Trochosodon aster, 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 : 169

Trochosodon aster sp. nov.

Figures 22A–C , 23

Trochosodon sp. 1 .— Cook and Lagaaij, 1976, pl. 1 figs 3, 4.

Holotype. BMNH 1976.1 .6.2 part, Challenger stn 185, Cape York , Queensland, 279 m.

Paratypes. BMNH 1976.1 .6.2. part (20 colonies) and BMNH 1969.1 .2.2 (7 colonies) . NMV F99015 , F99016 , F99017 , and F101973, same locality (7 colonies) .

Etymology. aster (L.) – a star, referring to the budding pattern.

Diagnosis and description. Colonies very small, stellate, budded in alternating zooid triads early in astogeny, orifices becoming radial later, fairly flat, but mamillate and raised centrally. Primary orifice almost circular, with a wide sinus, usually obscured by the elongated peristome, that has a pair of small, rounded, lateral avicularia. Adapical pores present, root pores lunate, rare. Calcification mamillate, on adapical and antapical surfaces.

Colony diameter up to 2 mm, height 0.3 mm, number of whorls up to 4 and 3–4 zooids per whorl.

Remarks. The colonies from Cape York are heavily calcified and often somewhat worn. They range in size from 0.25 mm to nearly 2 mm in diameter and have long marginal peristomes that bear small avicularia laterally. One colony, figured by Cook and Lagaaij (1976), shows lunate root pores among the adapical mamillae. T. aster resembles T. pacificum Lu (1991: 74 , pl. 21 fig. 4) from the South China Sea but differs in the presence of lunate root pores and minute lateral peristomial avicularia. T. aster also has some characteristics similar to those described for T. linearis from the East Indies by Harmer (1957). Two of his specimens have been examined (BMNH 1964.3.2.10, Strait of Makassar, Siboga stn 88, 1301 m, and 1964.3.2.11, the Banda Sea, stn 227, 2081 m). These are proportionally larger than T. aster , with bilabiate peristomes. One colony was figured by Harmer (1964.3.2.11, p1. 48 fig. 14, text-fig.75), who gave a very detailed description of the early astogeny. The colony has a central, rounded root pore. Canu and Bassler’s (1929) unique type specimen of T. linearis was dredged from 635 m depth, from Borneo. The description is not adequate to decide its synonymy with Harmer’s specimens, that he could not have compared with the type.

Figures

Figure 22. A–D Trochosodon aster sp. nov. A, NMV F99015, paratype, young colony showing alternating triad structure; root pores and avicularia arrowed, scale = 200 µm. B, NMV 99016, paratype, older colony, scale = 500µm. C, NMV P99017, paratype, colony showing adapical calcification, scale = 500 µm.

Figure 23. Trochosodon aster sp. nov. NMV F99015, paratype, Detail of orifice and avicularia, scale = 100 µm.