''Simosthenurus,'' also referred to as the short-faced kangaroo, is an extinct genus of megafaunal
macropods
Macropod may refer to:
* Macropodidae, a marsupial family which includes kangaroos, wallabies, tree-kangaroos, pademelons, and several others
* Macropodiformes
The Macropodiformes , also known as macropods, are one of the three suborders of the ...
that existed in
Australia
Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...
, specifically
Tasmania
)
, nickname =
, image_map = Tasmania in Australia.svg
, map_caption = Location of Tasmania in AustraliaCoordinates:
, subdivision_type = Country
, subdi ...
, during the
Pleistocene
The Pleistocene ( , often referred to as the ''Ice age'') is the geological Epoch (geology), epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fina ...
. Analysis of ''Simosthenurus'' fossils has contributed to the finding that there are three lineages of macropods:
Sthenurinae
Sthenurinae (from ''Sthenurus'', Greek for 'strong-tailed') is a subfamily within the marsupial family Macropodidae, known as 'short faced kangaroos'. No members of this subfamily are extant today, with all becoming extinct by the late Pleistocen ...
,
Macropodinae
Macropodinae is a subfamily of marsupials in the family Macropodidae, which includes the kangaroos, wallabies, and related species. The subfamily includes about ten genera and at least 51 species. It includes all living members of the Macropodid ...
, and
Lagostrophinae.
The genus ''Simosthenurus'' was among the sthenurines.
The two most documented members of the genus are ''S. maddocki'' and ''S. occidentalis'', though other species have also been discovered.
Palaeobiology
Osteological
Osteology () is the scientific study of bones, practised by osteologists. A subdiscipline of anatomy, anthropology, and paleontology, osteology is the detailed study of the structure of bones, skeletal elements, teeth, microbone morphology, funct ...
information (predominantly cave floor surface finds
) has yielded that ''Simosthenurus'' is part of the same family as that of modern
kangaroo
Kangaroos are four marsupials from the family Macropodidae (macropods, meaning "large foot"). In common use the term is used to describe the largest species from this family, the red kangaroo, as well as the antilopine kangaroo, eastern gre ...
s. However, modern kangaroos are plantigrade hoppers, using jumping as their means of locomotion, while ''Simosthenurus'' was a bipedal
unguligrade
Ungulates ( ) are members of the diverse clade Ungulata which primarily consists of large mammals with hooves. These include odd-toed ungulates such as horses, rhinoceroses, and tapirs; and even-toed ungulates such as cattle, pigs, giraffes, cam ...
, walking in a manner similar to that of
hominids
The Hominidae (), whose members are known as the great apes or hominids (), are a taxonomic family of primates that includes eight extant species in four genera: '' Pongo'' (the Bornean, Sumatran and Tapanuli orangutan); ''Gorilla'' (the east ...
.
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.
''Simosthenurus'' is a highly distinct lineage of macropods, with no living descendants. However, it is possible that their closest living cousin is the
banded hare-wallaby
The banded hare-wallaby, mernine, or munning (''Lagostrophus fasciatus'') is a marsupial currently found on the Islands of Bernier and Dorre off western Australia. Reintroduced populations have recently been established on islands and fenced ma ...
, which is now restricted to small isolated islands off the coast of Western Australia.
''S. occidentalis''
''S. occidentalis''
mtDNA
Mitochondrial DNA (mtDNA or mDNA) is the DNA located in mitochondria, cellular organelles within eukaryotic cells that convert chemical energy from food into a form that cells can use, such as adenosine triphosphate (ATP). Mitochondrial DNA ...
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.
''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.
It is thought that, by rearing up on their hind limbs and using their long arms and fingers, they could reach overhead to grasp high leaves and branches and pull them down to their mouth. They then would use their powerful jaws and striated teeth to grind the tough leaves.
''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
![Naracoorte Caves- Victoria Fossil Cave Simosthenurus occidentalis](https://upload.wikimedia.org/wikipedia/commons/c/ce/Naracoorte_Caves-_Victoria_Fossil_Cave_Simosthenurus_occidentalis.jpg)
There are several proposed causes of the extinction of ''Simosthenurus.'' The two most popular hypotheses include human involvement and climate change.
Human impact
One theory postulates that human impact caused it. There are fewer extinct megafaunal Tasmanian species compared to those of continental Australia. This is most likely due to humans arriving in mainland Australia first. The extinction of ''Simosthenurus'' may be attributable to human over-hunting or habitat alteration.
However, there is no archaeological evidence for interactions with humans, and the overlap of habitation in Australia and Tasmania of both humans and ''Simothenurus'' species, if there was one, would have been relatively short.
Climate change
Another theory is that climate change caused the extinction of this genus. The
last glacial period, popularly known as the Ice Age, has been linked with a severe reduction in several megafaunal populations, including ''Simosthenurus''.
References
{{Taxonbar, from=Q144220
Prehistoric macropods
Prehistoric mammals of Australia
Pleistocene marsupials
Prehistoric marsupial genera
Fossil taxa described in 1966