What does Doraemon, who has big buck teeth, hide in his pocket?

Australia is a magical land. There are kangaroos, wombats, and even marsupial moles and numbats. So, are there marsupial cats (not Doraemon)? There really is an extinct "marsupial cat" - the marsupial lion (Thylacoleo carnifex). The genus name Thylacoleo means "marsupial lion". As the name suggests, it is the largest known marsupial carnivore and a "competitor" of the marsupial family that has evolved convergently with cats.

The marsupial lion specimen numbered WAM 02.7.1 was found in Flight Star Cave | Wells, Roderick T., and Aaron B. Camens. / Plos one (2018)

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01

“Lion” is a spectator?

The marsupial lion belongs to the order Diprotodon and the suborder Pomfretia, and is a relative of the scimitar. Although it is not very famous, its fossils have a long history of discovery. The earliest marsupial lion fossil discovered was a skull, which was unearthed in the 1840s and then given to British paleontologist Richard Owen. This Owen is a big figure in the history of paleontology, and the word dinosaur was coined by him. In 1859, Owen published a paper on the marsupial lion. Owen found that its premolars were shaped like blades, and he determined that this was a characteristic of carnivores. He called the marsupial lion "one of the fellest and most destructive of predatory beasts."

Thylacoleo skull | Anderson, C. / Records of the Australian Museum (1929)

More than a hundred years have passed, and the debate and disagreement about the marsupial lion may be one of the most in the history of paleontology. Some people think it is a scavenger like a hyena, some think it is good at climbing trees like a leopard, some think it likes to steal crocodile eggs, and some think it is a "bad guy" who snatches kangaroo children (when a kangaroo is chased, the baby in the bag may accidentally fall out due to muscle contraction). The most interesting hypothesis was proposed by C. Annderson in 1929. He insisted that the marsupial lion was a vegetarian, but the teeth of the marsupial lion were not suitable for eating grass. So he asked a botanical expert and learned that there are many wild melons in Australia, and the fruit can reach 3 inches (about 7.5 cm) in diameter. So he decisively proposed that the marsupial lion could use its blade-like premolars to crack the melon rind and then swallow the melon seeds inside whole...

Aren't you afraid of melon sprouts growing in your stomach? | Doraemon

There are many debates about the marsupial lion, not because of the lack of fossil evidence. The fossils of the marsupial lion are quite numerous and complete, and there is other evidence to prove its existence. For example, the marsupial lion's "cat scratching board". In a cave called Tight Entrance cave, scientists found thousands of claw marks on limestone and mineral deposits, the largest of which must have been left by the marsupial lion. There are even pictures: in 2008, on the northwest coast of Kimberley, Australia, someone discovered a rock painting of a marsupial lion left by the aborigines, and the "cat eggs" can still be vaguely seen. This two-dimensional marsupial lion has many stripes on its body, which may reflect the true fur color that cannot be preserved by fossils. Perhaps it is more appropriate to call the marsupial lion a marsupial "tiger".

Marestail lion painted on rock | Akerman, Kim, and Tim Willing / Antiquity (2009)

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02

Big teeth bigger than mahjong tiles

The marsupial lion weighs about 100-130 kilograms, slightly smaller than a lion, with sturdy forelimbs and neck, and a long tail that is slightly like a kangaroo. It has a sturdy physique, and its calves are shorter than its thighs, which means that it is not fast and is not good at chasing. But it is good at rock climbing. Some of the marsupial lion scratches found in the cave even reached 3 meters high. The current mainstream view is that the marsupial lion is a ferocious predator. However, the marsupial lion is not a replica of the lion. Its various characteristics as a predator are different from those of real cats, which shows the evolutionary process of different paths leading to the same destination.

The most important feature of carnivores is the carnassial, which has sharp edges and is suitable for cutting meat. In the Carnivora order, including the cat family, the carnassial is a specialization of the fourth premolar in the upper jaw and the first molar in the lower jaw, while the carnassial of the marsupial lion is the third premolar in the upper and lower jaws, and it is extremely large. When the marsupial lion bites, the upper carnassial is outside the lower carnassial, rubbing against each other to keep it sharp, like two guillotines.

