Massinium Samyn & Thandar, 2003

Samyn, Yves & Thandar, Ahmed S., 2010, Two new species in the phyllophorid genus Massinium (Echinodermata: Holothuroidea) with redescription of Massinium magnum, Zootaxa 2399, pp. 1-19 : 2

Genus Massinium Samyn & Thandar, 2003

Diagnosis (after Samyn & Thandar, 2003, here amended). A genus of dendrochirotid holothuroids with twenty tentacles arranged in two circles of 10 + 10; anus usually encircled by calcareous teeth; calcareous ring elongate, tubular, with both radial and interradial plates fragmented into a mosaic of small pieces and prolonged posteriorly, with the posterior processes distally linked to processes of neighbouring plates forming a loop beneath the water vascular ring; Polian vesicles elongate, usually four; ossicles of body wall comprise granuliform rods and/or rosette-shaped deposits, tables present in juvenile or occasionally in adults as scarce, reduced deposits.

Type species: Massinium maculosum Samyn & Thandar 2003 (by original designation)

Remarks. The diagnosis of Massinium is here amended to also include Neothyonidium dissimilis Cherbonnier, 1988 from Madagascar. Re-examination of the holotype of the latter species revealed that its calcareous ring is inaccurately illustrated (cf. Cherbonnier 1988: 213, fig 92N) and that its structure satisfies the diagnosis of Massinium (see fig. 11). Therefore, N. dissimilis is here transferred to Massinium . However, M. dissimilis also has scarce table deposits in the body wall (cf. Cherbonnier 1988: 212, 213: fig 92A-G), reported as absent in the original diagnosis of the genus. Scarce, reduced, table-like deposits are also present in Sluiter’s (1901) complete specimens of M. magnum from Indonesia. As such, we amend the diagnosis of Massinium to also accommodate those species with table deposits in their body wall.

Since we think that the only existing specimen of M. dissimilis is a juvenile, we regard the presence of body wall tables as a juvenile feature that may persist as scarce, reduced deposits in adults of some species of Massinium , as in M. magnum .