In a new study, paleontologists from the United Kingdom and Sweden reviewed the fossil evidence of locomotion of kangaroos and their relatives (wallabies, tree-kangaroos, rat-kangaroos, etc.) over the last 25 million years. Their results indicate that the higher-speed endurance-hopping typical of modern large-bodied kangaroos was probably rare or absent in all but a few large-bodied lineages, including the direct ancestors of modern large kangaroos like red and gray kangaroos.
Macropodidae — the crown clade encompassing kangaroos, wallaroos, wallabies, pademelons, tree-kangaroos, the quokka, the banded hare-wallaby, and extinct short-faced kangaroos — constitutes the quintessential ‘eco-model’ for adaptive specialization towards higher speed endurance-hopping.
Despite the pervasive popular image of the QANTAS ‘flying kangaroo,’ the locomotory evolution of kangaroos and their more distant crown clade relatives is surprisingly diverse with documented fossil and living species evidencing a range of bipedal, quadrupedal, saltatorial, pentapedal, ambulatory, cursorial and scansorial locomotor modes, as well as burrowing behaviors developed over the last 25 million years.
The earliest recognized Late Oligocene-Middle Miocene (25 to 15 million years ago) basal types of kangaroos most likely employed quadrupedal bounding, climbing and slower speed hopping as their primary modes of locomotion.
Yet, all these early forms were small-bodied, below 12 kg, with larger bodied kangaroos over 20 kg not appearing until the Late Miocene (around 10 million years ago), coinciding with increasing aridity and the spread of openly vegetated habitats.
Hopping is functionally problematic at larger body sizes. Consequently, some members of the later kangaroo radiation achieved a more specialized anatomy for efficient higher-speed hopping at body sizes over 35 kg.
Modern large kangaroos are spectacular hoppers but none today are over 100 kg (most individuals under 70 kg)…
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