Thyone fusus (Müller, 1776)

Arumugam-Moonilal, Preyan & Thandar, Ahmed S., 2023, Designation of a neotype for the dendrochirotid holothuroid, Thyone fusus (Müller) (Echinodermata: Holothuroidea: Dendrochirotida: Thyonidae), Zootaxa 5369 (4), pp. 585-590 : 587

Thyone fusus (Müller, 1776)

( Figure 1A–F )

Holothuria fusus O.F. Müller, 1776: 232 , pl. 10, figs. 5–6.

Thyone fusus Madsen, 1941: 17 , text-figs. 12–16; Madsen & Hansen, 1994: 40, fig. 5, 23–24, map 10; McKenzie, 1991: 136 (synonymy).

Thyone flexus Hodge, 1867: 44 , pl. 10, fig. 2–11.

Diagnosis (from Madsen & Hansen 1994, McKenzie 1991, amended herein)

Medium-sized species, reaching about 70 mm in length (an exceptional figure of 200 mm was reported by Mortensen (1927) but this needs verification). Body fusiform to spindle-shaped, tapering posteriorly. Colour in life greyish-white to light brown to fawn, brown in alcohol. Tube feet well developed, distributed over entire body, numerous ventrally, scattered dorsally, often with adhering sand grains or other debris.Anal teeth present. Calcareous ring long, tubular, both ring and processes sub-divided; radial plates deeply notched anteriorly, dorsal radial plates extended posteriorly before bifurcating beyond posterior border of interradial plates, posterior processes of radial plates long; interradials prolonged, two ventral ones slightly longer. Deposits of body wall 2-pillared tables, disc with four primary holes and often a few additional, smaller, peripheral holes around the primary ones; spire of moderate height, ending in inconspicuous teeth. Supporting tables of tube feet with curved disc and endplate, the latter delicate in smaller individuals. Tentacle deposits perforated rods and plates. Introvert supported by rosettes and tables with multilocular disc and a spire with or without a cross-bar..

Material examined: Four specimens, identified as T. fusus , originating from the type locality, were received on loan from the Natural History Museum, Oslo, Norway. The largest specimen was selected for dissection and ossicle study and is here designated as the neotype, while the other three were only studied for their body wall ossicles. The current material corresponds well with the descriptions of the species presented by especially Madsen (1941), Mckenzie (1991) and Madsen & Hansen (1994).

Figures

FIGURE 1. Thyone fusus (Müller). Neotype (designated herein). A. calcareous ring (ir = interradial plate; r = radial plate, labelled according to Ludwig’s system); B. tables of body wall; C. rosettes of introvert; D. supporting tables of tube feet; E. rods and plates of tentacles; F. tables of introvert, G. tables of body wall of T. flexus (reproduced from holotype slides examined at NHMUK)) (A = Scale 1; B–G = Scale 2).