Morphological and molecular studies have consistently suggested that Sminthopsis, as currently defined, is rendered paraphyletic by the kultarr (Antechinomys laniger). They have also suggested a sister relationship between the kultarr and the long-tailed dunnart. Based on DNA sequence data from multiple mitochondrial and nuclear gene loci we reassign the long-tailed dunnart (formerly Sminthopsis longicaudata) to Antechinomys. Although there is good evidence of genetic structure within the kultarr (A. laniger), it does not correspond to the two currently recognised subspecies, viz A. laniger laniger and A. l. spenceri. We conclude that Antechinomys consists of two species, A. laniger and A. longicaudatus, consistent with morphology. We suggest that the observed genetic and morphological variation within A. laniger merits a more thorough investigation of more samples from across its range to resolve the taxonomy.