Antropora minor (Hincks, 1880),

Judith L Winston, 2016, Bryozoa of Floridan Oculina reefs, Zootaxa 4071 (1), pp. 1-81: 20-21

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Antropora minor (Hincks, 1880)


Antropora minor (Hincks, 1880) 

( Fig. 10View FIGURE 10; Table 9)

Membranipora trifolium  var. minor Hincks, 1880: 87  , pl. 9, fig. 6.

Membrendoecium parvus Canu & Bassler, 1928 a: 61  , pl. 1, figs 1–2.

Membrendoecium minus: Marcus 1937: 50  , pl. 9, fig. 22 A, B.

Antropora minor: Tilbrook 1998: 34  , fig. 2 A –F; Vieira et al. 2008: 14; Winston et al. 2014: 151, fig. 7.

Material examined. VMNH no. 70609, 70610; USNM no. 1283235.

Description. Colonies encrusting, unilamellar, on calcareous substrata ( Fig. 10View FIGURE 10 A). Zooids oval to subtriangular, broader proximally. Frontal membrane underlain by beaded cryptocyst and rimmed by proximally elongated gymnocyst ( Fig. 10View FIGURE 10 B). Cryptocystal shelf also broader proximally, gradually narrowing to distal wall around half-moon shaped operculum and forming oval to bell-shaped opesia. Interzooidal avicularia interspersed between autozooids, each with circular foramen, granular cryptocyst and well-developed gymnocyst that may have a small tubercle ( Fig. 10View FIGURE 10 B, C); mandible U-shaped, rostral rim well calcified. Brooding zooids show thickened lunate rim of calcification distally.

`Remarks. The most unusual feature of this species is its ability to calcify over the frontal membrane and opesia of many zooids in a colony ( Fig. 10View FIGURE 10 E, F). In some zooids a small central opening may remain. In others the entire frontal surface is covered by concentric rings of calcification. These ‘closure plates’ may be a way to protect zooids from predation (colonies on Oculina  showed a considerable amount of damage and repair), or a means to preserve nutritive resources in a food-scarce habitat.

Distribution. Oculina  banks, Atlantic coast of Florida, Brazil.

TABLE 9. Measurements in mm of Antropora minor (Hincks, 1880).

Mean 0.381     0.061    
  0.040     0.008    
  0.324     0.054    
  0.450     0.072