Cellarinelloides megaciona, Hayward & Winston, 2011

Hayward, Peter J. & Winston, Judith E., 2011, Bryozoa collected by the United States Antarctic Research Program: new taxa and new records, Journal of Natural History 45 (37 - 38), pp. 2259-2338 : 2295-2296

Family SCLERODOMIDAE Levinsen, 1909

Cellarinelloides megaciona sp. nov.

( Figure 17 )

Material

Holotype. NMNH 1154035 : Eltanin cruise 22, station 1536, 54 ◦ 29’ to 54 ◦ 31’ S, 39 ◦ 22’ to 39 ◦ 19’ W, 659–686 m, 8 February 1966; a single colony, in four pieces, total length 51 mm.

Description

Holotype colony erect, bilaminar, with a flat, almost parallel-sided, strap-like form with almost constant width of 6 mm; slightly curved at the proximal end, otherwise practically straight. The distal edge of the colony is undamaged, but the proximal portion is missing, and the ancestrula, early ontogeny and mode of attachment are unknown. Autozooids in alternating transverse rows, continuous around edges of branch, with a row of six on each face and one on each edge. Individual autozooid boundaries discernible externally in early ontogeny but indistinct later, when entire colony has continuous, coarsely reticulate, frontal calcification; in sectional view this is c. 0.19 mm thick along the midlines of the zooids and 0.38 mm at their peripheries; viewed internally, the reticulation is seen to originate as marginal pores, and the central area of the frontal shield is imperforate. Secondary orifice of autozooid irregularly oval, thick-rimmed, with successive increments of frontal shield thickening evident as successive rims, but lacking the elaborate oral ledge and umbones characteristic of Cellarinella , although there is often a small median, proximal umbo in zooids distributed along growth checks. Every autozooid with a large adventitious avicularium, frontally situated, its rostrum immediately proximal to the secondary orifice, and occupying a similar area, slightly acute to frontal plane and directed proximally; rostrum broadly triangular, hooked apically, the palatal foramen forming a rough “W” shape, crossbar stout, with a thick, knobbly columella. No ovicells observed.

Measurements

All measurements are for n = 20, mean ± SD; aperture length 0.26 ± 0.02 mm; aperture width 0.24 ± 0.02 mm; avicularium length 0.26 ± 0.03 mm; avicularium width 0.26 ± 0.02 mm.

Etymology

Greek, megas: large, kion: pillar, with reference to the thickened columella on the crossbar of the avicularium.

Remarks

The colony is banded by assumed growth check lines, 14 in total, imparting to it an indistinctly nodulated appearance. The distal edge is smoothly rounded off, with no evidence of buds, suggesting that growth was quiescent at the time of collection. Cellarinelloides is distinguished from Cellarinella in lacking apertural avicularia, and in its comparatively simple aperture. It is otherwise known only by the genus type, C. crassus Moyano, 1970 , which develops very large (> 100 mm high) colonies, consisting of broad bilaminar plates. The secondary orifice of C. crassus is wider than long, with a prominent, medially peaked, proximal lip, and the rostrum of the avicularium is lightly calcified with a slender crossbar that lacks a columella. It is an endemic Antarctic species, described from Marguerite Bay and widely distributed in the Ross Sea, and C. megaciona sp. nov. represents the first occurrence of the genus outside the Antarctic Circle.

Figures

Figure 17. Cellarinelloides megaciona sp. nov., Holotype. (A) Autozooids at distal margin of colony; (B) detail to show two secondary orifices and two avicularia. Scale bars: 0.5 mm (A), 0.25 mm (B).