The Marsupial Lion (Thylacoleo carnifex)

Classification

Phylum： Chordata

Class： Mammalia

Sub-class： Marsupialia

Order： Diprotodontia

Super family： Vombatomorphia

Family： Thylacoleonidae

Genus： Thylacoleo

Species： carnifex

Common names： Pleistocene Marsupial Lion,

　Marsupial Leopard

Probable diet

Historically, the Thylacoleo carnifex diet has been debated but there is evidence that they could kill the heaviest megafauna the Diprotodon, which is estimated to weigh one tonne. Other prey would be the giant kangaroos such as Sthenurus, and phascolonus. Thus, the Thylacoleo carnifex was thought to have probably been a ‘big-game’specialist. It most likely ambushed it prey because it had a large powerful carnivore, which lacked the skeleton structure to sustain long chases. The skeleton is also developed to leap and has possum like paws. This evidence would imply that they were climbers but this is debatable. It has competed with the large marsupials from the giant goanna Megalania prisca and the Wonambi.

Probable normal habitat

The habitat of the Thylacoleo carnifex would include forests, woodlands, shubland and near water holes. It would not survive in very open land due to its lack of speed. The T. carnifex would need to ambush or stalk their prey at close range to capture them.

Period of existence in Australian

The Thylacleo carnifex is considered to have lived during the Pliocene and the Pleistone geologic period. There is evidence of them from 40 thousand to 1.6 million years ago.

The palaentologic evidence

In fact, there was early miss classification of the Thylacoleo carnifex. Tyndale-Biscoe believed that the T. carnifex was related to Phalangeroidae (possums) which would place them in the Phalan-gerida sub family. He has pointed out that the T.carnifex paws are possum like, which suggests that it is a tree climbing creature similar to Panthera leo.Finch has stated:“…was large and heavy and did not have the well developed subscapularis minor muscles needed to resist the anterior pull on the scapula during climbing” (1988, p270-271).

The dental morphology gives significant clues to the diet of the T. carnifex. The T. carnifex has un-usual teeth for a predator since it is from the herbivorous Vombatomorphia. The canine teeth are used by cats and wolves to kill its prey yet T.carnifex has quite small canines. It has been suggested that the front incisors were used because of their slight curve and strong shape. The third premolars were large and used against each other to slice meat and break bones.

The diet of the T.carnifex is thought to be similar to large herbivores such as Diprotodon, Sthenurus and Phascolonus. Milewka has argued that a full size Diprotodon or Sthenurus could not have been killed by this predator. He continues by saying that Thylacoleo only preyed on the pouch young of large marsupials. On the other hand, the bones of the marsupial lion were associated with the bones of Diprotodon and Sthenurus, suggesting that they could kill these large prey. Thylacinus cyno-cephalus existed at the same time as the T.carnifex. Their dimension is quite similar but to avoid direct competition the T.carnifex evolved to hunt larger prey.

The tarsals and metapodial mechanics of the T.carnifex show that they are not really as develoved as other predators such as cats. This evidence has suggested that their running speed is limited and probably they are not able to reach the speed that a kangaroo can (Szalay, 1994). This would indi-cate that they ambushed their prey at close range where they could use their powerful paws and jaw. As for their limbs, scapular and pelvis structures it is thought that the animal was a capable at leap-ing. Whether it was a agile climber is unsure, but considering the size and weight of the animal its less likely than the other smaller thylacoleonidae.

Proposed explanation for extinction of the megafauna

The issue of extinction of the megafauna has been debated for the last 30 years, which continues today. There are two main theories about the cause of extinction of the megafauna―the impact of humans in Australia and an arid climate change after the last ice age. So did human beings wipe out the megafauna by direct predation or habitat changes? Did the climate change to arid environment detrimentally affect on the megafauna? Was it a combination of these two events?

