Molecular evidence (28S DNA) has suggested that Triplotaenia undosa from macropodid marsupials is a species complex. Additional data (cox 1) presented in this study confirmed the hypothesis and a morphological examination of all available specimens identified a new species, T. macropodis sp. nov., in the grey kangaroos Macropus fuliginosus and M. giganteus as well as the tammar wallaby, Notamacropus eugenii, and the red kangaroo, Osphranter rufus. The new species differs in the ratio of the number of testes to the number of female genital complexes. Specimens of T. undosa from the swamp wallaby, Wallabia bicolor, the type host, and the common wallaroo, Osphranter robustus, are each genetically distinct, but the fixed material from O. robustus is too fragmentary to permit a detailed morphological description. An amended description and new illustrations of T. undosa from W. bicolor are provided.
