Antarctic holothuroids from the Bellingshausen Sea, with descriptions of new species (Echinodermata: Holothuroidea) Author O’Loughlin, Mark Author Manjón-Cabeza, Eugenia Author Ruiz, Francina Moya text Zootaxa 2009 2016 1 16 journal article 10.5281/zenodo.185959 813a57fd-0abc-4ebf-ab00-4c71ec46f634 1175-5326 185959 Psolicrux iuvenilesi O’Loughin & Manjón-Cabeza sp. nov. Figure 2a–c ; table 1. Material examined. Holotype . Antarctic Peninsula, Gerlache Strait, BENTART–2003, R/V Hesperides , stn PA23, 64.9255ºS , 63.6068ºW , 656 m , 25 Feb 2003 , MNCN 29.04/128; dorsal body ossicles slide NMV F161522; ventral body ossicles slide F161523; tentacle ossicles slide F161524. Paratypes . Type locality and date, MNCN 29.04/129 (4). Other material. Paraiso Bay, R/V Hesperides , stn BP21, 64.90ºS , 63.01ºW , 101 m , 23 Feb 2003 . Eastern Antarctica , Prydz Bay, Fram Bank, 444–453 m , 26 Feb 1991 , F68053 (1); Enderby Land, 386–400, 15 Nov 1985, F84985 (1). Diagnosis. Specimens up to 29 mm long (tentacles withdrawn), widest diameter 11 mm ; thin, flexible, calcareous, body wall with minute projecting spines; distinct sole and “belly” ventrally; oral cone, tapered anal cone forming distinct “tail”, both oral and anal cones frequently upturned; 10 subequal dendritic tentacles; large tube feet in mid-ventral and latero-ventral paired radial series defining a distinct sole with broad bare interradii; single latero-ventral row (of the paired series) bordering the bare interradii typically close, outer row of paired series more spaced; smaller tube feet scattered dorsally and laterally and on oral and anal cones; tube feet do not cross introvert; radial plates of calcareous ring elongate, sub-rectangular, with deep posterior notch; interradial plates elongate, tapered and rounded anteriorly, with shallow rounded indentation posteriorly. Ossicles in body wall numerous, imbricate, large, thick, single-layered, perforated, smooth plates with angled narrow distally spinous spire, plate and spire up to 480 µ m long, spires typically 160 µ m long; plates irregular in size and form; spired plates similar dorsally and ventrally; lacking small branched bluntly spinous rods and crosses. Largest tentacle ossicles irregularly oval to elongate, thick, knobbed, curved, perforated plates, up to 640 µ m long; smallest plates thin, smooth, marginally bluntly denticulate. Colour (preserved). Pale grey-brown. Distribution. Western Antarctica (Gerlache Strait), Eastern Antarctica (Fram Bank); 101- 656 m . FIGURE 2. a–c, Psolicrux iuvenilesi O’Loughin & Manjón-Cabeza sp. nov. : a, holotype (MNCN 20.04/128), lateral view, radial (left) and interradial plates of the calcareous ring (insert); b, spired plates (slide F161523 from holotype) and spire from body wall (slide from specimen F68053 ); c, tentacle ossicles (slide from specimen F68053 ).d, Psolicrux coatsi (Vaney, 1908) : tentacle ossicles (slide from specimen F160026).e, f, Myriotrochus hesperides O’Loughin & Manjón-Cabeza sp. nov. : e, holotype (MNCN 29.04/130), oral end with calcareous ring left, asymmetrical plates of calcareous ring (insert); f, wheels from posterior dorsal body wall (slide F161516). Etymology. From the Latin iuveniles (young people) in recognition of the skilled assistance provided by the young University of Málaga students Blanca Gallego Tevar, Carolina Yuste Florido and Juan Miguel Pérez Ramos. Remarks. O’Loughlin (2002) reviewed Psolidium (Cucumaria) coatsi Vaney, 1908 , erected the new genus Psolicrux for the species, and judged that Cucumaria conspicua Vaney, 1908 , Psolidium navicula Ekman, 1927 and Psolidium bistriatum Ludwig & Heding, 1935 were junior synonyms. Cucumaria conspicua Vaney, 1908 is removed above from the synonymy by O’Loughlin (2002) , and referred to Cucamba psolidiformis ( Vaney, 1908 ) . Body form, knobbed cross ossicles and spired plate ossicles of Psolicrux coatsi ( Vaney, 1908 ) were illustrated by O’Loughlin (2002 , figs 3c–f). In examining the material for that work it was noted that knobbed crosses were sometimes not found, and this was judged to be a sampling artefact (O’Loughlin, pers. obs.). In this work there has been a consistent absence of knobbed crosses in some specimens. The specimens lacking knobbed crosses are referred to the new species Psolicrux iuvenilesi O’Loughin & Manjón-Cabeza sp. nov. In addition to the absence of knobbed crosses, the specimens are smaller, and the largest tentacle ossicles are thick knobbed oval to elongate plates while in Psolicrux coatsi (Vaney) the largest tentacle ossicles are thick, narrow, bluntly spinous, perforated rods, up to 536 µ m long ( Figure 2 d).