Simosthenurus

Last updated

Simosthenurus
Temporal range: Pleistocene
Simosthenurus AMNH.jpg
S. occidentalis skeleton at American Museum of Natural History
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Infraclass: Marsupialia
Order: Diprotodontia
Family: Macropodidae
Genus: Simosthenurus
Tedford, 1966
Species

S. maddocki
S. occidentalis
S. antiquus
S. baileyi
S. brachyselenis
S. eurykaphus
S. pales
S. tirarensis
S. orientalis

Contents

Simosthenurus, also referred to as the short-faced kangaroo, is an extinct genus of megafaunal macropods that existed in Australia, specifically Tasmania, during the Pleistocene. Analysis of Simosthenurus fossils has contributed to the finding that there are three lineages of macropods: Sthenurinae, Macropodinae, and Lagostrophinae. [1] 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

Restoration of S. occidentalis Simosthenurus BW.jpg
Restoration of S. occidentalis

Osteological information (predominantly cave floor surface finds [1] ) has yielded that Simosthenurus is part of the same family as that of modern kangaroos. [2] 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. [3] 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. [4] 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, which is now restricted to small isolated islands off the coast of Western Australia. [5]

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. [1]

The type specimen was collected by E. A. Le Souef and noted in a report to the state's Caves Board, then revised and published by Ludwig Glauert as Sthenurus occidentalis in 1910. [6] This holotype is fossil material preserving the left and right dentary of an adult found at Mammoth Cave in Southwest Australia. [6] The specific epithet occidentalis, meaning "of the west", refers to the discovery of this species in Western Australia. [7]

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. [1] 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. [4]

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. [7] The short jaw and facial anatomy clearly distinguishes their appearance from the surviving lineage of kangaroos, which usually graze on grasses rather than a browsing diet, and more closely resembles the habits of the modern koala Phascolarctos cinereus . [8]

A set of powerful molars located close to the hinge of jaw, similar to but further back than a koala, improved the mechanical advantage and a potential enlargement of the zygomaticomandibularis muscles would have reduced the hazard of dislocation while biting with the rear molars. [8] 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. [9]

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. [8] 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. [7]

Their distribution in the Pleistocene is dated to late-middle to late deposits. [7]

S. maddocki

An adult S. maddocki was smaller than S. occidentalis, weighing only 78 kg. [1] 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

S. occidentalis skeleton, Victoria Fossil Cave Naracoorte Caves- Victoria Fossil Cave Simosthenurus occidentalis.jpg
S. occidentalis skeleton, Victoria Fossil Cave

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. [10] 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. [11]

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. [12]

Related Research Articles

<i>Diprotodon</i> Extinct marsupial genus

Diprotodon is an extinct genus of marsupial from the Pleistocene of Australia containing one species, D. optatum. The earliest finds date to 1.77 million to 780,000 years ago but most specimens are dated to after 110,000 years ago. Its remains were first unearthed in 1830 in Wellington Caves, New South Wales, and contemporaneous paleontologists guessed they belonged to rhinos, elephants, hippos or dugongs. Diprotodon was formally described by English naturalist Richard Owen in 1838, and was the first named Australian fossil mammal, and led Owen to become the foremost authority of his time on other marsupials and Australian megafauna, which were enigmatic to European science.

<span class="mw-page-title-main">Mammoth</span> Extinct genus of mammals

A mammoth is any species of the extinct elephantid genus Mammuthus. They lived from the late Miocene epoch into the Holocene until about 4,000 years ago, with mammoth species at various times inhabiting Africa, Asia, Europe, and North America. Mammoths are distinguished from living elephants by their spirally twisted tusks and in at least some later species, the development of numerous adaptions to living in cold environments, including a thick layer of fur.

<span class="mw-page-title-main">Megafauna</span> Large animals

In zoology, megafauna are large animals. The precise definition of the term varies widely, though a common threshold is approximately 45 kilograms (99 lb), with other thresholds as low as 10 kilograms (22 lb) or as high as 1,000 kilograms (2,200 lb). Large body size is generally associated with other traits, such as having a slow rate of reproduction and, in large herbivores, reduced or negligible adult mortality from being killed by predators.

<span class="mw-page-title-main">Macropodidae</span> Family of marsupial mammals

Macropodidae is a family of marsupials that includes kangaroos, wallabies, tree-kangaroos, wallaroos, pademelons, quokkas, and several other groups. These genera are allied to the suborder Macropodiformes, containing other macropods, and are native to the Australian continent, New Guinea and nearby islands.

<span class="mw-page-title-main">Banded hare-wallaby</span> Species of marsupial

The banded hare-wallaby, mernine, or munning 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 mainland sites, including Faure Island and Wadderin Sanctuary near Narembeen in the central wheatbelt.

<span class="mw-page-title-main">Australian megafauna</span> Large animals in Australia, past and present era

The term Australian megafauna refers to the megafauna in Australia during the Pleistocene Epoch. Most of these species became extinct during the latter half of the Pleistocene, and the roles of human and climatic factors in their extinction are contested.

