Crucescharellina Silén, 1947

Bock, Philip E. & Cook, Patricia L., 2004, A review of Australian Conescharellinidae (Bryozoa: Cheilostomata), Memoirs of Museum Victoria 61 (2), pp. 135-182 : 173-174

Crucescharellina Silén, 1947

Crucescharellina Silén, 1947: 44 .

Agalmatozoum Harmer, 1957: 757 .

Type species. Crucescharellina japonica Silén, 1947 (original designation).

Description. Colonies are cruciform or star-shaped and may have branches that bifurcate terminally. The adapical zooid orifices are sinuate and interspersed with lunate or rounded root pores. The antapical growing edges are positioned at the limits of the branches but an antapical surface, that is the equivalent of the exposed frontal wall of conescharelliniform colonies, is also continuous and present on the “lower, non-orificial side” of colonies. It is inferred that the colonies live, in fact, with this antapical surface upward with the orifices directed downward, because the rhizoids that occur among them are inferred to anchor the colonies above or into the surface of the bottom sediments. Rounded or acute avicularia occur, that are occasionally large and spathulate. The orifices possess an adapical pore but ovicells have not been seen. Roots were figured in C. japonica by Silén (1947: pl. 1 fig. 11) and the position of the root pores suggests that the mode of life is similar to that inferred for the genus Euginoma ( Hayward 1978) , that also occurs from abyssal depths ( d’Hondt and Schopf,1984).

Remarks. Crucescharellina was introduced by Silén (1947) for C. japonica from near the Goto Islands, Japan, from a depth of 175 m. Only one colony was found; it was stellate but each branch originated from a narrow neck, one or two zooids in width. The branches rapidly expanded and then bifurcated, each subbranch starting with one or two zooids. The subbranches also expanded rapidly, so that within two as togenetic generations, the segments were 4 zooids wide. Lunate root pores were present but these were not associated with branch bifurcations and no large, spathulate avicularia were described. Gordon and d’Hondt (1997: 73, figs 221–223) described “ C. japonica ” from the Philippines from 640– 668 m. They too, had only one colony. It differed in having much less expanded branches, regular lunate root pores, and rare large axillary avicularia. The primary orifice had a shallow sinus and paired condyles. Silén (1947: 44) stated that he referred Trochosodon decussis Canu and Bassler (1929: 495 , pl. 71 figs 7–10, from 456 m, east of Mindanao in the Philippines) to his genus Crucescharellina . Harmer (1957) was unaware of Silén’s work, that was not available to him during the war of 1939–1945, and introduced Agalmatozoum for Trochosodon decussis Canu and Bassler (1929) . Colonies of this species were cruciform, with triserial branches, and were described with lunate root pores and an elliptical secondary orifice. Avicularia or small pores were present antapically but no large avicularia were mentioned in the original description. Harmer (1957) listed more than ten colonies of A. decussis from seven localities in the Sulu, Banda, and Celebes Seas. The depths were nearly all abyssal, ranging from 535 to 3112 m. The branches of the colonies were mostly biserial and the root pores were circular, placed regularly at bifurcations, and surrounded by a ring of small avicularia. In addition, large, axillary spathulate avicularia sometimes occurred on the lateral sides of branches. The species from the Siboga area described by Harmer (1957) as A. decussis strongly resembles Crucescharellina australis from Australia described below, not the original form from the Philippines described by Canu and Bassler (1929). Gordon and d’Hondt (1997: 74, figs 224–227) introduced another very similar stellate species, C. aster , with biserial branches, from several New Caledonian and New Zealand localities at a depth range of 760 to 1573 m. The root pores were central and rounded but no large avicularia were present. Their material included numerous colonies, that they noted resembled “clusters of snowflakes”. A single preparation of a colony in the Natural History Museum collection ( BMNH 1963.8.18.18) closely resembles the description of C. aster but has slightly more extended, spiny peristomes. The specimen is from Challenger stn 169, off New Zealand (37°34'S, 179°22'E, 1295 m), a station that was not mentioned by Busk (1884). Gordon (1989: 84, pl. 1E figs 50B–E) described another biserial species, C. jugalis , from northern New Zealand, from a depth range of 1217–1357 m. The colonies were irregularly branched but had circular root pores very similar to those of the Australian C. australis and A. decussis sensu Harmer (1957) .

Although there is no doubt of the synonymy of the two genera Crucescharellina and Agalmatozoum , there are uncertainties as to the identity of the various taxa referred to them in these previous descriptions. Among other records, Cook (1981) figured one of two very young, cruciform colonies from Cape York, from 279 m ( BMNH 1976.1.6.2, part), as Agalmatozoum species. These, with the specimens of C. australis described here from Point Hicks, Victoria and from eastern Tasmania, remain the only records of Crucescharellina from Australian waters to date.

Labracherie and Sigal (1975) mentioned a form similar to Crucescharellina obtained from Lower Eocene samples collected from a deep-sea drilling south of Madagascar (33°37.21'S, 45°09.60'E, 1030 m). This was not described further but is not too remote from the Recent south-west Indo- Pacific records and, unlike the European Eocene species mentioned above, may represent an early form of Conescharellinidae .