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What is a Thylacine?

The Thylacine (Thylacinus cynocephalus: dog-headed pouched-dog) is a large carnivorous marsupial now believed to be extinct. It was the only member of the family Thylacinidae to survive into modern times. It is also known as the Tasmanian Tiger or Tasmanian Wolf.

What did it look like?

The Thylacine was sandy yellowish-brown to grey in colour and had 15 to 20 distinct dark stripes across the back from shoulders to tail. Although the large head was dog- or wolf-like, the tail was stiff and the legs were relatively short.

The female Thylacine had a back-opening pouch. The litter size was up to four and the young were dependent on the mother until at least half-grown. Interestingly, males also had a back-opening, partial pouch.

What did it eat?

The Thylacine was mainly nocturnal or semi-nocturnal but was also out during the day. The animal moved at a slow pace, generally stiff in its movements. The Thylacine hunted singly or in pairs and mainly at night. Thylacines preferred kangaroos and other marsupials, small rodents and birds.

Where did it live?

At one time the Thylacine was widespread over continental Australia, extending north to New Guinea and south to Tasmania.

Why did it become extinct?

Its decline and extinction in Tasmania was probably hastened by the introduction of dogs, but appears mainly due to direct human persecution as an alleged pest. The last known recorded sighting of the Thylacine in captivity was filmed at the Beaumaris Zoo in Hobart, Tasmania, 1936.

Conclusion

The Thylacine was a special animal from Australia. It looked like a dog, but it had stripes and a pouch like a kangaroo. It hunted small animals at night and lived in many parts of Australia and Tasmania. Sadly, the Thylacine became extinct because people hunted it and dogs were brought into its home. The last known Thylacine died in a zoo in 1936. Today, we remember the Thylacine as an important part of Australia’s history.

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What is a thylacine? Why did it become extinct?

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Be Smart | The Strange Evolutionary Story of the Thylacine | Season 6 | Episode 15

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Here’s the science of convergent evolution!

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The Riversleigh Rainforest Koala, called Nimiokoala greystanesi, is an extinct type of koala that lived in Australia about 20 million years ago. It was found at the Riversleigh Fossil Site in Queensland. This ancient koala was much smaller than today’s koalas and had a longer snout. Even though it looked different, it was still a tree-dwelling marsupial and part of the koala family.

Appearance and Diet

Nimiokoala was about 25 to 30 centimeters long, which is about one-third the size of a modern koala. It had sharp teeth that helped it chew leaves, and it probably lived in trees. Scientists aren’t sure exactly what kinds of leaves it ate, but it likely ate many types, not just eucalyptus like today’s koalas. Its longer snout and special teeth made it different from modern koalas.

Habitat and Fossil Finds

This koala lived in a rainforest area with streams and open spaces. Over time, Australia’s rainforests began to shrink and became drier. Since Nimiokoala lived in a rainforest environment, the loss of its habitat may have made it harder to survive. Fossils were found in the limestone rocks at Riversleigh. These include a skull, lower jaw bones, and teeth. Fossils of koalas are rare, so finding a well-preserved skull is very important. The fossils are now kept at the Queensland Museum.

Conclusion

The Riversleigh Rainforest Koala helps us understand how today’s koalas came to be. Even though it is extinct, it tells an important story about life in Australia millions of years ago. With each fossil found, scientists learn more about how animals changed and adapted to their environments over time. In summary, Nimiokoala greystanesi is an important piece of Australia’s natural history and helps us see how ancient animals shaped the wildlife we know today.

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Riversleigh Rainforest Koala, Nimiokoala greystanesi was a small koala from the early Miocene of northern Australia. It had a longer snout than the living koala but was only about a third of its size. is represented by a well preserved skull, a significant discovery since koalas are rare in the fossil record. Nimiokoala would have fed on the leaves of forest trees although it is not known whether it specialized on the leaves of eucalypts, as the living koala does.

Identification

Koalas are stocky, arboreal marsupials with long arms, short legs with syndactylous (joined) second and third toes, and a backwardly-facing pouch (an inheritance from burrowing ancestors). They have two forwardly directed lower incisors, and are thus included in the order Diprotodontia. The molar teeth of koalas are complex and selenodont, with W-shaped lophs or blades on each tooth that cut leafy vegetation like a pair of pinking shears. Fossil koalas are distinguished mainly by differences in cusps and crests on molars. All koalas lack first and second premolar teeth although they have retained a third premolar. They also have canine teeth on the upper jaw although the lower jaw has lost its canine.

Nimiokoala is exceptionally rare in being represented by a well-preserved skull with dentition. Lower jaws and isolated teeth have also been found, and the entire dentition has now been recovered. Nimiokoala had a longer snout than the living koala, Phascolarctos cinereus, which has an exceptionally short face. Nimiokoala is distinguished from other koalas by the following 'short list' of dental features: the paraconule and metaconule on M1-4/ are well-developed and crescentic; the neometaconule is double-cusped on more posterior molars; and the M4/ has comparatively reduced metacone and metaconule, with a more rounded posterior margin (see Black and Archer 1997 for further description).

Habitat

Riversleigh from the early to middle Miocene was mainly forested, with more open areas near the forest edges and freshwater streams or lakes in a karst (limestone) environment.

Distribution

Nimiokoala greystanesi is known only from the Riversleigh World Heritage Fossil Site in northwestern Queensland.

