Psolus thandari Martins & Tavares 2019, sp. nov.

Psolus thandari sp. nov.

(Figs. 5–6; Table1)

Type material. Holotype, 5.7 mm (MZUSP 593), Campos Basin, southeastern Brazil, 21°41’S, 40°20’W, Campos Basin Monitoring Program coll., xii.1991 to i.1992, 44 m. Paratypes: same data as the holotype, 3 spms 4.5–5 mm (MZUSP 1634).

Type locality. Campos Basin, southeastern Brazil, 21°41’S, 40°20’W, 44m.

Distribution. Known only from the type locality.

Etymology. This species is named in honour of Prof. Ahmed Thandar, in recognition for his dedication and contributions to the taxonomy of Holothuroidea.

Diagnosis. Body elongate, low profile. Dorsum covered by multi-layered imbricating scales adorned with granules on their surface. Mouth surrounded by five to seven, triangular valves of equal size, anus surrounded by variable number of small, irregular valves not distinctive between anus and body. Calcareous ring notched only in the radial plates. Ventrolateral ambulacra with two rows each of podia in each. Dorsum with knobbed, perforated plates. Venter with knobbed as well as smooth, perforated plates. Tube feet with knobbed, perforated rods and end plate.

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Sole ossicles Knobbed plates pseudo cups Smooth plates Knobbed cups and plates Knobbed Cups and plates Smooth plates Cups (60–190 μm) Knobbed plates Knobbed buttons Reference(s) Cherbonnier, 1974 Cherbonnier, 1974 Carriol & Féral, 1985 Carriol & Féral, 1985 Hérouard, 1901, 1906 Thandar, 2009 Ludwig & Heding, 1935 Deichmann, 1948 Ludwig & Heding, 1935 Deichmann, 1948

Description. Body elongate, of low profile, 4.5–5.7 mm long up to 2.5–2.7 mm wide (Fig. 5A). Mouth surrounded by five to seven triangular valves of equal size and anus surrounded by a variable number of small and irregular valves that intergrade with surrounding scales (Fig. 5A, B). Oral teeth lacking. Demarcation between body wall scales and oral valves distinct. Anal valves and surrounding scales poorly demarcated (Fig. 5A). Dorsum with conspicuous, imbricating scales, covered with granules (Fig. 5A; 6A, B) on their surface; lacking tube feet. Marginal dorsolateral scales of the same size as dorsal scales. Sole thin, lacking scales, tube feet restricted to ventrolateral ambulacres, arranged into two longitudinal rows with inner row of large tube feet and outer series of smaller tube feet (Fig. 5C); mid-ventral rows of tube feet absent. Polian vesicles not observed. Ten dendritic tentacles, eight large and two small ventrally. Calcareous ring simple, lacking posterior processes, radial plate notched, interradial plate not notched (Fig. 5D). Dorsum with multi-perforated, knobbed plates, with small, round holes 5–20 µm in diameter, with undulating margins and irregular in outline (90–160 µm long) (Fig. 6C). Sole with similar plates (Fig. 6D, E), and smooth, perforated plates, with undulating margins and irregular in outline (90–110 µm long) (Fig. 6F). Tube feet with curved, perforated rods, knobbed margins (100–260 µm long) (Fig. 6G, H), and end plate (100–120 µm long). (Fig. 6I).

Remarks. Psolus thandari sp. nov. differs from P. vitoriae, P. antarcticus and P. patagonicus in having 6–7 oral valves instead of 5 oral valves, and in having several, inconspicuous anal valves instead of 5 conspicuous anal valves. Psolus thandari sp. nov. can be separated from P. segregratus and P. murrayi in lacking mid-ventral tube feet, present in these latter species. The new species differs from P. lawrencei in having knobbed perforated plates in the body wall, instead of cups as in P. lawrencei. It can be distinguished from P. tommasi sp. nov. by its tuberculate instead of smooth dorsal scales.