Osteological information (predominantly cave floor surface finds) has yielded that
Simosthenurus is part of the same family as that of modern
kangaroos. However, modern kangaroos are plantigrade hoppers, using jumping as their means of locomotion, while
Simosthenurus was a bipedal
unguligrade, walking in a manner similar to that of
hominids. Although members of
Simosthenurus were no taller than most modern species of kangaroo, their robust bones, broad pelvis, long arms and short necks were unique adaptations to their browsing mode of feeding. They had single-toed hind feet had small hoof-like nails more typical of animals adapted to moving over relatively flat terrain.
S. occidentalis S. occidentalis mtDNA sequences were obtained from fossils in Tasmanian caves; the fossils yielded
radiocarbon dates between 46,000 and 50,000 years ago. The sequences obtained in this study were from fossils much older than any Australian fossils that previously yielded sequences. This holotype is fossil material preserving the left and right dentary of an adult found at
Mammoth Cave in
Southwest Australia.
Description S. occidentalis was a leaf-eating marsupial, about the size of a modern grey kangaroo, though far more robust, with adults estimated to be about 118 kg. The species has been suggested to have used a bipedal striding gait when moving slowly. This is unlike modern kangaroos, which use pentapedal motion, or 'punting', pushing off their tail and forelimbs and swinging their hindlimbs forward when moving slowly. A mid-sized species of
Simosthenurus, known as 'short-faced' kangaroos, one of several genera in a macropodid lineage that diversified in
Pliocene Australia. The mass of adults is estimated to have around 118 kilograms, standing at a similar height to larger modern roos but with a heavier and more robust body. The dentition contains molars set close to the jaw, which combined with the cranial structure, strongly indicates an animal capable of consuming tough vegetation. Modelling of the bite force and the skulls resistance to torsional forces suggests that the species was able to consume tough material, such as leaves, bark and branches, that could be torn with the claws of the long forelimbs. The diamond-like shape of the forehead and reinforced cheek bones was able to distribute the forces applied by large muscles to the rear molars at one side of the jaw, strongly suggesting that browsing habit included an ability to tear and chew hardy and fibrous material. The morphology of the skull and dentition was found to be most comparable to Asian mammal
Ailuropoda melanoleuca (panda), an animal that primarily feeds as a browser of tough plant material.
Distribution and habitat The species is represented in the records of many southern fossil sites in Australia, including Tasmania. The type locality is located in Southwest Australia, at Mammoth Cave, and evidence from another site in the southwest indicates it existed until about 42,000 years ago. Fossils assigned to the species have been obtained at sites in the Southwest, southern regions of Central Australia and the southeast of the continent. In Tasmania
S. occidentalis has been identified at fossil sites in the northeast and central regions, the species has also been found at the nearby
King Island. Their distribution in the Pleistocene is dated to late-middle to late deposits.
S. maddocki An adult
S. maddocki was smaller than
S. occidentalis, weighing only 78 kg. Like some other species from the same time period, they were apparently highly selective feeders. Local records indicate that the species was mainly located in southeastern Australia. It is uncommon to find fossils of this rare species, especially when compared to other Sthenurines. == Extinction ==