Microporella dentilingua Tilbrook, 2006

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 : 225-227

Microporella dentilingua Tilbrook, 2006

( Fig. 11 )

Microporella dentilingua Tilbrook, 2006, p. 210 , pl. 45E–F.

Material examined. VNMN-0243 (CT-3), VNMN-0244 (CT-42), VNMN-0245 (CT-45), VNMN-0246 (CT-46), on SEM stubs; VNMN-0247, 23 dried specimens.

Measurements. AzL, 0.52–0.60 (0.567 ± 0.023); AzW, 0.32–0.46 (0.378 ± 0.041); OrL, 0.070 –0.081 (0.075 ± 0.003); OrW, 0.11–0.12 (0.116 ± 0.004); OvL, 0.21–0.32 (0.240 ± 0.026); OvW, 0.24–0.31 (0.281 ± 0.019); AvRL, 0.10–0.13 (0.117 ± 0.009); AvRW, 0.08–0.11 (0.092 ± 0.008) (n = 15, 1).

Description. Colony encrusting, unilaminar, sheet-like.

Zooids distinct, delineated by groove. Frontal wall moderately convex, with up to five small, slit-like areolae along each lateral margin; perforated over entire surface by numerous minute pseudopores; texture coarsely pustulose between pores. Orifice terminal, semicircular, broader than long; inside corners rounded, proximal margin straight, densely denticulate; orifice surrounded by smooth, raised rim. Usually three (n = 24) but occasionally two (n = 4) short, ephemeral oral spines present; if two, these placed either widely apart at distolateral corners of orifice, or closer together near midline. Ascopore rimmed; circular or wider than long, 1–1.5 ascopore lengths (including rim) distant from orificial rim; distal margin with moderately or extensively projecting lingula, leaving broadly or narrowly crescentic opening; opening finely denticulate all around.

Avicularium single, large, nearly lateral or proximolateral to ascopore, directed distolaterally. Rostrum wide, raised distally at low angle from frontal plane; crossbar complete; narrowly semicircular proximal to crossbar, forming nearly equilateral triangular distal to it; distal end hollowed to accommodate setiform distal portion of mandible; lateral flaps lacking from setiform portion.

Ooecium prominent, globose, as broad as long, texture densely pustulose, perforated by minute pseudopores; personate, with raised peristomial rim proximal and lateral to orifice; rim extends as ridge around proximal margin of ooecium, forming complete, slightly flared peristome.

Remarks. With predominantly three oral spines, the ascopore relatively close to the orifice, the denticulate proximal orificial margin, the personate ooecium, and the large single avicularium proximolateral to the ascopore, the Co To specimens well match the original description of this species ( Tilbrook 2006). One apparent difference is in the ascopore, which in many of the Co To zooids has a nearly circular outline almost completely filled by an extensive, nearly circular lingula projecting from the distal margin, leaving a narrow, distinctly C-shaped denticulate opening. However, there is intra- and intercolony variation in the ascopore in the Co To material, with some zooids having an ascopore that is broader than long, with a small lingula, leaving a wider, crescentic opening, as Tilbrook (2006, fig. 45F) illustrated for M. dentilingua . This local variation in the ascopore resembles that reported in geographically separate populations of Microporella harmeri Hayward, 1988 ( Harmelin et al. 2011, fig. 9). In fact, M. harmeri greatly resembles M. dentilingua , but differs from the latter in having the ascopore farther from the orifice, and in having the avicularian mandible asymmetrically lanceolate in shape, with wing-like lateral expansions. Tilbrook (2006) mentioned a simple setiform mandible for M. dentilingua , as was the case for the Co To specimen that retained mandibles.

Distribution. Previously known only from the Solomon Islands ( Tilbrook 2006).

Figures

FIGURE 11. Microporella dentilingua Tilbrook, 2006, A. Colony, VNMN-0243. B. Autozooids with and without ooecium, VNMN-0243. C. Enlargement showing orifice, VNMN-0243. D. Enlargement showing intact avicularium, VNMN-0276. E. Shape of avicularian mandible, VNMN-0246. F. Autozooids with weaker orificial denticulation and smaller, less-occluded ascopore, VNMN-0244. Scale bars: A, 1 mm; B, 150 µm; C–E, 100 µm; F, 250 µm.