An integrative approach reveals a new species of Zoantharia (Cnidaria, Anthozoa), Terrazoanthus silveirai, in the South-western Atlantic Ocean.

The recently erected macrocnemic family Hydrozoanthidae comprises relatively few species recorded from tropical and subtropical regions. In the Atlantic Ocean, this family has been reported only from three locations: the Caribbean Sea, the Argentine continental shelf and the Cape Verde Islands. Based on a study of colonies collected during scuba diving at Alcatrazes Archipelago's main island (São Paulo State), south-eastern Brazil, a new species belonging to the genus Terrazoanthus is described as T. silveirai sp. nov. Vaga, Migotto & Kitahara. Morphological and ecological observations coupled with molecular analyses revealed a unique cnidome, a novel facultative association with sponges, and confirmed the phylogenetic position of this new species within Hydrozoanthidae. Our results represent the second record of Hydrozoanthidae and Terrazoanthus from the South-western Atlantic, expanding the sparse taxonomic knowledge of the order Zoantharia in this area. [ABSTRACT FROM AUTHOR]