Diprotodontia
Diprotodontia Ma Late Oligocene – Recent
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Clockwise from upper left: female koala (Phascolarctos cinereus), mahogany glider (Petaurus gracilis), young eastern grey kangaroo (Macropus giganteus) and Sulawesi bear cuscus (Ailurops ursinus) | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Mammalia |
Infraclass: | Marsupialia |
Clade: | Eomarsupialia
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Order: | Diprotodontia Owen, 1866 |
Suborders | |
Diprotodontia (
Characteristics
Living diprotodonts are almost all
Diprotodonts are restricted to Australasia. The earliest known fossils date to the late Oligocene, but their genesis certainly lies earlier than this, as large gaps occur in Australia's fossil record, with virtually no fossil record at all in geologically active New Guinea. The great diversity of known Oligocene diprotodonts suggests the order began to diverge well beforehand.[citation needed]
Many of the largest and least athletic diprotodonts (along with a wide range of other Australian megafauna) became extinct when humans first arrived in Australia about 50,000 years ago. Their extinction possibly occurred as a direct result of hunting, but was more probably a result of widespread habitat changes brought about by human activities—notably the use of fire.[citation needed]
Two key anatomical features, in combination, identify Diprotodontia. Members of the order are, first, "diprotodont" (meaning "two front teeth"): they have a pair of large, procumbent incisors on the lower jaw, a common feature of many early groups of mammals and mammaliforms. The diprotodont jaw is short, usually with three pairs of upper incisors (wombats, like rodents have only one pair), and no lower canines. The second trait distinguishing diprotodonts is "syndactyly", a fusing of the second and third digits of the foot up to the base of the claws, which leaves the claws themselves separate.[3] Digit five is usually absent, and digit four is often greatly enlarged.
Syndactyly is not particularly common (though the Australian omnivorous marsupials share it) and is generally posited as an adaptation to assist in climbing. Many modern diprotodonts, however, are strictly terrestrial, and have evolved further adaptations to their feet to better suit this lifestyle. This makes the history of the tree-kangaroos particularly convoluted: it appears that the animals were arboreal at some time in the far distant past, moving afterward to the ground—gaining long kangaroo-like feet in the process — before returning to the trees, where they further developed a shortening and broadening of the hind feet and a novel climbing method.[citation needed]
Fossil record
The earliest known
Classification
Cladogram of Diprotodontia by Upham et al. 2019[5][6] and Álvarez-Carretero et al. 2022[7][8] | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Until recently, only two
Order Diprotodontia
- Suborder Vombatiformes
- Family Vombatidae: wombats(three species)
- Family Phascolarctidae: koala (one species)
- Family †Ilariidae
- Family †Maradidae
- Family †Diprotodontidae: (giant wombats)
- Family †Palorchestidae: (marsupial tapirs)
- Family †Thylacoleonidae: (marsupial lions)[10]
- Family †Wynyardiidae
- Family
- Suborder Phalangeriformes
- Superfamily Phalangeroidea
- Family Phalangeridae: (brushtail possums and cuscuses)
- Family Burramyidae: (pygmy possums)
- Family †sprite possums)
- Superfamily Petauroidea
- Family Tarsipedidae: (honey possum)
- Family Petauridae: (striped possum, Leadbeater's possum, yellow-bellied glider, sugar glider, mahogany glider, squirrel glider)
- Family ring-tailed possumsand allies)
- Family Acrobatidae: (feathertail glider and feather-tailed possum)
- Family
- Superfamily Phalangeroidea
- Suborder Macropodiformes
- Family †Balbaridae: (basal quadrupedal kangaroos)
- Family Macropodidae: (kangaroos, wallabies and allies)
- Family rat-kangaroos)
- Family Hypsiprymnodontidae: (musky rat-kangaroo)
† means extinct family, genus or species