The environment of historic Australia needs to be explored to understand both theories. Over the last 140 thousand years, there have been several ice ages. The two largest were the Last Ice Age (20 thousand years ago) and the Third Ice Age (140 thousand years ago). In these periods, the sea level dropped down 110 meters, which greatly increased the land mass of Australia and open land bridges from New Guinea and the Asian continent (see figure 2 and 3). These land bridges allowed people to cross straits and move in to Australia. There is no evidence that humans migrated in the Third Ice

Age. The oldest known evidence of human is 62000 years ago (Tyndale-Biscoe 2005). This sug-gests that humans crossed between 75 and 60 thousand years ago when the sea level was 50 meters below present level. Figure2: The Sea Level in the last 140 thousand years

(Tyndale-Biscoe 2005)

Figure3: The Australian land mass 20 thousand years ago

(Tyndale-Biscoe 2005)

The extinction of the largest megafauna including diprotodon and the largest macropods is thought to be around 40000 years ago. Roberts et al (2001) used new dating techniques on 23 extinct fossils. They ranged from 80 to 37 thousand years old. Roberts concluded that most species of megafauna are extincted by 44 thousand years ago. This is still challenged by many, a Diprotodon bone from Lake Menindee, NSW was C14 dated at 11 thousand years ago.

The climate change theory is strengthened by the agile wallaby extinction on Aru Island. The island was isolated from the main land after the last Ice Age. There was no human inhabitant on the island. The change in vegetation was influential fact of the extinction of the species. This is because of the dries and cools climate has made plants become less nutritious.

Although the megafauna are hunted to extinction with in a short time in North America, and Horse and mammoths only lasted one thousand years, it did not happened in Australia. Also, humans and the megafauna coexisted for at least 20 thousand years. In Australia, the humans did not have the advanced tools to kill the largest animals.

The development of technology around 7 to 5 thousand years ago brought finely worked flake and wooden handles tools (Mulvaney et al 1999). At Lake Menindee, young beds contain more smaller advanced points and blades and there were a lack of megafauna except Thylacine and Sarcophilus harrisii. This suggests that between 10 and 4 thousand years ago the Aborigines changed their hunt-ing systems, from heavy course stone to fine well made microliths better for use on spears and bet-ter for hunting faster and smaller animals. Aborigines hunted in small groups that could not eat a large megafauna before it went rotten. This would suggest that the aboriginal hunted mainly smaller megafauna and juvenile of the larger species.

Moreover, the Aborigines were hunting the megafauna, to what extent is uncertain. It is unlikely that they had sufficient tools or the numbers to hunt the megafauna to extinction. The Aborigines has another important impact on the megafauna, they periodically set fire to the bush. This cleared out the under growth and allowed generation. This attracts kangaroos and wallabies and allows eas-ier hunting and travel. This is thought to have detrimental effect on the browsers such as Sthenurus and other short faced kangaroos (Augee et al 2000).

The vegetation also changed with the introduction of periodic fires, the fire resistant plants gained an advantage and fire resistant species of Eucalyptus become prominent. The demise in the large herbivorous megafauna, would lead to starvation of the large predators like the T.carnifex.

Therefore, the most probable theory of the extinction of the megafauna is a combination of mainly human factors and the increasingly arid environment. The megafauna that survived after the Last Ice Age were most likely wiped out by the increasingly arid conditions.

Bibliography

Augee, M, Fox, M 2000 Biology of Australia and New Zealand, Pearson Education Australia, Syd-ney

Finch, M, Freedman, L 1988 ‘Functional-morphology of the limbs of Thylacoleo-Carnifex Owen’ Australian Journal of Zoology vol. 36, no.3<http://www.publish.csiro.au/paper/ZO9880251.htm>( This website was a online link to the Australian Journal of Zoology so it is reliable)

Finch, M, Freedman, L 1986 ‘Functional-morphology of the vertebral column of Thylacoleo-Carnifex Owen’ Australian Journal of Zoology vol. 34, no.1 <http://www.publish.csiro.au/paper/ZO9860001.htm>

Finch, M 1982 Thylaceleo carnifex owen, An Australian fossil phalangeridmarsupial: taxonomy, function morphology, feeding and locamative University of Western Austra-lia, Perth

Milewka, A 2003 Marsupial Lion or pouch-raiding possum? Australasian Science, no. 24, pp 14 - 17

Mulvaney, J, Kamminga, J 1999 Prehistory of Australia Allen and Unwin, Sydney

Roberts, R, Flannery, T, Ayliffe, L, Yoshida, H, Olley, J, Prideaux, G, Laslett, G, Baynes, A, Sith, M, Jones, R, Smith, B 2001 New ages for the Australian mega fauna: continent-wide extinction about 46,000 years ago Science vol. 292, pp 1888-92

Szalay, F 1994 Evolutionary history of the marsupials and an analysis of osteological characters Cambridge University Press, Cambridge

Tyndale-Biscoe, H 2005 Life of Marsupials CISRO Publishing, Collingwood VIC