The genus Leuckart, 1849 (Annelida, Thelepodidae) in Brazil, with a redescription of the holotype of (Quatrefages, 1866).

The genus Thelepus Leuckart, 1849 is well known in Brazilian waters, from a species recorded by several authors as T. setosus (Quatrefages, 1866), which is considered to be a cosmopolitan species. However, the type locality of T. setosus is in France, which renders the presence of this species in Brazilian waters rather unlikely. The wide range of distribution of T. setosus is most likely due to misidentifications, especially because the original description of the species is very brief and does not include several characters now relevant at species level. We provide herein a redescription of the holotype of T. setosus and describe two new species from Brazilian material previously identified as belonging to that species. Thelepus megalabiatum n. sp. is characterised by having an expanded lower lip extending ventrally, many branchial filaments, originating from swollen cushions, with wide mid-dorsal gap between filaments within pairs, 26-33 segments with glandular areas, and 44-61+ pairs of notopodia. Thelepus brevitori n. sp. is characterised by having fewer branchial filaments, originating directly from the body wall, about 17 segments highly glandular ventrally, and up to 27 pairs of notopodia. Both new species are compared to the most similar congeners, including T. setosus.