A recent scientific investigation, spearheaded by paleontologists affiliated with the University of Bristol, the University of Manchester, and the University of Melbourne, has revealed that the colossal progenitors of contemporary kangaroos possessed exceptionally strong hindlimb bones and a well-developed tendon system. This anatomical configuration was evidently sufficient to endure the biomechanical stresses associated with saltation, thereby indicating that immense stature did not inherently preclude this characteristic mode of locomotion, contrary to prior suppositions.
Simosthenurus occidentalis. Image credit: Nellie Pease / ARC CoE CABAH / CC BY-SA 4.0 Deed.
Currently, the largest extant hopping vertebrate is the red kangaroo, which typically exhibits a body mass of approximately 90 kilograms.
However, during the Pleistocene epoch, certain kangaroo species attained sizes more than double that of their modern counterparts, with some individuals potentially reaching weights of up to 250 kilograms.
For a considerable period, the scientific consensus posited that these behemoths must have relinquished saltation, as prior biomechanical analyses suggested that hopping would become mechanically untenable at body masses exceeding approximately 150 kilograms.
“Previous estimations were derived from merely extrapolating the morphology of extant kangaroos, a methodology that may have overlooked critical anatomical distinctions,” stated Dr. Megan Jones, a doctoral candidate at the University of Manchester and the University of Melbourne.
“Our discoveries underscore that these extinct creatures were not merely scaled-up versions of present-day kangaroos; rather, their skeletal and muscular architecture was fundamentally different, facilitating the management of their prodigious body mass.”
In this contemporary investigation, Dr. Jones and her research consortium meticulously examined the hindlimb skeletal elements of 94 extant specimens and 40 fossilized remains, representing a diverse array of 63 kangaroo and wallaby species. This collection notably included members of the extinct megakangaroo clade, Protemnodon, which inhabited the planet during the Pleistocene epoch, spanning a temporal range from 2.6 million to 11,700 years ago.
For each surveyed species, researchers utilized established data on body mass estimations, in conjunction with measurements of the length and diameter of the fourth metatarsal – a crucial elongated pedal bone for saltatory locomotion in extant kangaroos. These parameters were employed to compute their capacity to withstand the mechanical forces inherent in hopping.
Subsequently, the scientific team conducted a comparative analysis of the tarsometatarsal joint structures in giant kangaroos versus those of modern kangaroo species.
They proceeded to infer the requisite size of the tendons that would have been necessary to support the propulsive forces for hopping in these extinct giants, and then determined whether their calcanei (heel bones) were sufficiently developed to accommodate such expansive tendons.
The authors of the study anticipate that the metatarsal bones of all examined giant kangaroo species would have exhibited adequate robustness to bear the significant biomechanical stresses generated by hopping, and that their calcanei would have been proportionally large enough to permit the tendon widths crucial for this mode of locomotion.
Collectively, these findings suggest that the hindlimb anatomy of all giant kangaroo species provided sufficient structural integrity for them to engage in saltatory movement.
Nevertheless, the researchers propose that it is improbable that giant kangaroos exclusively utilized hopping for all forms of terrestrial movement, given that their considerable body mass would render such a gait energetically inefficient for sustained travel over extended distances.
It is noteworthy that intermittent hopping behaviors are already documented in numerous smaller extant mammalian species, including certain hopping rodents and lesser-known marsupials.
The researchers hypothesize that short, rapid bursts of hopping may have served as a crucial defensive strategy for some extinct giant kangaroo species, enabling them to evade formidable predators, such as those belonging to the extinct thylacoleonid group, commonly known as marsupial lions (Thylacoleo).
“While thicker tendons offer enhanced durability, they exhibit a reduced capacity for storing and returning elastic energy,” explained Dr. Katrina Jones, a research fellow at the University of Bristol.
“This likely resulted in giant kangaroos being slower and less energetically efficient jumpers, better adapted for brief propulsive actions rather than prolonged journeys.”
“However, hopping does not necessitate peak energy efficiency to be functionally advantageous; these animals likely employed their saltatory capabilities to traverse challenging terrain swiftly or to escape imminent threats.”
“Our findings contribute to the growing understanding that kangaroos exhibited a far greater spectrum of ecological diversity in prehistoric Australia than what is observed today. Some of these large species were likely grazers, akin to modern kangaroos, while others occupied browsing niches – an ecological role not presently filled by large kangaroos,” commented Dr. Robert Nudds, a researcher at the University of Manchester.
The corroborating evidence is published in the esteemed journal Scientific Reports.
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M.E. Jones et al. 2026. Biomechanical limits of hopping in the hindlimbs of giant extinct kangaroos. Sci Rep 16, 1309; doi: 10.1038/s41598-025-29939-7
