Thylacoleo

a.k.a. ‬Marsupial Lion‭.

Name: Thylacoleo ‭(‬Pouch lion‭)‬.

Phonetic: Fy-lak-o-lee-oh.

Named By: Richard Owen‭ ‬-‭ ‬1859.‭

Classification: Chordata,‭ ‬Mammalia,‭ ‬Marsupialia,‭ ‬Diprotodontia,‭ ‬Thylacoleonidae.

Species: T.‭ ‬carnifex‭ (‬type‭)‬,‭ ‬T.‭ ‬crassidentatus,‭ ‬T.‭ ‬hilli.

Diet: Carnivore.

Size: Largest species (T. carnifex) up to 75 centimetres high at the shoulder. Smallest species (T. hilli) roughly half this size..‭ ‬Average weight was between‭ ‬100‭ ‬and‭ ‬130‭ ‬kilograms,‭ ‬but larger individuals could approach‭ ‬160‭ ‬kilograms.

Known locations: Australia.

Time period: Zanclean of the Pliocene through to Ionian of the Pleistocene.‭ *‬note‭ ‬-‭ ‬different species appear at different times of the fossil record.

Fossil representation: Many specimens,‭ ‬some of which are almost complete allowing for accurate reconstruction.

Although often dubbed the‭ ‘‬Marsupial lion‭’‬,‭ ‬Thylacoleo was not related to existing lions today which are members of the Pantherinae.‭ ‬On top of this,‭ ‬todays big cats like lions are what are known as placental mammals,‭ ‬which means that young develop while attached to a placenta inside of the mother‭’‬s body.‭ ‬Thylacoleo however was a marsupial which means that young were passed into an external pouch at a very early stage of their development.‭ ‬Development would continue inside the much until the young were ready to walk about for themselves.‭ ‬Young would have stayed with the mother until they were capable of hunting for themselves,‭ ‬although they may have eventually been chased off by the mother as she became reproductively receptive again.

The instantly recognisable features of Thylacoleo are the hyper specialised teeth.‭ ‬The upper and lower jaw incisors‭ (‬front teeth‭) ‬are greatly enlarged in a manner reminiscent of rodents.‭ ‬The carnassial premolars are also shaped like blades that provided a shearing motion.‭ ‬Some interpretations of Thylacoleo saw it using these teeth for eating nuts and fruit,‭ ‬however later research found wear on them to match a carnivorous diet.‭ ‬It is now considered most probable that Thylacoleo used its immensely powerful jaw muscles to drive these teeth through critical locations such as the neck and spine.‭ ‬Analysis of the structure of the jaws and the muscle attachment indicates that Thylacoleo had a bite comparable to a lion that was two and a half times larger than the Thylacoleo individual in question‭ (‬e.g.‭ ‬a one hundred kilogram Thylacoleo would have a bite equivalent to a two hundred and fifty kilogram lion‭)‬.

Thylacoleo also possessed a number of other adaptations that could have helped in its hunting.‭ ‬The caudal vertebrae of the tail had well developed chevrons for strong muscle attachment that would have combined with the overall robustness of the tail so that it could be used as a support.‭ ‬Other Australian marsupials such as the kangaroo can today be observed balancing upon their tails as they kick at other kangaroos during combat.‭ ‬Thylacoleo might not have been able to support its entire weight upon its tail,‭ ‬but the tail would still have formed an effective support that helped to prevent Thylacoleo from being tipped backwards when wrestling against prey.‭ ‬It may even have been used as support during intraspecific combat between two individuals.

The forelimbs of Thylacoleo were also well developed with killing adaptations.‭ ‬One thing that Thylacoleo had that made it unusual amongst marsupials was retractable claws.‭ ‬Because the claws were retracted when not being used they could be kept free from contact with the ground so that they did not become blunt.‭ ‬Thylacoleo also had a partially opposable first‭ ‘‬thumb‭’‬ digit that could have been used for extra grip on prey animals.

