Two new species, Psolidium nanoplax and Psolidium lonchostinum, are described from the southeastern Brazilian coast, from 44 and 200–258 meters deep, respectively. This is the first record of the genus Psolidium from Brazil. Psolidium nanoplax sp. nov. superficially resembles its Atlantic and Magellanic congeners, P. disciformis (Théel, 1886), P. dorsipes Ludwig, 1886, and P. prostratum Pawson & Valentine, 1981, but it can be readily distinguished from these by a combination of characters of the sole ossicles and by the absence of midventral tube feet. Psolidium lonchostinum n. sp. stands apart from all Atlantic and Southern Ocean species (Atlantic sector), including Psolidium nanoplax sp. nov., in having branched rods (thorn ossicles) and knobbed plates in the sole. A key and a synoptic table to all Atlantic and Southern Ocean (Atlantic sector) species of Psolidium is provided.
Echinodermata, Sea cucumber, Biodiversity, Atlantic Ocean, Southern Ocean.
