Redefinition of <i>Stemonosudis intermedia</i> ( <scp>Ege</scp> , 1933) and description of a new species from the western Atlantic Ocean ( <scp>Aulopiformes: Paralepididae</scp> )

We examined specimens of slender barracudina in the genus Stemonosudis collected from the western Atlantic Ocean. Investigation revealed that seven specimens represent the first adult records of Stemonosudis intermedia (Ege, 1933), previously known only from juveniles. We redescribed S. intermedia based on the holotype and newly recognized adult and juvenile specimens, and using this ontogenetic series, we document changes in coloration from light-brown juveniles to black adults. We also determined that some specimens from the western Atlantic Ocean previously identified as S. intermedia represent a new species, which we describe herein based on three adults and five juvenile specimens. The new species differs from congeners by having 43-44 anal-fin rays, 117-121 total vertebrae and a pale mouth, gill chamber and gill arches, among a combination of other characters. We also provide information on the lectotype of S. similis (Ege, 1957), which remains known only from the type series.