, denticulate condyle, VNMN-0233. F. Ooecia; note acute avicularium impinging on peristome and directed toward orifice (left-center), as well as elliptical frontal avicularia. VNMN-0229. Scale bars:A, 1.0 mm; B, 250 µm; C, F, 150 µm; D, 100 µm; E, 50 µm.

FIGURE 20. Competitive interactions between bryozoans and the encrusting foraminiferan Planorbulina larvata. A. P. larvata forming stand-off with Scorpiodinipora costulata (upper part) and overgrowing the latter (lower part), VNMN-0254. B. P. larvata overgrowing Antropora minor, VNMN-0218. C. P. larvata overgrowing Torquatella imperforata, VNMN-0252. D. Founding chamber of P. larvata settled on margin of Parasmittina parsevalioidea colony, VNMN-0231. E. Stand-off between P. larvata and Scorpiodinipora costulata, VNMN-0254. F. P. larvata settled on Disporella phaohoa n. sp. colony, VNMN-0256. G. P. larvata settled on Plesiocleidochasma porcellaniforme, VNMN-0256. H. Metroperiella cotoensis n. sp. beginning to overgrow P. larvata, VNMN-0238. Scale bars: D, 150 µm; all others, 1 mm.