However the opposable thumb and sharp claws were not necessarily just for killing as they were also capable of gripping trees for climbing.‭ ‬Further support for Thylacoleo’s climbing ability comes from the rear feet where the first toe was reduced but displayed a rough pad.‭ ‬This is also seem in possums and provides a textured surface that for extra grip on trees and branches as the claws of the fore paws dig in to the bark as they pull themselves up.‭ ‬Tree climbing is known in some big cats like leopards where they drag dead prey into trees so that it cannot be stolen by other predators.‭ ‬This could also be true for Thylacoleo as even though it was not the only powerful predator‭ ‬in pleistocene Australia,‭ ‬it was one of the few large predators that had the potential to climb.

With these adaptations Thylacoleo is thought to have hunted other large marsupial mammals such as Palorchestes and Procoptodon.‭ ‬Thylacoleo would have also needed every one of these strengths to survive in environments that contained other large predators such as the terrestrial crocodile Quinkana,‭ ‬and the goanna Varanus priscus.

Further reading

- On the fossil mammals of Australia. Part II. Description of a mutilated skull of the large marsupial carnivore (Thylacoleo carnifex Owen), from a calcareous conglomerate stratum, eighty miles S. W. of Melbourne, Victoria. - Philosophical Transactions of the Royal Society 149, 309-322. - Richard Owen - 1859.

- On the fossil mammals of Australia. Part IV. Dentition and mandible of Thylacoleo carnifex, with remarks on arguments for its herbivory. - Philosophical Transactions of the Royal Society 161, 213-266. - Richard Owen - 1871.

- The skull of Thylacoleo carnifex. - Memoirs of the Queensland Museum 13, 125-140. - J. T. Woods - 1956.

- A new species of Thylacoleo (Marsupialia, Thylacoleonidae), with notes on the occurrence and distribution of Thylacoleonidae in South Australia. - Records of the South Australian Museum 17, 277-283. - N. Pledge - 1977.

- On the manus and pes of Thylacoleo carnifex Owen (Marsupialia). - Transactions of the Royal Society of South Australia 101,139-146. - R. T. Wells & B. Nichol - 1977.

- Thylacoleo carnifex Owen (Thylacoleonidae): marsupial carnivore? pp. 573-585 in Archer, M. (ed) Carnivorous Marsupials, Vol. 2. Royal Zoological Society of New South Wales, Mosman - R. Wells, D. R. Horton & P. Rogers - 1982.

- The discovery and interpretation of Thylacoleo carnifex (Thylacoleonidae, Marsupialia). pp. 537-551 in Archer, M. (ed) Carnivorous Marsupials, Vol. 2. Royal Zoological Society of New South Wales, Mosman. - M. E. Finch - 1982.

- An odontometric study of the species of Thylacoleo (Thylacoleonidae, Marsupialia). pp. 553-572 in Archer, M. (ed) Carnivorous Marsupials, Vol. 2. Royal Zoological Society of New South Wales, Mosman. - M. E. Finch & L. Freedman - 1982.

- Estimating the weight of the Pleistocene marsupial lion, Thylacoleo carnifex (Thylacoleonidae : Marsupialia): implications for the ecomorphology of a marsupial super-predator and hypotheses of impoverishment of Australian marsupial carnivore faunas - Australian Journal of Zoology 47 (5): 489–498. - S. Wroe, T. J. Myers, R. T. Wells & A. Gillespie - 1999.

- An alternative method for predicting body mass: the case of the Pleistocene marsupial lion. - Paleobiology 29, 404-412. - S. Wroe, T. J. Myers, F. Seebacher, B. Kear, A. Gillespie, M. Crowther & S. Salisbury - 2003.

- Pedal morphology of the marsupial lion Thylacoleo carnifex (Diprotodontia: Thylacoleonidae) from the Pleistocene of Australia. - Journal of Vertebrate Paleontology, 29:4, 1335-1340. - Roderick T. Wells, Peter F. Murray & Steven J. Bourne - 2009.

-An ancient rock painting of a marsupial lion, Thylacoleo carnifex, from the Kimberley, Western Australia. - Antiquity Volume 083 Issue 319 - Kim Akerman & Tim Willing - 2009.

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