Abstract A new species of LeptophoxoidesBarnard, 1962 is described with material from the continental slope of Rio Grande do Norte state, northeastern Brazil at three different depths: 150, 400 and 2,500 meters. Leptophoxoides longisetae sp. nov. can be diagnosed and distinguished from the other two species of the genus, L. molarisBarnard, 1962 and L. marinaSenna, 2010, by the following characters: antenna 1 peduncular article 1 ventral apex weakly ensiform; maxilla 1 inner plate longer than outer; maxilliped palp article 3 with blunt and extremely protuberant apex; gnathopods 1-2 carpus almost cryptic; gnathopod 2 palm defined by a large and sharply produced palmar hump; pereopod 6 basis posterodistal corner produced as a blunt lobe; and telson with two dorsal long plumose setae on each side. This is the first record of the genus for northeastern Brazilian waters, uncovering a higher biodiversity in deep waters.

Abstract A new species of Foxiphalus Barnard, 1979 is described. The material examined was collected as part of the project “Avaliação da biota bentônica e planctônica da Bacia Potiguar e Ceará” (BPOT), off northeastern Brazilian continental slope on the state of Rio Grande do Norte at depths ranging from 135 to 283 meters. Foxiphalus potiguara sp. nov. is recognized among its congeners by: rostrum slightly exceeding the article 2 of antenna 1; lower lip outer lobes with strong shoulder cusps; maxilliped inner plate with two apical robust setae; gnathopod 2 carpus shortened; pereopod 5 basis tapering distally; and epimeral plate 3 posterior margin weakly crenulated. This is the first record of Foxiphalus for the Atlantic Ocean and we provide an amended diagnosis of the genus and an identification key to its world species. In addition, two new records of Phoxocephalidae are reported from northeastern Brazil: Heterophoxus shoemakeri Andrade & Senna, 2020 and Metharpinia dentiurosomaAlonso de Pina, 2003.

Abstract Amphipods of the family Phoxocephalidae G.O. Sars, 1891 collected by the R/V Almirante Saldanha off the coast of Uruguay and Argentina in 1972 were examined. New records from the northern Argentine Sea and Uruguayan Sea include two species of the subfamily Harpiniinae Barnard and Drummond, 1978: Pseudharpinia jonesyi Andrade and Senna, 2020a, previously known from southeast/southern Brazil; and Pseudharpinia tupinamba Senna and Souza-Filho, 2011, recorded hitherto only from southeastern Brazil. Six species of the subfamily Phoxocephalinae G.O. Sars, 1891 were also recorded: Fuegiphoxus abjectus Barnard and Barnard, 1980, Fuegiphoxus fuegiensis (Schellenberg, 1931), Metharpinia dentiurosoma Alonso de Pina, 2003b, Metharpinia grandirama Alonso de Pina, 2003b, Metharpinia protuberantis Alonso de Pina, 2001, and Parafoxiphalus longicarpus Alonso de Pina, 2001. Redescriptions and discussion on distribution and morphological variations are presented.

Abstract New records of the species Metharpinia dentiurosomaAlonso de Pina, 2003, M. grandiramaAlonso de Pina, 2003, M. iadoAlonso de Pina, 2003, Microphoxus cornutus (Schellenberg, 1931) and Mi. uroserratusBustamante, 2002 are reported for Brazilian waters. A discussion about the Metharpinia-Microphoxus complex is presented based on literature review and new observations of sampled species. Emended diagnoses are presented for the recorded species of Metharpinia and identification keys to world species of Metharpinia and Microphoxus are provided.

RESUMO Synopia ultramarina Dana, 1853 é considerada uma espécie circumtropical e foi originalmente descrita com material coletado em duas localidades, a meio caminho entre o sudoeste da África e o nordeste do Brasil. A espécie é redescrita aqui com amostras do Arquipélago de Fernando de Noronha, estado de Pernambuco, nordeste do Brasil. O material estudado foi coletado por mergulho autônomo, em camas de rodolitos, no canal Ressureta, entre as ilhas do Meio e Rata. Material adicional foi coletado ao largo da costa do estado do Ceará, durante consultorias ambientais coordenadas pela Petrobras S. A., e ao largo da costa do estado de Pernambuco, durante o Projeto REVIZEE NE IV. É apresentada discussão sobre as variações morfológicas da espécie, baseada no material estudado e em descrições prévias na literatura.

ABSTRACT Synopia ultramarina Dana, 1853 is considered a circumtropical species and was originally described based on material collected from two localities near halfway between the southwestern Africa and northeastern Brazil. The species is redescribed here with samples from Fernando de Noronha Archipelago, Pernambuco state, northeastern Brazil. The material examined was collected by SCUBA diving, from rhodolith beds, in Ressureta Channel, between Meio and Rata Islands. Additional material was collected from off Ceará state coast, during environmental consultancies, by Petrobras S. A., and off Pernambuco state coast, during the Project REVIZEE NE IV. Discussion on morphological variations of the species is presented, based on the studied material and previous descriptions in the literature.

A new amphipod species of Metharpinia Schellenberg, 1931 is described from Campos Basin, southeastern Brazilian coast. The material was collected with van Veen grab from unconsolidated substratum, off the mouth of the Paraíba do Sul River. The new species can be distinguished from its congeners by presenting a strongly constricted rostrum and a slender palp of maxilla 1. There are four species in Metharpinia from the South Atlantic: M. dentiurosoma Alonso de Pina, 2003, M. grandirama Alonso de Pina, 2003 and M. iado Alonso de Pina, 2003, and Metharpinia taylorae sp. nov. This is the first record of a species of the genus from Brazilian waters.

A new species of the amphipod family Ampithoidae Stebbing, 1899 is described from the northeastern Brazilian waters. The new described taxon is grouped in the genus Cymadusa Savigny, 1816, since it presents all the diagnostic characteristics of the genus. The examined material was collected by scuba diving in the Rocas Atoll, off Rio Grande do Norte state coast, Camamu Bay and Todos os Santos Bay, Bahia state. The new species described here is close to C. filosa Savigny, 1816, type species of the genus, by presenting anterior margin of gnathopod 1 poorly setose, male gnathopod 2 densely setose, with palmar corner not defined by a spine and dactylus subequal in length to palm, being considered part of the C. filosa complex. Among the species of this complex, the one which most resembles to the new taxon is C. imbroglio Rabindranath, 1972, which is distinguished by the absence of both the trapezoid process in the palm and spine at the palmar corner in the gnathopod 2. This is the second species of the genus Cymadusa recorded from Brazilian waters.