Sclerothyone unicolumnus Thandar 2008, sp. nov.
Creators: name: Thandar, Ahmed S.
Publisher: name: Zenodo
Year: 2008
Subjects: Biodiversity
Taxonomy
Animalia
Echinodermata
Holothuroidea
Dendrochirotida
Sclerodactylidae
Sclerothyone
Sclerothyone unicolumnus

description: Sclerothyone unicolumnus sp. nov.   
Figure 7  
Diagnosis  
Perhaps a small species, holotype (juvenile) 6 mm long. Podia mostly in double rows. Posterior processes of calcareous ring about five times length of radial plates, fragmented. Polian vesicle single. Body wall tables with smooth disc, 42-53 µm, with undulating margin and perforated by four large central and usually four or more peripheral holes; spire of fused pillars, terminating in usually a tri-forked crown. Podia without spicules except for reduced end-plates. Tentacles with rods and usually smooth multilocular plates.  
Etymology The specific name refers to the fused pillars of the body wall tables.  
Material examined  
 Holotype SAM A27987, UCT Ecol. Surv., off Mossel Bay, St. SCD 150, 34 o 59' S, 22 o 18' E, 28.viii. 1960, 106 m; paratypes, SAM-A27988, same data as holotype, 2 spec.   
Description of holotype  
Specimen minute, previously dissected, calcareous ring partially damaged and few tentacles missing. Length 6 mm, width in mid-body 1.25 mm. Colour in alcohol yellowish-white. Body form straight, cylindrical, mouth and anus terminal. Tentacles perhaps 10, only six intact, large. Anus encircled by large anal papillae, anal teeth not observed. Podia restricted to ambulacra in double rows, better developed ventrally, few also scattered in dorsal interambulacra.  
Calcareous ring (Figure 7I) delicate, not tube-like, radial and interradial plates compact, meeting only at base, radial plates triangular with slightly concave posterior margin and anterior depression for radial muscle; interradial plates also triangular with deeper posterior concavity and a slight depression at anterior end; posterior processes of radial plates extremely long, about five times the length of radial plates, reaching half body length, each fragmented into a single series of elements. Polian vesicle single, elongate; stone canal not detected. Respiratory trees reaching two thirds body length poorly branched, branches few (ca. 8-10), small, sac-like, right tree slightly longer than left. Gonad absent. Retractor muscles arising from anterior third of longitudinal bands, inserting without subdivision.  
Body wall spicules scarce tables (Figure 7A, B), restricted to posterior end, with quadrangular to subcircular, smooth disc, 42-53 µm, with undulating margin, perforated by four large central holes and usually four or more peripheral ones; spire of moderate height, comprising fused pillars without perforation, terminating in usually a tri-forked, non-perforate crown, each fork often terminally bifid. Large periproctal plates also present. Podia without spicules except for reduced end-plates (ca 57 µm), with large peripheral and much smaller central holes (Figure 7D, E). Anal papillae with irregular, smooth, multilocular plates of variety of shapes and sizes (Figure 7C). Tentacles with three types of deposits: rods (58-118 µm), usually with perforated and/or digitated ends (Figure 7G); small (42-56 µm), smooth, multilocular plates with small holes (Figure 7H); and other, slightly larger (46-58 µm), multilocular, plates with large holes and central knob (Figure 7F). No deposits detected in introvert.  
Paratypes  
Both specimens minute, 4 mm x 1.5 mm and 2 mm x 1 mm. Colour and distribution of podia as in holotype. Form slightly U-shaped. Tentacles retracted, anal teeth and papillae present. Body wall spicules as wellformed tables, present throughout integument, disc 43-65 µm (mean 55 µm) with four central and 1-5 smaller peripheral holes; spire of same form as that of the holotype, 15-23 µm (mean 20 µm). Podia without deposits except for reduced end-plates, 56-64 µm (mean 60 µm).  
Distribution Mossel Bay, WCP, 106 m.  
Remarks  
 Because of the form of the calcareous ring and the lack of elongated plates in the body wall, the new species is here referred to Sclerothyone, whose diagnosis is modified to accommodate it. The absence of deposits in the podia and introvert, may be age-related, as all three specimens are juvenile. However, in the absence of regular four-holed table discs, the presence of fused pillars, tri-forked crowns with bifurcating teeth, and three types of tentacle deposits, it differs substantially from the type species, Sclerothyone velligera (Ludwig & Heding).
description: Published as part of Thandar, Ahmed S., 2008, Additions to the holothuroid fauna of the southern African temperate faunistic provinces, with descriptions of new species, pp. 1-57 in Zootaxa 1697 (1) on pages 15-16, DOI: 10.11646/zootaxa.1697.1.1, http://zenodo.org/record/5107079