The Mid-Atlantic Ridge (MAR) divides the Atlantic Ocean longitudinally into two halves, each with a series of major basins delimited by secondary, more or less transverse ridges. Recent biological investigations in this area were carried out within the framework of the international project Mar-Eco (Patterns and Processes of the Ecosystems of the Mid-Atlantic Ridge). In 2009 (from October, 25 to November, 29) 12 benthic sampling events were conducted on the R/V Akademik Ioffe, during the first oceanographic cruise of South Atlantic Mar-Eco. As a result we report some rare Oplophoridae species collected during the cruise. This family includes 73 species occurring strictly on the meso- and bathypelagic zones of the oceans. Five Oplophoridae species were sampled: Acanthephyra acanthitelsonis Bate, 1888; A. quadrispinosa Kemp, 1939; Heterogenys monnioti Crosnier, 1987; Hymenodora glacialis (Buchholz, 1874) and Kemphyra corallina (A. Milne-Edwards, 1883). Among these, H. monnioti and K. corallina are considered extremely rare, both with very few records. Of the sampled species, only A. quadrispinosa and H. glacialis were previously recorded to southwestern Atlantic, so the Oplophoridae fauna of the South MAR seems more related with the fauna from the eastern Atlantic and Indian oceans.La Cordillera Meso-Atlántica (CMA) divide el Océano Atlántico en dos partes, cada una con varias cuencas delimitadas por cadenas de montañas transversales. Recientemente se han efectuadoinvestigaciones biológicas en esta región en el marco del proyecto internacional Mar-Eco (Patterns and Processes of the Ecosystems of the Mid-Atlantic Ridge). Entre octubre y noviembre de 2009 se obtuvo 12 muestras bentónicas durante el primer crucero oceanográfico del Mar-Eco del Atlántico Sur. Durante este crucero se encontraron algunas especies raras de la familia Oplophoridae. Esta familia incluye 73 especies que ocurren estrictamente en las zonas meso- y batipelágicas de los océanos. Se colectaron cinco especies de Oplophoridae: Acanthephyra acanthitelsonis Bate, 1888; A. quadrispinosa Kemp, 1939; Heterogenys monnioti Crosnier, 1987; Hymenodora glacialis (Buchholz, 1874) y Kemphyra corallina (A. Milne-Edwards, 1883). De éstas, H. monnioti y K. corallina son consideradas muy raras, ambas con escasos registros. Solamente A. quadrispinosa y H. glacialis se han registrado previamente en el Atlántico sudoccidental; así la fauna de Oplophoridae de la CMA Sur parece más relacionada con la fauna del Atlántico este y océano Índico.