<i>Gigantopithecus</i> Genus of primate

Gigantopithecus is an extinct genus of ape that lived in southern China from 2 million to approximately 300,000-200,000 years ago during the Early to Middle Pleistocene, represented by one species, Gigantopithecus blacki. Potential identifications have also been made in Thailand, Vietnam, and Indonesia. The first remains of Gigantopithecus, two third molar teeth, were identified in a drugstore by anthropologist Ralph von Koenigswald in 1935, who subsequently described the ape. In 1956, the first mandible and more than 1,000 teeth were found in Liucheng, and numerous more remains have since been found in at least 16 sites. Only teeth and four mandibles are known currently, and other skeletal elements were likely consumed by porcupines before they could fossilise. Gigantopithecus was once argued to be a hominin, a member of the human line, but it is now thought to be closely allied with orangutans, classified in the subfamily Ponginae.

<span class="mw-page-title-main">Columbian mammoth</span> Extinct species of mammoth that inhabited North America

The Columbian mammoth is an extinct species of mammoth that inhabited North America from southern Canada to Costa Rica during the Pleistocene epoch. The Columbian mammoth descended from Eurasian steppe mammoths that colonised North America during the Early Pleistocene around 1.5–1.3 million years ago, and later experienced hybridisation with the woolly mammoth lineage. The Columbian mammoth was among the last mammoth species, and the pygmy mammoths evolved from them on the Channel Islands of California. The closest extant relative of the Columbian and other mammoths is the Asian elephant.

<i>Megaladapis</i> Extinct genus of lemurs

Megaladapis, informally known as the koala lemur, is an extinct genus of lemurs belonging to the family Megaladapidae, consisting of three species that once inhabited the island of Madagascar. The largest measured between 1.3 to 1.5 m in length.

<i>Procoptodon</i> Extinct genus of marsupials

Procoptodon is an extinct genus of giant short-faced (sthenurine) kangaroos that lived in Australia during the Pleistocene Epoch. P. goliah, the largest known kangaroo species that ever existed, stood at about 2 m (6.6 ft). They weighed about 200–240 kg (440–530 lb). Other members of the genus were smaller, however; Procoptodon gilli was the smallest of all of the sthenurine kangaroos, standing approximately 1 m tall.

<span class="mw-page-title-main">Sthenurinae</span> Extinct subfamily of marsupials

Sthenurinae is a subfamily within the marsupial family Macropodidae, known as short-faced kangaroos or sthenurine kangaroos. No members of this subfamily are extant today, with all becoming extinct by the late Pleistocene. Procoptodon goliah, the largest macropodid known to have existed, was a sthenurine kangaroo, but sthenurines occurred in a range of sizes, with Procoptodon gilli being the smallest at the size of a small wallaby.

<i>Palorchestes</i> Extinct genus of marsupial

Palorchestes is an extinct genus of large terrestrial, herbivorous Australian marsupial of the family Palorchestidae, living from the Miocene through to the Late Pleistocene. Like other palorchestids, it had highly retracted nasal region suggesting that it had a prehensile lip, as well as highly unusual clawed forelimbs that were used to grasp vegetation.

<i>Platygonus</i> Extinct genus of mammals

Platygonus is an extinct genus of herbivorous peccaries of the family Tayassuidae, endemic to North and South America from the Miocene through Pleistocene epochs, existing for about 10.289 million years. P. compressus stood 2.5 feet tall.

<i>Sthenurus</i> Extinct genus of marsupials

Sthenurus is an extinct genus of kangaroos. With a length around 3 m (10 ft), some species were twice as large as modern extant species. Sthenurus was related to the better-known Procoptodon. The subfamily Sthenurinae is believed to have separated from its sister taxon, the Macropodinae, halfway through the Miocene, and then its population grew during the Pliocene.

<i>Protemnodon</i> Extinct genus of marsupials

Protemnodon is an extinct genus of megafaunal macropodids that existed in Australia, Tasmania, and New Guinea in the Pliocene and Pleistocene. Members of this genus are also called giant kangaroos.

<span class="mw-page-title-main">Late Pleistocene extinctions</span> Extinctions of large mammals in the Late Pleistocene

The Late Pleistocene to the beginning of the Holocene saw the extinction of the majority of the world's megafauna, which resulted in a collapse in faunal density and diversity across the globe. The extinctions during the Late Pleistocene are differentiated from previous extinctions by its extreme size bias towards large animals, and widespread absence of ecological succession to replace these extinct megafaunal species, and the regime shift of previously established faunal relationships and habitats as a consequence. The timing and severity of the extinctions varied by region and are thought to have been driven by varying combinations of human and climatic factors. Human impact on megafauna populations is thought to have been driven by hunting ("overkill"), as well as possibly environmental alteration. The relative importance of human vs climatic factors in the extinctions has been the subject of long-running controversy.

