Crucescharellina australis, 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 : 174-175

Crucescharellina australis sp. nov.

Figures 26A–E

Holotype. NMV F99024 , stn SLOPE-27.

Paratypes. NMV F99025 , stn SLOPE-27 (8 colonies) .

Other specimens. NMV F101975 , stn SOELA-S 03/84/74, E. Tasmania, 320 m.

Etymology. australis (L.) – southern, referring to the distribution of the species.

Diagnosis. Crucescharellina with biserial branches; zooid orifice with a shallow sinus. Avicularia small and rounded; occasionally large, axillary spathulate. Root pores circular, placed at branch bifurcations.

Description. Colonies probably cruciform, present material with four branches. Branches biserial, bifurcating at each fourth to fifth astogenetic generation. Primary orifice with a wide, shallow sinus, and minute condyles; obscured at the base of a long peristome. These are sometimes raised antapically (i.e. towards the end of a branch) and may have 4–5 small, spinous processes on their margins. Avicularia small, rounded, near each peristome, bar without a ligula. Rare enlarged, spathulate avicularia placed in the axils between branches. Root pores regularly placed at bifurcation of branches; circular, with a distinct rim, surrounded by 3–4 small avicularia. Adapical pore within the calcification of the edge of the peristome, present in many zooids, but no ovicells seen. Antapical surface finely granular, with approximately one small rounded avicularium per zooid.

Branches 0.6 mm width, length 6 mm.

Remarks. The specimens from stn SLOPE-27 comprise nine colony fragments. The largest show evidence of having once been cruciform but only four complete branches are now present. Two colonies have enlarged, spathulate avicularia in the axil between two branches, very similar to that shown in his “ A. decussis ” by Harmer (1957, pl. 49 fig. 13). The colony structure, type and distribution of root pores, and the large avicularia of C. australis make it virtually certain that it is conspecific with some specimens of A. decussis sensu Harmer but it is distinct from T. decussis Canu and Bassler (1929) and the other species mentioned above. Some fragmentary preparations of Harmers’ Siboga material, labelled A. decussi s, from the BMNH collection, have been examined, The specimens are all slightly worn, and none possesses large avicularia. A cruciform colony and fragments from Siboga stn 211 (BMNH 1964.3.2.21, south of Celebes, 1158 m.), most closely resembles C australis . Other fragments from Siboga stn 102 (BMNH 1964.3.2.23, Sulu Archipelago, 535 m.) differ in having triserial branches and distinctly elongated avicularia near the zooid orifices. Some partially decalcified fragments from Siboga stn 221 (BMNH 1964.3.2.25, Banda Sea, 2798–3112 m.) also resemble C. australis but have raised peristomes on the antapical side of the orifices. They possess three long roots (over 20 mm), that emanate from the root pores. It is possible that Harmer’s material, identified as A. decussis , may belong to more than one species. Circular root pores surrounded by small avicularia also occur in Conescharellina eburnea , C. plana , C. perculta and C. humerus .

Figures

Figure 26. Crucescharellina australis sp.nov. A–D, NMV F99024, holotype. A, colony from adapical surface, scale = 2 mm. B, detail of branch showing orifices, avicularia and root pore (arrowed), scale = 500 µm. C, detail of root pore, scale = 200 µm. D, detail of orifice with adapical pore, direction of growth arrowed, scale = 100 µm. E, NMV F99025, paratype, large spatulate axillary avicularium, scale = 100 µm.