Related to: Nimiokoala is most closely related to a possible second species of Nimiokoala from the late Oligocene Frome Basin, South Australia (still undescribed). Nimiokoala is also closely related to the fossil koalas Litokoala and to the genus Phascolarctos, to which the living koala Phascolarctos cinereus belongs.

Feeding and diet

The diet of Nimiokoala is unknown, other than it browsed on the leaves of forest trees. Perhaps, like the living koala, it ate the leaves of gum trees (relatively rare in Miocene forests). Alternatively, as an early member of the koala family and therefore less specialised, Nimiokoala may have fed on a variety of leaves.

Life history cycle

As a marsupial, Nimiokoala would have had tiny young at birth that continued development in a pouch until ready for weaning. It probably had a backward-opening pouch, as in living koalas and wombats (an unlikely development for an arboreal animal, retained from the koala's burrowing ancestors).

The living koala has a very specialized lifestyle and is restricted to feeding on the leaves of eucalypts. Nimiokoala was almost certainly arboreal, but its diet is unknown other than the leaves of trees. Nimiokoala lived alongside at least one other species of koala, Litokoala kutjamarpensis, during the early Miocene. Since we know little else about Nimiokoala and have not yet recovered skeletal material, we can make few other assumptions about its life history.

Fossils description

Nimiokoala greystanesi is known from a partial skull with teeth (I1/ to M2/), several lower jaws and a number of isolated teeth. The entire dentition has now been recovered. Nimiokoala was found at the Riversleigh World Heritage Fossil Site (System B; Neville's Garden). Material is held by the Queensland Museum, Brisbane.

Evolutionary relationships

Koalas are most closely related to wombats, having shared a common ancestor in the Oligocene or earlier. Both are members of the suborder Vombatiformes (order Diprotodontia). Diprotodontoids (large, herbivorous marsupials whose best known member is the massive Diprotodon) are also included in Vombatiformes. Most scientists believe that vombatiforms are at the base of the diprotodontian radiation (vombatiforms, possums and kangaroos). One study of marsupial relationships based on molecular evidence places Vombatiformes at the base of the Diprotodontia, 'up the tree' from microbiotheres (South American marsupials closely related to Australian marsupials) and other non-diprotodontian, generally carnivorous marsupials (Kirsch et al. 1997).

The first arboreal koalas probably evolved from a terrestrial wombat-like ancestor, perhaps to take advantage of a food resource not being utilized by others. Koalas were once much more widespread across Australia: fossil koala species are known from southern, western and central Australia when rainforest was more widespread across these parts of the continent. There are now six genera and at least 18 species of fossil koalas (some species are not yet described). All are from either South Australia or Queensland (Riversleigh).

The late Oligocene fossil koala Madokoala and the late Oligocene-early Miocene Perikoala are closer to the stem of the koala family tree than is Nimiokoala. Nimiokoala is presently considered the primitive sister taxon to a group that includes the fossil koalas Litokoala and Phascolarctos (the genus to which the living koala Phascolarctos cinereus belongs). The genus Phascolarctos first appears in the late Miocene/early Pliocene, with at least two other species known (the huge P. yorkensisfrom the late Miocene to Pleistocene of South Australia and New South Wales); and P. maris and/or P. stirtoni from the early Pliocene of South Australia.

References

Black, K. and Archer, M. 1997a. Nimiokoala gen. nov. (Marsupialia, Phascolarctidae) from Riversleigh, northwestern Queensland, with a revision of Litokoala. Memoirs of the Queensland Museum 41, 209-228.

Louys, J., Black, K., Archer, M., Hand, S. J. and Godthelp, H. 2007. Descriptions of koala fossils from the Miocene of Riversleigh, northwestern Queensland and implications for Litokoala (Marsupialia, Phascolarctidae). Alcheringa 31, 99-110.

Stirton, R. 1957b. A new koala from the Pliocene Palankarinna fauna of South Australia. Records of the South Australian Museum 13, 71-81.

Stirton, R. A., Tedford, R. H. and Woodburne, M. O. 1967. A new Tertiary formation and fauna from the Tirari Desert, South Australia. Records of the South Australian Museum 15, 427-461.

Woodburne, M. O., Tedford, R. H., Archer, M. and Pledge, N. S. 1987a. Madokoala, a new genus and two species of Miocene koalas (Marsupialia: Phascolarctidae) from South Australia, and a new species of Perikoala. Pp. 293-17 in Archer, M. (ed) Possums and Opossums: Studies in Evolution. Surrey Beatty & Sons, Chipping Norton.

Further reading

Archer, M., Hand, S. J. and Godthelp, H. 1994. Riversleigh: The Story of Animals in Ancient Rainforests of Inland Australia. Reed Books, Chatswood.

Jackson, S, 2007. Koala: Origins of an Icon. Allen and Unwin, Sydney.

Long, J. A. et al. 2002. Prehistoric Mammals of Australia and New Guinea: One Hundred Million Years of Evolution. Johns Hopkins University Press, Baltimore, 240 pp.

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Nimiokoala greystanesi was a small koala from the early Miocene of northern Australia. It had a longer snout than the living koala but was only about a third of its size. Nimiokoala is represented by a well preserved skull, a significant discovery since koalas are rare in the fossil record.