<span class="mw-page-title-main">Fossil Cave</span> Flooded cave in the Limestone Coast area of South Australia

Fossil Cave (5L81), formerly known as The Green Waterhole, is a cave in the Limestone Coast region of south-eastern South Australia. It is located in the gazetted locality of Tantanoola about 22 kilometres north-west of the city of Mount Gambier, only a few metres from the Princes Highway between Mount Gambier and Millicent. It is popular with cave divers and is notable for being both a unique paleontological site and the "type locality" for very rare crustaceans which to date have been found only in caves and Blue Lake in the Mount Gambier region.

Vombatus hacketti, Hackett's wombat, is an extinct species of wombat that lived in Southwest Australia during the Late Pleistocene. It survived until very recently, going extinct between 10,000 and 20,000 BP.

<i>Bohra</i> (mammal) Extinct genus of marsupials

Bohra is an extinct genus of macropod from the Plio-Pleistocene of Australia. It is closely related to modern tree kangaroos (Dendrolagus), and like them is thought to have had an arboreal lifestyle, with some species of Bohra substantially exceeding living tree kangaroos in size.

<i>Congruus</i> Extinct genus of macropod

Congruus is an extinct genus of macropod known from the Late Pleistocene of Australia. There are two species, Congruus kitcheneri, which was originally described as a species of Wallabia, and Congruus congruus. Specimens are known from Mammoth Cave, Western Australia, the Thylacoleo Caves and the Naracoorte caves in South Australia. Potential material is also known from Eastern Australia. The morphology of the skull and limbs suggests that they were semi-arboreal browsers, moving slowly through trees, though they were larger than and not as specialised for climbing as living tree kangaroos. They are thought to be members of the tribe Macropodini, and close relatives of the extinct genus Protemnodon.

References

  1. 1 2 3 4 5 Llamas; et al. (2014). "Late Pleistocene Australian Marsupial DNA Clarifies the Affinities of Extinct Megafaunal Kangaroos and Wallabies". Molecular Biology and Evolution. 32 (3): 574–584. doi: 10.1093/molbev/msu338 . PMID   25526902.
  2. Prideaux, Gavin J.; Warburton, Natalie M. (2010). "An osteology-based appraisal of the phylogeny and evolution of kangaroos and wallabies (Macropodidae: Marsupialia)". Zoological Journal of the Linnean Society. 159 (4): 954–987. doi: 10.1111/j.1096-3642.2009.00607.x .
  3. Janis, CM; Buttrill, K; Figueirido, B (2014). "Locomotion in Extinct Giant Kangaroos: Were Sthenurines Hop-Less Monsters?". PLOS ONE. 9 (10): e109888. Bibcode:2014PLoSO...9j9888J. doi: 10.1371/journal.pone.0109888 . PMC   4198187 . PMID   25333823.
  4. 1 2 "Extinct Animals- Simosthenurus occidentalis". www.parks.sa.gov.au. Archived from the original on September 5, 2007. Retrieved 2015-10-29.
  5. "DNA Sheds Light on Mysterious Giant Kangaroo" . Retrieved 2015-10-29.
  6. 1 2 Glauert, L. (1910). "The Mammoth Cave". Records of the Western Australian Museum. 1. Western Australian Museum: 11–36.
  7. 1 2 3 4 Prideaux, G.J. (2004). Systematics and evolution of the sthenurine kangaroo. University of California Press. ISBN   0-520-09845-5.
  8. 1 2 3 Mitchell, D.R.; Evans, A.R. (11 September 2019). "The anatomy of a crushing bite: The specialised cranial mechanics of a giant extinct kangaroo". PLOS ONE. 14 (9): e0221287. Bibcode:2019PLoSO..1421287M. doi: 10.1371/journal.pone.0221287 . PMC   6738596 . PMID   31509570.
  9. Lyons, Suzannah (12 September 2019). "A jaw made to gnaw: Ancient kangaroos had strong skulls and a serious bite". ABC News.
  10. Gillespie, Richard; Camens, Aaron B.; Worthy, Trevor H.; Rawlence, Nicolas J.; Reid, Craig; Bertuch, Fiona; Levchenko, Vladimir; Cooper, Alan (2012-03-22). "Man and megafauna in Tasmania: closing the gap". Quaternary Science Reviews. 37: 38–47. Bibcode:2012QSRv...37...38G. doi:10.1016/j.quascirev.2012.01.013. hdl: 1885/66219 . S2CID   128951708.
  11. Cosgrove, Richard; Field, Judith; Garvey, Jillian; Brenner-Coltrain, Joan; Goede, Albert; Charles, Bethan; Wroe, Steve; Pike-Tay, Anne; Grün, Rainer (2010-10-01). "Overdone overkill – the archaeological perspective on Tasmanian megafaunal extinctions". Journal of Archaeological Science. 37 (10): 2486–2503. Bibcode:2010JArSc..37.2486C. doi:10.1016/j.jas.2010.05.009. hdl: 1885/37347 . S2CID   128705290.
  12. Webb, Steve (2008). "Megafauna demography and late Quaternary climatic change in Australia: A predisposition to extinction". Boreas. 37 (3): 329–345. Bibcode:2008Borea..37..329W. doi:10.1111/j.1502-3885.2008.00026.x. S2CID   19561004.