The dolphin genus Lagenorhynchus has included six species of dolphins characterized by short, wide rostra. Genetic analyses have consistently found the genus to be polyphyletic with four of the species being included in the subfamily Lissodelphininae. A recent paper synthesized available molecular, morphological and acoustic evidence to support a taxonomic revision of the genus, assigning L. obliquidens, L. obscurus, L. australis and L. cruciger to the genus Sagmatias within Lissodelphiniae. Here, we add new phylogenomic data to a previously analyzed dataset including over 3000 nuclear genes and complete mitochondrial genomes and reevaluate morphological and acoustic evidence for the phylogenetic relationships among the Lissodelphininae. We find strong molecular evidence that L. australis and L. cruciger are more closely related to the four members of the genus Cephalorhynchus than they are to L. obliquidens and L. obscurus. Independently of the molecular data, the available morphological and acoustic evidence supports these relationships. As a consequence, to achieve monophyletic taxonomic units, we propose inclusion of L. australis and L. cruciger in Cephalorhynchus. As Sagmatias australis is the type species of Sagmatias, which now falls in synonymy with Cephalorhynchus, and as there is no previous available generic name for L. obliquidens and L. obscurus, we propose a new genus for these two species, Aethalodelphis, meaning sooty or dusky dolphin.