Antropora minor
Creators: name: Dick, Matthew H.
name: Ngai, Nguyen Danh
name: Doan, Hung Dinh
Publisher: name: Zenodo
Year: 2020
Subjects: Biodiversity
Taxonomy
Animalia
Bryozoa
Gymnolaemata
Cheilostomatida
Antroporidae
Antropora
Antropora minor

description: Antropora minor (Hincks, 1880)
(Figs 4 C–F; 20B)
“? Membranipora trifolium, S. Wood, var. minor ” Hincks, 1880, p. 87, pl. 11, fig. 6.
Antropora minor: Tilbrook 1998, p. 34, fig. 2A–F, and synonyms therein; Tilbrook et al. 2001, p. 41, fig. 3A; Tilbrook 2006, p. 30, pl. 4B; Dick et al. 2006, p. 2209, fig. 5A, B; Gordon et al. 2007, p. 48, fig. 1G; Taylor & Tan, 2015, p. 13, fig. 7A.
Material examined. VNMN-0217 (CT-11), VNMN-0218 (CT-20), VNMN-0219 (CT-37), VNMN-0220 (CT-47), VNMN-0221 (CT-48), VNMN-0276, (CT-52), on SEM stubs; VNMN-0222, 11 colony fragments.
Measurements. AzL, 0.28–0.40 (0.350 ± 0.034); AzW, 0.20–0.26 (0.230 ± 0.015); OpL, 0.15–0.22 (0.185 ± 0.018); OpW, 0.12–0.15 (0.133 ± 0.012) (n = 15, 1).
Description. Colony encrusting, sheet-like; initially unilaminar but becoming bi- or trilaminar as additional layers are produced, initiated by budding in frontal direction.
Zooids small, distinct, delineated by sharp groove, distal third raised, forming sharp mural rim; gymnocyst negligible, sometimes evident at proximal end of zooid; cryptocyst extensive, coarsely granulate, widest proximally, narrowing laterally, continuing around inside of raised distal rim. Opesia occupying half or more of frontal length; irregular, pear-shaped, or oval; small, smooth gymnocystal papillae occasionally present proximally or proximolaterally. Spines lacking.
Small interzooidal avicularia common in angular positions formed by zooidal intersections; on raised cystid, mandible rounded, no crossbar. Vicarious avicularia rare; only one found among all specimens examined; similar in size (0.35 × 0.21 mm) to autozooids, with raised, smooth-walled, circular mandibular part of rostrum separated from smaller, proximal, cryptocystal part by sharp, medially directed condyles.
Reproducing zooids with vestigial ooecium manifested as crescent-shaped zone of smooth, inflated calcification at proximal end of next-distal zooid; when ooecium fully developed, cap entirely covering sharp distal rim of reproducing zooid. Embryos brooded endozooidally.
Ancestrula similar to but smaller than subsequent zooids; appears to bud first daughter zooid(s) distolaterally on one or both sides, with subsequent spiral budding pattern from first daughter zooid on one side.
Remarks. Diagnostic characters for this species include the irregular occurrence of “kenozooidal papillae” at the proximal end of some zooids, and large vicarious avicularia interspersed with autozooids (Tilbrook 1998). Some zooids in our specimens have proximal papillae, but these do not appear to be kenozooidal, but rather are raised swellings in the exposed proximal gymnocyst. Some of the supposed kenozooidal papillae illustrated by Tilbrook (1998) likewise appear to be gymnocystal swellings rather than interzooids (e.g. Tilbrook 1998, fig. 2C), whereas others are ambiguous (e.g. Tilbrook 1998, fig. 2E). We observed only one vicarious avicularium, with most colonies lacking any; Tilbrook (1998) noted that vicarious avicularia may be absent from large areas of some colonies of A. minor.
Distribution. Originally described from Bahia, Brazil (Hincks 1880 b), this nominal species putatively has a circumtropical distribution in shallow shelf areas (Tilbrook 1998, 2006; Tilbrook et al. 2001). Given the improbability of connectivity between Atlantic and Pacific populations in the era preceding widespread transoceanic shipping, this species has either been widely dispersed anthropogenically over the past few centuries, or comprises a complex of morphologically similar but genetically divergent geographical clades. The closest previous records to northern Vietnam are from the Philippines, Sabah (Malaysia), and China (Tilbrook 1998, 2006).
description: Published as part of 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, pp. 201-252 in Zootaxa 4747 (2) on pages 210-211, DOI: 10.11646/zootaxa.4747.2.1, http://zenodo.org/record/3694740