New species of the highly diversified Hoplias malabaricus group (Characiformes, Erythrinidae) from La Plata Basin: Another brick in the wall

Abstract

With 13 species, the genus Hoplias contains more than 75% of the diversity of the family Erythrinidae. However, cytogenetic and molecular studies strongly suggest the existence of an outstanding cryptic diversity in this genus, with more than 20 likely new species only for the H. malabaricus group. Here, we described a new species for this group, including specimens from a wide geographic coverage within La Plata Basin: Iguazu River and Urugua-í Reservoir in Argentina and upper Parana River in Brazil. Traditional taxonomic and molecular analyses were performed. The new species is diagnosed by the following combination of characters: 15–17 predorsal scales, 38–41 lateral-line scales, 10–11 premaxillary teeth; 8–10 plate-like denticulate rakers in ceratobranchial, 39–41 vertebrae, pectoral-fin length (16.24–19.58 % SL), orbital diameter (13.15–20.06 % HL), the last vertical scale row in the caudal fin forming a straight line and the last portion of the ascending process of the premaxilla with a marked ridge. A key for the species of the H. malabaricus group is provided. This work contributes to the inventory of biological diversity of the study region but also aims to accurately identify species belonging to a group with complex taxonomy.