Evolution of hind limb proportions in kangaroos (Marsupialia : Macropodoidea)

Kangaroos (Macropodoidea: Marsupialia) are a characteristic group of Australo-New Guinean mammals that diversified during the geographic isolation of the Australian continent in the Cenozoic. They are first recorded in the Late Oligocene, although the clade diverged from other diprotodontians around 38 million years ago (mya; Westerman et al., 2002), with early forms perhaps resembling small arboreal ‘phalangerids’ (Flannery, 1982). The purpose of this study is to examine the relationship between locomotor strategy and proportional changes in the proximal limb bones and metatarsals of a range of modern and extinct macropodoids using morphometric analyses. In addition, trends in hind limb evolution through time are investigated, firstly using only observations on extant taxa and inferring ancestral conditions on dated molecular phylogenies, and secondly by adding information from the fossil record. The results suggest that incorporating fossils can drastically change inferences about past diversity and evolutionary trends

Ecological and evolutionary significance of sizes of giant extinct kangaroos

© CSIRO 2006A method, based on femoral circumference, allowed us to develop body mass estimates for 11 extinct Pleistocene megafaunal species of macropodids (Protemnodon anak, P. brehus, P. hopei, P. roechus, Procoptodon goliah, ‘P.’ gilli, Simosthenurus maddocki, S. occidentalis, Sthenurus andersoni, S. stirlingi and S. tindalei) and three fossil populations of the extant eastern grey kangaroo (Macropus giganteus). With the possible exception of P. goliah, the extinct taxa were browsers, among which sympatric, congeneric species sort into size classes separated by body mass increments of 20–75%. None show evidence of size variation through time, and only the smallest (‘P.’ gilli) exhibits evidence suggestive of marked sexual dimorphism. The largest surviving macropodids (five species of Macropus) are grazers which, although sympatric, do not differ greatly in body mass today, but at least one species (M. giganteus) fluctuated markedly in body size over the course of the Pleistocene. Sexual dimorphism in these species is marked, and may have varied through time. There is some mass overlap between the extinct and surviving macropodid taxa. With a mean estimated body mass of 232 kg, Procoptodon goliah was the largest hopping mammal ever to exist.Kristofer M. Helgen, Rod T. Wells, Benjamin P. Kear, Wayne R. Gerdtz and Timothy F. Flanner