Giant Kangaroos Could Hop Despite Massive Size, Fossil Study Reveals
Groundbreaking research has revealed that giant kangaroos weighing up to 250 kilograms, which once roamed Australia, would probably have been capable of hopping despite their enormous size. This finding challenges long-standing debates about the mobility of these extinct relatives of modern kangaroos.
New Approach to Ancient Anatomy
Unlike previous studies that extrapolated from modern kangaroo anatomy, Dr Megan Jones from the University of Manchester and her colleagues took a novel approach. Writing in the journal Scientific Reports, the team studied fossils from various giant kangaroo species, including sthenurines—short-nosed browsing kangaroos that lived between 13 million and 30,000 years ago.
"They get up to 250kg, whereas the most we get today in the red kangaroos is 90kg at the absolute most," said Jones, highlighting the significant size difference between extinct and modern species.
Analysing Tendon and Bone Strength
The research focused on two critical components for hopping: the Achilles tendon in the ankle and the bone strength of the fourth metatarsal, the least robust bone in the hindlimb. The team examined fossils from species of Protemnodon, which lived between 5 million and 40,000 years ago, and giant Macropus, resembling larger versions of today's kangaroos.
"It's no use if their tendon is fine, but their bones are going to start breaking [if they hop]," Jones explained, emphasising the importance of both elements working in tandem.
Key Findings and Implications
The results showed that all giant kangaroos studied had fourth metatarsals strong enough to support hopping and heel bones with sufficient space for thick tendons. This counters previous suggestions that thicker tendons might have made hopping less feasible.
Jones noted that some modern hopping creatures, like kangaroo rats, have relatively thick tendons yet hop effectively to navigate terrain and escape predators. She suggested giant kangaroos might have used hopping for similar purposes, albeit less frequently or over shorter distances.
"It is entirely possible that, as well as using hopping more infrequently, or over shorter distances, the giant kangaroos may have reduced stresses by hopping more slowly," the authors added.
Broader Context and Expert Insights
Dr Gilbert Price, a palaeontologist at the University of Queensland, praised the study for its direct focus on giant kangaroo fossils. "It shows that the giant kangaroos changed their proportions in ways that made hopping mechanically possible, even if it was less efficient than in modern species," he said.
Price also highlighted the study's cautious conclusions: "It doesn't say these animals hopped across the landscape like modern red kangaroos, just that hopping wasn't off the table, and that's an important distinction."
Future Research Directions
The findings could help unravel the extinction of giant kangaroos. "If you want to understand why these animals went extinct, you first have to understand what they were actually like," Price noted. Understanding their biology and ecology is central to piecing together their fate.
While the study confirms hopping was feasible, it does not rule out other modes of movement, such as striding on tiptoes, as suggested in earlier research. "Any kangaroo is going to be using a combination of gaits, some for going slow, some for going fast," Jones concluded, underscoring the complexity of prehistoric locomotion.
