Prototrochus burni O’Loughlin, 2007

O’Loughlin, P. Mark, 2007, New apodid species from southern Australia (Echinodermata: Holothuroidea: Apodida), Memoirs of Museum Victoria 64, pp. 53-70 : 66

Prototrochus burni O’Loughlin sp. nov.

Figure 10e; Table 1

Material. Holotype: Eastern Australia, E Victoria, 96 km S of Point Hicks, 38°40’S, 149°17’E, 2900 m, lower continental slope, compacted clay, stn SLOPE 66, RV Franklin, G.C.B. Poore et al., 25 Oct 1988, NMV F94697 (with 2 microscope slides of wheel ossicles).

Description. Anterior body part; length 2.0 mm; calcareous ring diameter 1.0 mm; 10 peltato-digitate tentacles; calcareous ring symmetrical, 10 plates, dorsal and ventral plates subequal, radial and interradial plates with single long anterior spire, radially digitiform and distally narrowly rounded, interradially narrower and distally pointed, all plates with posterior indentations, lacking posterior projections.

Body wall ossicles massed wheels only: average (21) wheel diameter 272 μ m (range 240–336 μ m); spokes thick, average 10 per wheel (range 8–12); wheel rim slightly undulating, not angular rounded, not scalloped or straight across each tooth; wheel hubs simple, not perforated; hub diameter 56 μ m for wheel diameter 256 μ m (22%), hub diameter 80 μ m for wheel diameter 320 μ m (25%); wheel teeth subequal in size, distributed regularly around inner rim, not aligned with spokes, bluntly rounded, all pointing towards hub; small 8 spoke wheel with 32 teeth (25%), large 11 spoke wheel with 35 teeth (31%); tooth length 3 μ m for wheel diameter 30 μ m (10%), tooth length 6 μ m for wheel diameter 42 μ m (14%). Tentacles lack ossicles.

Colour. Off-white, translucent; tentacles with large brown spot distally, small pair proximally.

Distribution. Eastern Australia, E Victoria, S of Point Hicks, lower continental slope; 2900 m.

Etymology. Named for Robert Burn (Marine Research Group of Victoria; Honorary Associate of Museum Victoria), in appreciation of his decades of generous and dedicated contribution to marine research and Museum Victoria, and his invaluable service to the Marine Research Group.

Remarks. Prototrochus burni O’Loughlin sp. nov. is based on a single small part-specimen. Tentacles, calcareous ring, and wheel ossicles are all present, and adequate for a specific diagnosis. The symmetrical calcareous ring, with single long anterior projection on each plate and 10 tentacles, wheels with evenly distributed teeth pointing towards the hub, and absence of rod ossicles, identify the new species as a Prototrochus Beljaev and Mironov, 1982 . The large diameter of the wheels and high number of teeth per wheel distinguish P. burni sp. nov. from P. australis (Beljaev and Mironov) , P. staplesi sp. nov. (below) and P. taniae sp. nov. (below). In the data given by Beljaev and Mironov (1981) the “bigger” wheel diameters of the holotype of P. australis are significantly larger than for any of their other P. australis specimens. All are significantly smaller than the P. burni wheels. P. burni occurs at a significantly greater depth (2900 m) than the holotype of P. australis and the other new species (below) ( Table 1).