Kangaroos didn't hop always, suggests fossil evidence-based new research

An analysis by University of Bristol and the University of Uppsala scientists showed that the extinct species of kangaroos did not hop around with its hind legs, rather used alternate methods for their commute such as walking on two or all four legs.

The researchers used fossil evidence and a new analysis of shin and ankle bone data to unveil the mystery behind the evolution of the species and how macropodoids moved around over the past 25 million years.

According to the review published by the team of scientists, the hop of famous Qantas Airlines 'flying kangaroo' that "many people regard as the pinnacle of kangaroo evolution", represents one of the many alternate ways these animals evolved to be successful in distinctive habitats.

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"In fact, modern large hopping kangaroos are the exception in kangaroo evolution," says vertebrate paleontologist Christine Janis from the University of Bristol, lead author of the study.

"Large kangaroos were much more diverse as recently as 50 thousand years ago, which may also mean that the habitat in Australia then was rather different from today."

The earliest recognized late Oligocene–middle Miocene, basal types of kangaroos, known to be existing 25 to 15 million years ago, most likely used quadrupedal bounding, climbing and slower speed hopping as their primary modes of locomotion.

The scientists examined the weight-bearing shin bones (tibia) and heel bones (calcaneus) of kangaroos to demonstrate how the hop traits transformed over time.

The research showed that the modern kangaroos' hopping was either rare or absent in all but a few lineages.

Early macropodoids, lived nearly 25–50 million years ago and were small and could bound, climb, and hop to some capacity.

"We want people to appreciate that large kangaroos were much more diverse as recently as 50,000 years ago, which may also mean that the habitat in Australia then was rather different from today. In fact, modern large hopping kangaroos are the exception in kangaroo evolution," Phys.org quoted lead author, Professor Christine Janis, from Bristol's School of Earth Sciences as saying.

Co-author Adrian O'Driscoll, a former Master's student in the Palaeobiology program at Bristol and now a Ph.D. student at the University of York said, "Especially supported by this new data is the notion of bipedal striding rather than hopping in the sthenurines, as their calcanea lack the anatomy (a long calcaneal heel) that would help resist rotational forces at the ankle experienced during hopping, and suggests a more-erect limb posture rather than the crouched posture essential for hopping."

Professor Janis concluded, "The assumption that increasing continent-wide aridity after the end of the Miocene selectively favoured hopping kangaroos is overly simplistic. Hopping is only one of many gait modes employed by kangaroos both in the past and today, and the fast endurance hopping of modern kangaroos should not be regarded as some 'evolutionary pinnacle."

"What makes modern endurance-hopping kangaroos appear so unusual is the geologically recent extinction of similar animals who moved in different ways. We are perhaps then in need of a rival Australian airline that covers shorter distances than QANTAS and boasts a novel motif of a striding sthenurine."

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