Prehistoric Australian giant kangaroos, new research

This video says about itself:

Procoptodon is a genus of giant short-faced kangaroo living in Australia during the Pleistocene epoch.

Procoptodon goliah, the largest-known kangaroo that ever existed, stood approximately 2.7 m tall and weighed about 240 kg.

Other members of the genus are smaller, however, and Procoptodon gilli is the smallest of all of the sthenurine kangaroos, standing ~1m tall.

Procoptodon goliah was mainly known for living in semiarid areas of South Australia and New South Wales. These environments were harsh, characterized by vast areas of treeless, wind-blown sand dunes.
However, the area around Lake Menindee, in western New South Wales, had a cooler, wetter climate at the time Procoptodon existed. Fossilized footprints have been found on Kangaroo Island.

Procoptodon physiology was likely similar to that of the contemporary kangaroo; however, Procoptodon goliah were characterized by their large size and were more than three times the size of the largest kangaroos today.

These animals lived alongside modern species of kangaroo, but specialized on a diet of leaves from trees and shrubs.

P. goliah were distinguishable by their flat faces and forward-pointing eyes. On each foot they had a single large toe or claw somewhat similar in appearance to a horse’s hoof.

On these unusual feet they moved quickly through the open forests and plains, where they sought grass and leaves to eat. Their front paws were equally strange: each front paw had two extra-long fingers with large claws. It is possible that they were used to grab branches, bringing leaves within eating distance.

Procoptodon goliah were unable to hop as a mode of transportation, and would have been unable to accelerate sufficiently due to their mass.

From the University of Arkansas in the USA:

Crushing bite of giant kangaroos of ice age Australia

September 11, 2019

An in-depth analysis of the skull biomechanics of a giant extinct kangaroo indicates that the animal had a capacity for high-performance crushing of foods, suggesting feeding behaviors more similar to a giant panda than modern-day kangaroo.

The new findings, published in PLOS ONE, support the hypothesis that some short-faced kangaroos were capable of persisting on tough, poor-quality vegetation, when more desirable foods were scarce because of droughts or glacial periods.

“The skull of the extinct kangaroo studied here differs from those of today’s kangaroos in many of the ways a giant panda‘s skull differs from other bears,” said Rex Mitchell, post-doctoral fellow in the Department of Anthropology at the University of Arkansas. “So, it seems that the strange skull of this kangaroo was, in a functional sense, less like a modern-day kangaroo‘s and more like a giant panda’s.”

Mitchell used computed tomography scans to create three-dimensional models of the skull of Simosthenurus occidentalis, a well-represented species of short-faced kangaroo that persisted until about 42,000 years ago. Working with the models, Mitchell performed bite simulations to examine biomechanical performance. The resulting forces at the jaw joints and biting teeth were measured, as well as stress experienced across the skull during biting.

Mitchell compared the findings from the short-faced kangaroo to those obtained from models of the koala, a species alive today with the most similar skull shape. These comparisons demonstrated the importance of the extinct kangaroo’s bony, heavily reinforced skull features in producing and withstanding strong forces during biting, which likely helped the animal crush thick, resistant vegetation such as the older leaves, woody twigs and branches of trees and shrubs. This would be quite different than the feeding habits of modern Australian kangaroos, which tend to feed mostly on grasses, and would instead be more similar to how giant pandas crush bamboo.

“Compared to the kangaroos of today, the extinct, short-faced kangaroos of ice age Australia would be a strange sight to behold,” Mitchell said.

They included the largest kangaroo species ever discovered, with some species estimated to weigh more than 400 pounds. The bodies of these kangaroos were much more robust than those of today — which top out at about 150 pounds — with long muscular arms and large heads shaped like a koala’s. Their short face offered increased mechanical efficiency during biting, a feature usually found in species that can bite harder into more resistant foods. Some species of these extinct kangaroos had massive skulls, with enormous cheek bones and wide foreheads.

“All this bone would have taken a lot of energy to produce and maintain, so it makes sense that such robust skulls wouldn’t have evolved unless they really needed to bite hard into at least some more resistant foods that were important in their diets,” Mitchell said.

The short face, large teeth, and broad attachment sites for biting muscles found in the skulls of the short-faced kangaroo and the giant panda are an example of convergent evolution, Mitchell said, meaning these features probably evolved in both animals for the purpose of performing similar feeding tasks.

Mitchell is also affiliated with the University of New England in Armidale, Australia, where he performed the analyses during his doctoral studies.