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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.<ref name="Prideaux2004" /> 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]]''.<ref name="Mitchell2019" />
A set of powerful molars are located close to the hinge of jaw, similar to but further back than a koala, improving the mechanical advantage and reducing the hazard of dislocation while feeding.<ref name="Mitchell2019">{{cite journal |last1=Mitchell |first1=D.R. |last2=Evans |first2=A.R. |title=The anatomy of a crushing bite: The specialised cranial mechanics of a giant extinct kangaroo |journal=PLOS ONE |date=11 September 2019 |volume=14 |issue=9 |pages=e0221287 |doi=10.1371/journal.pone.0221287}}</ref>
Modelling of the bite force and the skulls resistance to torsional forces
The diamond-like shape of the forehead and reinforced cheek bones could distribute the forces applied by large muscles to the rear molars at one side of the jaw, strongly suggesting that browsing 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.<ref name="ABC2019">{{cite news |last1=Lyons |first1=Suzannah |title=A jaw made to gnaw: Ancient kangaroos had strong skulls and a serious bite |url=https://www.abc.net.au/news/science/2019-09-12/giant-sthenurine-short-faced-kangaroos-skulls/11499950 |work=ABC News |date=12 September 2019 |language=en-AU}}</ref>
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Revision as of 05:00, 19 September 2019
Simosthenurus occidentalis | |
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Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Mammalia |
Infraclass: | Marsupialia |
Order: | Diprotodontia |
Family: | Macropodidae |
Genus: | †Simosthenurus |
Species: | †S. occidentalis
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Binomial name | |
†Simosthenurus occidentalis |
Simosthenurus occidentalis is a species of sthenurine marsupial that existed in Australia during the Pliocene, becoming extinct in the Pleistocene epoch around 42 000 years ago. A large herbivorous biped, it is comparable in form to the modern macropods, although considerably larger, and is referred to as a short-faced kangaroo.
Taxonomy
The type specimen was collected by E. A. Le Souef and noted in a report to the Caves Board, then revised and published by Ludwig Glauert as Sthenurus occidentalis in 1910. This holotype is fossil material preserving the left and right dentary of an adult found at Mammoth Cave in Southwest Australia.[1] The specific epithet occidentalis, meaning "of the west", refers to the discovery of this species in Western Australia.[2]
Description
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.[2] 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.[3]
A set of powerful molars are located close to the hinge of jaw, similar to but further back than a koala, improving the mechanical advantage and reducing the hazard of dislocation while feeding.[3] Modelling of the bite force and the skulls resistance to torsional forces suggests that the species was able to consume material tougher than leaves, bark and branches that could be torn with the claws of the forelimbs. The diamond-like shape of the forehead and reinforced cheek bones could distribute the forces applied by large muscles to the rear molars at one side of the jaw, strongly suggesting that browsing 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.[4]
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.[3] 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.[2]
Their distribution in the Pleistocene is dated to late-middle to late deposits.[2]
References
- ^ a b Glauert, L. (1910). "The Mammoth Cave". Records of the Western Australian Museum. 1. Western Australian Museum,: 11–36.
{{cite journal}}
: CS1 maint: extra punctuation (link) - ^ a b c d Prideaux, G.J. (2004). Systematics and evolution of the sthenurine kangaroo. University of California Press. ISBN 0-520-09845-5.
- ^ a b c 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. doi:10.1371/journal.pone.0221287.
{{cite journal}}
: CS1 maint: unflagged free DOI (link) - ^ Lyons, Suzannah (12 September 2019). "A jaw made to gnaw: Ancient kangaroos had strong skulls and a serious bite". ABC News.