Conescharellina plana, Bock & Cook, 2004

Bock, Philip E. & Cook, Patricia L., 2004, A review of Australian Conescharellinidae (Bryozoa: Cheilostomata), Memoirs of Museum Victoria 61 (2), pp. 135-182 : 157-158

Conescharellina plana sp. nov.

Figures 10A–D

Holotype. NMV F98996 , stn SLOPE-2.

Paratypes. NMV F98997 , stn SLOPE-2 (26 colonies) .

Other specimens. NMV F101951, stn BSS-167 (4 colonies, 1 with root and ovicells); NMV F101952, stn BSS-169; 3 colonies, 1 with root); NMV F101953, stn SLOPE-6 (5 colonies); NMV F101954, stn SLOPE-7 (1 colony); NMV F101955, stn SLOPE-40 (57 colonies, 2 with roots); NMV F101956, stn SLOPE-56 (13 colonies); NMV F101957, stn GAB-020 (6 colonies); NMV F101958, stn GAB-030 (2 colonies, 1 with root); NMV F101959, stn GAB-044 (1 colony with root); NMV F101960, stn GAB-049 (1 colony).

Etymology. planus (L.) – smooth, with reference to the lack of raised peristomes above the colony surface.

Diagnosis. Conescharellina with large, slightly flattened colonies, solid antapically. Zooid orifices in radial rows, deeply sunken within a circular peristome, that is not raised above the colony surface. Avicularia paired, small, with a minute ligula. Root pores numerous, circular, surrounded by avicularia. Ovicells fragile with a fairly wide ectooecial rim.

Description. Colonies large, slightly flattened, wider than high. Zooid orifices in marked, apparently radial series, peristomes tubular, deep but not prominent at the surface. Calcification smooth to finely tuberculate. Primary orifice with a small, rounded sinus, deeply hidden at the base of the circular peristome, adapical pore just outside the edge of the peristome. Ovicells fragile, with a fairly wide ectooecial rim and a semitransparent entooecial frontal area. Avicularia paired, close to the edge of the peristome, adapical and antapical, very small, rounded, with a minute ligula. Root pores numerous, large, circular, surrounded by a circlet of 3–4 small avicularia. Antapical surface solid and flat, with small, scattered avicularia.

Colony diameter 4.5 mm, height 2 mm. Number of whorls 5, number of zooids per whorl 8.

Remarks. The large, circular root pores of C. plana are similar in appearance to those of Conescharellina eburnea , C. perculta , C. humeru s and Crucescharellina australis that are also surrounded by a circlet of small, rounded avicularia. The peristomes of C. plana are unusual in being elongated but not prominent and the colony surface is smooth. Two colonies exhibit a single, marginal zooid each, with a prominent peristomial avicularium ( Fig. 10C ). Only one of the two ovicells present in the colony from stn BSS-167 is complete; a deeply pigmented embryo is visible through the thin frontal calcification. Colonies of C. plana are widely distributed off the southern and eastern coasts of Australia occurring from the western Australian Bight to the eastern border of Victoria, through Bass Strait, from depths ranging from 80 to 1096 m.

Figures

Figure 10. Conescharellina plana sp. nov. A–C, NMV F98996, holotype. A, adapical view of colony, scale = 1 mm. B, detail of root pore with surrounding avicularia, scale = 200 µm. C, detail of colony margin showing orifices, peristomes, and avicularia, scale = 200 µm. D, NMV F98997, paratype, antapical surface of colony, scale = 500 µm.