Taxonomy, systematics and evolution
The genus Casuarius was erected by the French scientist Mathurin Jacques Brisson in his Ornithologie published in 1760. The type species is the southern cassowary (Casuarius casuarius). The Swedish naturalist Carl Linnaeus had introduced the genus Casuarius in the 6th edition of his Systema Naturae published in 1748, but Linnaeus dropped the genus in the important tenth edition of 1758 and put the southern cassowary together with the common ostrich and the greater rhea in the genus Struthio. As the publication date of Linnaeus's sixth edition was before the 1758 starting point of the International Commission on Zoological Nomenclature, Brisson and not Linnaeus is considered as the authority for the genus.
Cassowaries (from the Malay name kasuārī) are part of the ratite group, which also includes the emu, rheas, ostriches, and kiwi, and the extinct moas and elephant birds. Three extant species are recognized, and one extinct:
Most authorities consider the taxonomic classification above to be monotypic; however, several subspecies of each have been described, and some of them have even been suggested as separate species, e.g., C. (b) papuanus. The taxonomic name C. (b) papuanus may also be in need of revision to Casuarius (bennetti) westermanni. Validation of these subspecies has proven difficult due to individual variations, age-related variations, the scarcity of specimens, the stability of specimens (the bright skin of the head and neck—the basis of describing several subspecies—fades in specimens), and the practice of trading live cassowaries for thousands of years, some of which are likely to have escaped or been deliberately introduced to regions away from their origin.
Illustration of cassowary skull
The evolutionary history of cassowaries, as of all ratites, is not well known. A fossil species was reported from Australia, but for reasons of biogeography this assignment is not certain and it might belong to the prehistoric Emuarius, which were cassowary-like primitive emus.