Ecological and evolutionary significance of sizes of giant extinct kangaroos
Kristofer M. Helgen A B C , Rod T. Wells D , Benjamin P. Kear B C , Wayne R. Gerdtz E and Timothy F. Flannery B FA Division of Mammals, National Museum of Natural History, Smithsonian Institution, NHB 390, MRC 108, PO Box 37012, Washington, DC 20013-7012, USA.
B South Australian Museum, North Terrace, Adelaide, SA 5000, Australia.
C School of Earth and Environmental Sciences, University of Adelaide, Adelaide, SA 5005, Australia.
D School of Biological Sciences, Flinders University of South Australia, Adelaide, SA 5001, Australia.
E School of Ecology and Environment, Deakin University, Melbourne Campus, Burwood, Vic. 3125, Australia.
F Corresponding author. Email: flannery.tim@saugov.sa.gov.au
Australian Journal of Zoology 54(4) 293-303 https://doi.org/10.1071/ZO05077
Submitted: 21 December 2005 Accepted: 22 June 2006 Published: 11 August 2006
Abstract
A 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.
Acknowledgments
This paper is dedicated to the memory of the late Russell V. Baudinette. We thank Dick Tedford, Bert Roberts, Jared Diamond, Craig McGowan, Gavin Prideaux, Tomasz Owerkowicz, Phillip Matthews, Mike Bennett and two anonymous reviewers for insightful discussion and other contributions to this manuscript. We especially thank S. Ingelby and T. Ennis (Australian Museum), W. Longmore (Museum Victoria), and C. Kemper and D. Stemmer (South Australian Museum) for access to specimens under their care. John Kelly of Kangaroo Industry Australia and the staff of Southern Game Meats facilitated the acquisition of femora of red and grey kangaroos of known bodyweight. KMH was supported by fellowships from NSF and the Australian IPRS program.
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