Neothyonidium, Deichmann, 1938

O’Loughlin, P. Mark, Harding 1, Caroline & Paulay, Gustav, 2016, The sea cucumbers of Camden Sound in northwest Australia, including four new species (Echinodermata: Holothuroidea), Memoirs of Museum Victoria 75, pp. 7-52 : 35

Neothyonidium (?) insolitum O’Loughlin sp. nov.

Zoobank LSID. http://zoobank.org/ urn:lsid:zoobank.org:act:

7FCA7216-B862-4A4E-A829-07CA9DC0E23D

Table 1; appendix 1; figure 21

Table 1 ; appendix 1; figures 19a–c, 20

Material examined. Holotype. Northwest Western Australia, Kimberley Region, Camden Sound , WAMSI 1.1 .1, RV Solander, sled, site no SOL_47, WAM station no 42, barcode 10002958, from -15.612805 124.073033 36 m to -15.612437 124.072883 35 m, 26 Mar 2015, WAM Z89054 .

Description. Body fusiform, cylindrical mid-body, tapered and rounded oral end, tapered anally to narrow end, live body variably 50 mm long, 13 mm diameter, body (preserved in 95% ethanol) 26 mm long, up to 14 mm diameter; complete cover of tube feet, more numerous ventrally than dorsally, tube feet diameters about 0.2 mm; tentacles in inner circle of five very small, outer circle of 13 large; calcareous ring elongate, tubular, with both radial and inter-radial plates fragmented into a mosaic of small pieces; inconspicuous anal scales detected; single polian vesicle.

Table 1; appendix 1; figure 22

Ossicles of mid-body wall numerous Thyone -like oval tables, discs with most frequently four perforations, sometimes with an additional four smaller corner perforations to create a rounded rectangular disc, discs up to 80 µm long; spires two short pillars with one distal cross-bridge, two distal splayed spines at base of each pillar, spire height about 24 µm. Tube feet endplates with variable diameters up to 224 µm, irregular perforations and margin; rare tube foot support tables with elongate discs up to 80 µm long; some tube foot support rods, similar to tentacle rods, sometimes forked distally with enlarged rounded ends with few small perforations. Peri-oral wall with tables similar to mid-body wall, but discs generally smaller, up to 55 µm long. Peri-anal body wall with tables similar to mid-body wall, but smaller as in peri-oral region; small rosettes present; anal multi-layered scales present. Tentacles with thick and thin rods, distal ends swollen with small perforations; thick rods sometimes branched distally into widened ends with small perforations, thick rods up to 160 µm long; thin rods up to 90 µm long.

Live colour off-white to grey, semi-translucent; preserved colour off-white.

Distribution. Northwest Western Australia, Kimberley Region, Camden Sound, 35– 36 m.

Etymology. From the Latin insolitum (meaning unusual), with reference to the unusual combination of characters for the genus Neothyonidium .

Remarks. We refer the new species to Neothyonidium Deichmann, 1938 on the basis of the body form, cover of tube feet, near 20 tentacles of two sizes, form of the composite calcareous ring, and body wall table ossicles with two pillars. But we do so with reservation because of the atypical combination of two morphological characters: five very small tentacles and 13 larger ones; Thyone -like table ossicles in the body wall. These two characters distinguish Neothyonidium (?) insolitum O’Loughlin from all other Neothyonidium species.