Research Suggests Extinct Giant Kangaroos Were Capable of Hopping

Giant Extinct Kangaroos Anatomically Capable of Hopping, New Study Reveals

A new study indicates that several species of giant extinct kangaroos, some weighing up to 250 kilograms, possessed the anatomical capabilities for hopping. This finding challenges previous scientific assumptions that hopping would not be mechanically feasible for kangaroos beyond a certain body size.

Background on Extinct Kangaroos

During the Pleistocene epoch, Australia was home to various large kangaroo species that significantly surpassed the size of modern kangaroos, such as the red kangaroo, which typically weighs approximately 90 kilograms. These extinct species included:

• Sthenurine: Short-nosed, browsing kangaroos that existed from 13 million to 30,000 years ago, weighing up to 250 kg.
• Protemnodon: Longer-faced animals present from 5 million to 40,000 years ago.
• Giant Macropus: Larger relatives of contemporary kangaroos.

Earlier theories, often based on extrapolations from modern species, suggested that kangaroos exceeding approximately 150 kilograms would have adopted slower gaits like walking, deeming hopping mechanically impossible due to the potential stresses on their limbs.

Study Methodology and Findings

The groundbreaking research was conducted by a team from the University of Manchester, the University of Bristol, and the University of Melbourne, with its findings published in the journal Scientific Reports.

Lead researcher Dr. Megan Jones, a postgraduate researcher at the University of Manchester, noted that the study directly analyzed fossil evidence rather than solely scaling up modern kangaroos, potentially overlooking key anatomical distinctions.

The research involved a comprehensive analysis:

• Detailed measurements of hindlimbs from 94 modern and 40 fossil specimens, covering 63 kangaroo and wallaby species, including the extinct giant kangaroo group Protemnodon.
• Examination of the fourth metatarsal bone, an elongated foot bone crucial for hopping and considered a key indicator of hindlimb strength.
• Assessment of heel bone structures to estimate the necessary tendon size and confirm if heel bones could accommodate them.

The study's findings indicated that all giant kangaroo species examined possessed fourth metatarsals robust enough to withstand the stresses of hopping. Their heel bones were also broad, providing sufficient space to anchor the thick ankle tendons required for storing and releasing energy during hopping. Researchers concluded that these anatomical adaptations suggest giant kangaroos were structurally adapted to their enormous size.

Characteristics of Giant Kangaroo Locomotion

While capable of hopping, researchers suggest that the movement of giant kangaroos likely differed from that of modern red kangaroos.

Dr. Katrina Jones from the University of Bristol highlighted that thicker tendons, while providing safety, tend to store less elastic energy. This would have resulted in slower and less efficient hopping compared to modern species.

Therefore, it is proposed that:

• Hopping was likely used for short, rapid bursts of movement.
• Such bursts could have aided in navigating difficult terrain or evading predators, such as the extinct marsupial lions (Thylacoleo).
• Hopping was probably not their primary mode for prolonged distances or long-distance travel, given its inefficiency for larger body sizes over extended periods.
• Slower hopping might have reduced stress on their anatomy.
• Fossil evidence also suggests a diverse range of movement strategies, potentially combining hopping with upright walking or quadrupedal movement.

Dr. Robert Nudds of the University of Manchester added that these findings support the idea of greater ecological diversity among prehistoric Australian kangaroos. He noted that some large extinct species functioned as grazers and others as browsers, occupying ecological niches that are not present among large kangaroos today. Dr. Gilbert Price, a palaeontologist not involved in the study, underscored its importance for its direct use of giant kangaroo fossils, demonstrating the mechanical feasibility of hopping even if less efficient than in modern species.