The marsupial lion had tiny canines but huge premolars and incisors | Beclectic / Wikimedia Commons

The lion's most important weapon, the sharp canine teeth, is almost non-existent in the marsupial lion. The marsupial lion only has two upper canine teeth, which are pitifully small. As a replacement, its front four incisors, which are the most conspicuous four large teeth on the face of a mouse, are extremely slender and sharp, and protrude forward, as if they need braces.

Other parts of the marsupial lion's body also show characteristics that are both cat-like and non-cat-like. The first segment of the marsupial lion's toes can be flexibly lifted, indicating that it can retract its claws like a cat. Its elbow joint is more flexible than that of carnivores, between wombats and arboreal animals, which also allows its forearms to move greatly. So the marsupial lion can also use the "cat punch" - like cats, use its front legs to grab prey.

The front paw of a marsupial lion. Note the large thumb. | Finch, ME and Freedman, L. / Aust. J. Zool. (1988)

However, it has a unique weapon that cats definitely don't have: the marsupial lion's thumb is particularly thick and its claws are also very large. This weapon is different from all carnivores and is more like the claws of Deinonychus. In addition, the marsupial lion's large tail may play a supporting role like the tail of its distant relative, the kangaroo, helping it to stand on its hind legs and strike with its two claws suspended in the air.

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03

Muscular but simple-minded

Although the crooked teeth are somewhat funny, the skull anatomy of the marsupial lion shows that it had very strong jaw muscles and "terrible" teeth. The bite force of the front teeth of the marsupial lion's mouth is estimated to reach 1692N, which exceeds the strongest bite force of the land carnivorous polar bear today. The bite force quotient (a data calculated by bite force and weight, indicating whether the bite force of this carnivore is large or small relative to its physique) is as high as 194. The bite force quotients of the beasts we are familiar with that hunt large prey, such as lions, tigers, wolves, etc., are mostly between 110 and 130.

Reconstruction of the skeleton and body structure of the marsupial lion | Wells, Roderick T., and Aaron B. Camens. / Plos one (2018)

The teeth at the front of the mouth (canines for Carnivora, large teeth for Marsupialos) are weapons for biting prey. If a carnivore has a strong bite force relative to its body size, and it is at the front of the mouth, it generally means that it is a tough guy who is good at hunting large prey. The bite force quotient of carnivorous marsupials is generally greater than that of Carnivora. One reason may be that the space occupied by jaw muscles and brain capacity is in conflict with each other. In other words, if the muscles are big, the brain cannot be big. The brain capacity of marsupials is generally smaller than that of placental mammals. The brain capacity of Carnivora is two and a half times that of marsupials of the same size - so the teeth of Marsupialos are so powerful because it uses muscles instead of brains.

References

[1] Akerman, Kim, and Tim Willing. "An ancient rock painting of a marsupial lion, Thylacoleo carnifex, from the Kimberley, Western Australia." Antiquity 83.319 (2009): 1-4.

[2] Anderson, C. "Macropus titan Owen and Thylacoleo carnifex Owen." Records of the Australian Museum 17 (1929): 35-49.

[3] Arman, Samuel D., and Gavin J. Prideaux. "Behaviour of the Pleistocene marsupial lion deduced from claw marks in a southwestern Australian cave." Scientific Reports 6.1 (2016): 1-8.

[4] Minard, Pete. "Making the 'Marsupial Lion ': Bunyips, Networked Colonial Knowledge Production between 1830–59 and the Description of Thylacoleo carnifex." Historical Records of Australian Science 29.2 (2018): 91-102.

[5] Wells, Roderick T., and Aaron B. Camens. "New skeletal material sheds light on the palaeobiology of the Pleistocene marsupial carnivore, Thylacoleo carnifex." Plos one 13.12 (2018): e0208020.

[6] Wroe, Stephen, Colin McHenry, and Jeffrey Thomason. "Bite club: comparative bite force in big biting mammals and the prediction of predatory behavior in fossil taxa." Proceedings of the Royal Society B: Biological Sciences 272.1563 (2005): 619-625.

Author: Red Queen

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