Trochosodon diommatus, 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 : 168

Trochosodon diommatus sp. nov.

Figures 20 , 21A–C

Holotype. NMV F99012 , figured specimen, stn SLOPE-7.

Paratype. NMV F99013 , F99014 , figured specimens, stn SLOPE-7 .

Other specimens. NMV F101970, stn SLOPE-6 (4 colonies, 3 very young); NMV F101971, stn SLOPE-7 (22 colonies, 10 with roots); NMV F101972, stn SLOPE-45 (1 colony with root).

Etymology. di – two and ommatos – an eye (Gr.), referring to the paired antapical peristomial avicularia.

Diagnosis. Trochosodon with stellate, radial peristomes, calcification smooth to finely tuberculate. Zooid orifices deeply concealed, with a narrow sinus. Frontal avicularia minute; a prominent pair on the antapical surface of the marginal peristomes.

Description. Colony stellate, fairly flat, distinctly wider than high, with prominent marginal peristomes. Orifices quincuncial at first, becoming radial. Primary orifice at the base of the long, tubular but not prominent peristome, with an elongate, fairly narrow sinus and large, paired condyles. An adapical pore present on the edge of the peristome of some peripheral zooids. Avicularia single, lateral and antapical between the peristomes, rostrum semicircular, with a bar but no ligula; other small avicularia scattered. Lunate root pores frequent in the adapical region, each with a pair of avicularia laterally. Antapical surface with marginal pores and avicularia; a pair of avicularia on the antapical surface of each peristome (cf. C. ocellata and C. eburnea ).

Colony with up to 4 whorls and 4–5 zooids per whorl. Diameter up to 4.7 mm, height up to 1.5 mm.

Remarks. Ovicells have not been seen in T. diommatus but the central position of the adapical pore suggests that they would be symmetrical, like those of T. fecundus , rather than asymmetrical, as in T. asymmetricus . Several colonies from stn SLOPE- 7 have roots present; these are 0.5–1.0 mm long. T. diommatus is easily distinguished by the presence of the pair of minute avicularia on the antapical side of the marginal zooid peristomes. It resembles two other species in the presence of antapical peristomial avicularia. It differs completely from fossil C. ocellata in dimensions and arrangement of the zooid orifices, that have a longer, more acutely subtriangular sinus. It differs from C. eburnea in its long peristomes and narrow orificial sinus, as well as the form of its root pores. T. diommatus has a similar distribution to T. asymmetricus , with the addition of a record from 800 m depth off Tasmania.

Figures

Figure 20. Trochosodon diommatus sp. nov. NMV F99012, holotype. adapical view of colony showing lunate root pores, scale = 500 µm.

Figure 21. Trochosodon diommatus sp. nov. A. NMV F99012, holotype. Detail of orifices and adapical pores, scale = 200 µm. B, NMV F99013, paratype, antapical view of marginal peristomes, showing paired avicularia, scale =200 µm. C. NMV F99014, paratype, detail of peristome, orifice, and lunate root pores, scale = 200 µm.