Sponges (Demospongiae, Poecilosclerida) from New Deep-sea Frontiers in the Southwestern Atlantic: New Species, New Combinations and Taxonomic Remarks on Echinostylinos.

Echinostylinos comprises 11 species, among which a single, recently reported record for the South Atlantic. Here we propose two further new species from this ocean basin. Echinostylinos iatapiuna sp. nov. (2300‒3200 m depth, São Paulo Ridge) and Echinostylinos abyssalis sp. nov. (4008 m depth, São Paulo Ridge). The latter pushes the genus' known distribution into the abyssal zone for the first time. The morphologic variation observed in the microscleres of Echinostylinos is briefly discussed, motivating our proposal to transfer Echinostylinos glomeris (Topsent, 1904, as Esperiopsis) to Abyssocladia, a stipitate or likely so, which compound with chelae of cleistochelae morphology to point to the latter genus as its best assignment. An identification key for Echinostylinos spp. is offered (now 13). In addition, a new species of Chondrocladia is described, namely Chondrocladia (Chondrocladia) trisigmata sp. nov. (3250-3270 m depth, south of the Vitória-Trindade seamounts' chain). Finally, some biogeographic considerations are made about abyssal sponge records in the South Atlantic.