Trypostega henrychaneyi 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 : 214

Trypostega henrychaneyi Tilbrook, 2006

( Fig. 6 A–D)

Trypostega henrychaneyi Tilbrook, 2006, p. 110 , pl. 19D–F, and synonyms therein.

Trypostega henrychaneyi: Gordon et al. 2007, p. 49 , fig. 2E.

Material examined. VNMN-0225 (CT-43), on SEM stub.

Measurements. AzL, 0.34–0.49 (0.402 ± 0.045); AzW, 0.19–0.29 (0.242 ± 0.033) (n = 10, 1). OrL, 0.061 – 0.101 (0.080 ± 0.011); OrW, 0.059 –0.101 (0.075 ± 0.011); distal zooeciule L, 0.059 –0.226 (0.085 ± 0.032); distal zooeciule W, 0.059 –0.226 (0.093 ± 0.054) (n = 12, 1). OvL, 0.226; OvW, 0.213 (n = 1).

Description. Colony unilaminar, encrusting, sheet-like.

Autozooids spindle-shaped, delineated by shallow groove, boundaries often unclear due to low relief of zooids. Frontal wall only slightly convex, often with faint transverse striation, with approximately 50 to 80 circular, evenly spaced pseudopores. Orifice flush with frontal surface, pear-shaped, longer than wide, anter separated from poster by sharp, proximomedially directed condyles; poster tripartite, with lateral indentations just proximal to condyles.

Zooeciule distal to each autozooid and possibly each ooecium; small, irregularly quadrate, often not much larger than area of orifice, with small, circular orificial opening and several pseudopores.

Only one ooecium observed; longer than broad, perforated over entire surface by pseudopores of same size and spacing as on frontal wall.

Remarks. This species is identified by the pear-shaped orifice with a relatively narrow, tri-partite poster, and relatively small zooeciules. Tilbrook’s (2006) original description indicates more numerous (80–100), somewhat smaller pseudopores in the frontal wall than in the Co To specimen (50–80), although variation is evident even between the two images of complete zooids he shows for this species. In addition, zooids in the Co To specimen have the orificial poster narrower than indicated in the original description, although some zooids at Co To have a wider poster. Finally, average zooid size in the Co To specimen is somewhat smaller than in the original description (0.40 × 0.24 mm, compared to about 0.48 × 0.28 mm).

Distribution. Tropical Pacific, from Panama westward to the Great Barrier Reef, New Guinea, Torres Strait, Sulu Archipelago, and Red Sea ( Tilbrook 2006); Bangladesh ( Gordon et al. 2007); Vietnam.

Figures

FIGURE 6. A–D. Trypostega henrychaneyi Tilbrook, 2006, VNMN-0225. A. Autozooids and distal zooeciules. B. Zooid with ooecium (right). C. Enlargement showing orifice and zooeciule. D. Colony margin, showing zooeciule extending to basal surface. E, F. Exechonella similis Cáceres-Chamizo, Sanner, Tilbrook & Ostrovsky, 2017, VNMN-0226. E.Autozooids. F. Enlargement showing orifices. Scale bars: A, 200 µm; B, C, 50 µm; D, 100 µm; E, 500 µm; F, 150 µm.