Revision of Oligo-Miocene kangaroos, Ganawamaya and Nambaroo (Marsupialia: Macropodiformes, Balbaridae)

Abstract

The generic and specific status of fossil kangaroo specimens attributed to Nambaroo and Ganawamaya from the Riversleigh World Heritage Area, Australia, are revised and new material is described. Results indicate that the previously proposed 12 species (eight of Nambaroo and four of Ganawamaya) represent four species from a single genus (Ganawamaya). Previous studies distinguished species of Ganawamaya from Nambaroo in lacking a protostylid on the lower first molar. However, our analyses indicate that the apparent presence/absence of the protostylid is related to the degree of dental wear, being totally worn in older individuals. Unworn specimens from Riversleigh were previously typically attributed to Nambaroo, while worn specimens were most commonly attributed to Ganawamaya. With support from phylogenetic analyses, we refer Riversleigh's N. couperi and N. gillespieae to Ganawamaya. The diagnoses of both genera are revised. We also assign undescribed specimens from the Ngapakaldi Quarry and Leaf Locality, South Australia, to Gan. couperi comb.