Comprehensive Description

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"Osthimosia notialis sp. nov.
Plate Vg, VIa,b




HOLOTYPE: BMNH 1990.7.31.9., National Antarctic Expedition, Ross Sea


PA RATYPES: BMNH 1990.7.31.10., 'Discovery' Stn 42.


Other material: 'Discovery' Stns 167, 190, 371, 1872. National Antarctic Expedition, Ross Sea, March 1903, 3.6.1903, 6.12.1903. British Antarctic Survey, Signy Island, Normanna, E. of Outer Is., 21.2.1986




Colony forming small pisiform growths, 2-4 mm diameter, slender cylinders up to 10 mm long, or small, encrusting domes; most frequently on erect substrata including other bryozoans, cnidarians or sponge spicules. Autozooids with distinct boundaries; with convex, finely nodular frontal wall bordered by few, large, marginal pores. Primary orifice slightly longer than wide, with a deep, U-shaped proximal sinus comprising one-third its total length; condyles thickened and prominent. Peristome high, typically with well-developed lateral lobes, incorporating medio­proximally a single, relatively large, suboral avicularium with oval rostrum, proximally directed. Vicarious avicularia frequent, as long as autozooids; rostrum narrow, parallel-sided proximally, abruptly expanded to a slender spoon shape distally; palate with extensive foramen; crossbar slender, without a columella. Ovicell spherical, prominent, smooth-surfaced, with a broadly triangular area of smooth entooecium exposed frontally.




Orifice length200.15 0.005
Orifice width 200.13 0.005





Osthimosia notialis is distinguished from other Antarctic and sub-Antarctic species of Osthimosia by its relatively large, proximally directed, suboral avicularium, its slender vicarious avicularia, and by the ovicell, which has a relatively larger frontal fenestra than in other species. This rather inconspicuous species is perhaps widely distributed in Antarctic waters; the present material is from localities as far apart as South Georgia and the Ross Sea." (Hayward, 1992: 295-7)


Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© National Museum of Natural History, Smithsonian Institution

Source: Antarctic Invertebrates Website (NMNH)

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