Procoptodon
Procoptodon Temporal range:
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Procoptodon gilli skull. | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Mammalia |
Infraclass: | Marsupialia |
Order: | Diprotodontia |
Family: | Macropodidae |
Subfamily: | †Sthenurinae |
Genus: | †Procoptodon Owen, 1873 |
Type species | |
P. goliah | |
Species[1] | |
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Procoptodon
The genus is derived from
Description
Procoptodon physiology was likely similar to that of the contemporary kangaroos; however, Procoptodon goliah was characterised by its large size. These sthenurines, or short-faced kangaroos, included species that were more than three times the size of the largest kangaroos living today. The largest, P. goliah, was 2.7 m (8 ft 10 in) tall and weighed up to 240 kg (530 lb).[5] These animals lived alongside modern species of kangaroos, but specialised on a diet of leaves from trees and shrubs. Procoptodon were large and short-faced, distinguishable by their flat faces and forward-pointing eyes. On each foot, they had a single large toe or claw, similar in appearance to a horse's hoof. On feet, Procoptodon would have moved quickly through the open forests and plains, where they sought grass and leaves to eat. Both two of their front paws had two extra long fingers with large claws. These long claws may have been used to grab branches, and bring leaves to a distance where the animal could eat them.[6][7]
Distribution and habitat
Procoptodon is mainly known for living in semiarid areas of
Palaeobiology
Mobility
Procoptodon was not able to hop as a mode of transportation, and would have been unable to accelerate sufficiently due to its weight.[9] Broad hips and ankle joints, adapted to resist torsion or twisting, point to an upright posture where weight is supported by one leg at a time. Its broad hips also allowed for another important modification – large buttocks – a feature shared with other walking species.[5]
However, some ambiguity surrounds the possible locomotion of P. goliah. Some research suggests that this species was perhaps the largest hopping mammal to have ever existed.[4] Research suggests that the most optimal weight for a large hopping marsupial is roughly 50–60 kg. Larger animals, especially the massive P. goliah, would be substantially more at risk of tendon breakage while hopping.[4] If P. goliah were to have travelled by hopping, the highest possible balance between size and speed would have been peaked, because its body would have been the largest possible to be carried by this method of locomotion.[10]
A more likely suggestion, based on the apparent anatomy allowed by the bone structure of P. goliah, is that unlike modern kangaroos, which are plantigrade hoppers at high speeds and use their tails in pentapedal locomotion at slower speeds, Procoptodon was an unguligrade biped, walking in a fashion similar to
Fossils of giant short-faced kangaroos have been found at the Naracoorte World Heritage fossil deposits in South Australia, Lake Menindee in New South Wales, the Darling Downs in Queensland, and at many other sites. A full-sized, lifelike replica is on permanent display with other ancient native Australian animals at the Australian Museum.[3]
Diet and molar patterns
These animals lived alongside modern species of kangaroos, but specialised on a diet of leaves from trees and shrubs.
Extinction
The genus was present until at least about 45,000 years ago before going extinct, although some evidence indicates it may have survived to as recently as 18,000 years ago. Its extinction may have been due to climate shifts during the Pleistocene,[3] or to human hunting.[6] Those who support the hypothesis of a human-mediated extinction process cite that the arrival of humans to continental Australia occurred around the same time as the disappearance of this species.[15] More evidence that this extinction was facilitated by human interaction is that the time period in which the extinction occurred was characterised by a relatively stable climate.[15] However, no evidence of predation on or consumption of P. goliah by humans has been found in the fossil record.[15]
New evidence has been found, however, which shows humans arrived 10,000–15,000 years prior to extinction.[16]
Some researchers have speculated that the replacement of nutritious, fire-sensitive plants with less flammable, less nutritious flora brought about by human, fire-based deforestation in Australia played a large role in P. goliah and other
Environmental factors
Kangaroos living in dry, arid environments have been shown to exhibit higher densities of tooth enamel, caused by indirect hydration through consuming herbaceous plants. Lower levels of this enamel in P. goliah teeth found in areas with similar environmental parameters compared to the modern grazing kangaroos suggests that it relied far more heavily on free-standing water sources such as lakes and streams.[6]
Given the larger size of P. goliah and its tendency to favor larger, free-standing water sources, episodic droughts accumulating 55 kya in the southern interior region of Australia would have certainly affected its populations. Yet, records show that such droughts had characterised this region for the previous 7 million years, with P. goliah surviving multiple intensely dry episodes during this period. Any period of significant decreases in rainfall did not occur until 5,000–10,000 years after the approximate extinction of P. goliah 45–50 kya, 20 ky before the last glacial maximum of high aridity. These factors disprove speculations that such droughts could have played a significant role in the extinction of P. goliah.[6]
Some evidence supports both of the claims that the extinction of P. goliah may have been due to
References
- ^ ISBN 9780520916050.
- ^ Haaramo, M. (2004-12-20). "Mikko's Phylogeny Archive: Macropodidae - kenguroos". Archived from the original on 2007-03-31. Retrieved 2007-03-15.
- ^ a b c d e "Procoptodon goliah". Australian Museum. Retrieved 2012-03-22.
- ^ doi:10.1071/ZO05077.
- ^ a b c d Gruber, Karl (15 October 2014). "Giant prehistoric kangaroos walked, not hopped". Australian Geographic. Australian Geographic Society. Retrieved February 22, 2018.
- ^ PMID 19556539.
- ^ a b Field, Judith and Wroe, Stephen. Aridity, faunal adaptations and Australian Late Pleistocene extinctions. World Archaeology. Mar 2012, Vol. 44 Issue 1, p 56–74. 19p.
- ^ Fedorowytsch T.. 2017. Fossil footprints reveal Kangaroo Island's diverse ancient wildlife. ABC Net News. Retrieved on July 24, 2017
- ^ PMID 25333823.
- ^ a b Webb, Steve. Corridors to Extinction and the Australian Megafauna. Burlington: Elsevier Science, 2013. Print.
- ^ Andy Coghlan (Oct 18, 2014). "Extinct giant kangaroos didn't hop, they walked". New Scientist.
- ^ PMID 18086129.
- ISBN 9780909674366. Retrieved February 22, 2018 – via archive.org.
- ^ ISBN 9780643106277. Retrieved 20 October 2014.
- ^ PMID 23650401.
- ^ "New artefacts extend arrival of First Australians to 65,000 years ago". SBS.com.au. SBS. 20 July 2017. Retrieved February 22, 2018.