Download The Marsupial Lion (Thylacoleo carnifex)

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 Phalangerida 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 unusual 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 cynocephalus 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 indicate 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 leaping. 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 suggests 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 hunting systems, from heavy course stone to fine well made microliths better for use on spears and better 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 easier 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, Sydney
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 ThylacoleoCarnifex 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 phalangerid
marsupial: taxonomy, function morphology, feeding and locamative University of Western Australia, 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