Diprotodon

Kingdom: Animalia

Phylum: Chordata

Class: Mammalia 

Order: Diprotodontia

Family: Diprotodontidae

Genus: Diprotodon

Species: D. optatum

Diprotodon, meaning "two forward teeth" is the largest known marsupial ever to have lived. Along with many other members of a group of unusual species collectively called the Australian megafauna, it existed from approximately 1.6 million years ago until extinction some 46,000 years ago.

The closest surviving relatives of Diprotodon are the wobats and the  koala. It is suggested that diprotodonts may have been an inspiration for the legends of the bunyip as some Aboriginal tribes identify identify Diprotodon bones as those of bunyips.

Description

Diprotodon superficially resembled a rhinoceros without a horn. Its feet turned inwards like a wombat's giving it a pigeon-toed appearance it had strong claws on the front feet and its pouch opening faced backward. Footprints of its feet have been found showing a covering of hair which indicates it had similar to a modern wombat. Until recently it was unknown how many species of Diprotodon had existed. Eight species are described although many researchers believed these actually represented only three at most while some estimated there could be around twenty in total.

Up to 3.8 , long (head tail) and 1.7 m at the shoulder.

Habitat

Diprotodon is known from many sites across Australia, including the Darling Downs in southeastern Queensland; Wellington Caves, Tambar Springs Cuddie Springs in New South Wales; Bacchus Marsh in Victria,; Diprotodon is not known from New Guinea, southwestern Western Australia, the Northern Territory oor Tasmania. Diprotodon preferred semi-arid plains, savannahs and open woodlands,and is generally absent from hilly, forested coastal regions. Diprotodon is known from some coastal localities, including Naracoorte Caves and Kangaroo Island in South Australia. However, these areas may have been  further from the coast in the Pleistocene when sea levels were lower.

Australian Pleistocene habitats changed over time in response to the changing climate. Dry, windy conditions alternatated with more equable conditions throughout this period and sea levels were generally much lower than today as ice was locked in polar regions. Extended droughts would have made much of inland Australia uninhabitable; hundreds of individuals have been found at the center of Lake Calabonna in northern South Australi, trapped in the mud as the lake bed dried  out. On the Darling Downs in Queensland, one study of Diprotodon habitat has found that areas once covered in woodlands, vine thickets and scrublands gave way to grasslands as the climate became drier.

Evolution

It is unlikely that Diprotodon moved in large herds, as sometimes depicted. Marsupials are not known to form large groups. The large numbers of individuals found at Lake Callabonna were probably smaller family groups drawn en masse to the drying waterhole. Diprotodontids first appear in the Oligocene, about 25 million years ago. These early diprotodontids were probably descended from late Oligocene to early Miocene to early Miocene wynyardiids and were about the size of sheep.

The subfamily Diprotodontinae, including Diprotodon optatum, are a Pliocene-Pleistocene group.  Diprotodon may have evolved from the Pliocene diprotodontine Euryzygoma during the late Pliocene. A recent study based on dentition has found that there is just a single variable species of Diprotodon, Diprotodon optatum.

Diet

Diprotodon was probably a browser, feeding on shrubs and forbs. One skeleton from Lake Callabonna had the remains of saltbush in its abdominal region. Diprotodon may have eaten as much as 100 to 150 kilograms of vegetation daily. Its chisel-like incisors may have been used to root out vegetation.

Behavior

In diprotodon, male was considerably larger than the females. There was a high degree of morphological difference between the sexes. In living sexually dimorphic mammals, breeding is usually polygynous i. e. males mate with multiple females over the breeding season. Diprotodon may also have used such a breeding strategy. 

There is some evidence of either predation or scavenging of diprotodon by the Pleistocene marsupial lions.

EXTINCTION

Most modern researchers including argue that diprotodonts, along with a wide range of other Australian megafauna, became extinct shortly after humans arrval in Australia about 50,000 years ago.
The recent ice ages produced no significant glaciation in the mainland Australia but long periods of cold and very dry weather. This dry weather during the last ice age may have killed off all the large diprodonts. But this cannot be the main cause because all the megafauna of Australia died in that same time period. Climate change apparently peaked 25,000 years after the extinctions.
May be the human arrival is the main reason of the extinction of the megafauna in Australia  This species died out just after the arrival of the Human. Diprotodon were herbivorous animals so they lived around the grassland or vegetation. Human also lived in the same habitat. Now Diprotodon drew the carnivores to this habitat which hunted the humans too. To reduce these, human killed diprotodons which also reduced the arrival of the carnivores. The human may also killed them for meat.