Inside Australia’s Giants: The Real Life Drop Bear
Australia, 50,000 years ago.
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| 55 million years of island isolationism created this graphic landscape. Terrestrial life in the "Great Southern Land" would be at its largest at the end of the Pleistocene. Image via the world renowned palaeo-artist, Peter Trussler. |
The sun is intense. There's been no reprieve from the heat for the last few days, as sweat glistens on your forehead and flies land on every inch of your body. You're tired; but something has been preventing you from sleeping. For the last few nights, blood curdling screams from an other-worldy creature have pierced the dead silence.
This dry season has been an exceptionally intense one. You look around. Eucalypts dominate the surrounding parched red plain, with small interspersed shrubs and an assortment of weird animals. A small billabong is attracting the megafauna from all around. You see familiar faces on the far side of the water. A mob of red Kangaroos rest in the shade of small salts bushes, licking their forearms. Even sulphur crested cockatoos squabble amongst themselves up on the highest branches... but alongside them, unlike anything seen in the modern world.
A matriarchal herd of four legged wombat-like creatures (the size of hippos!) quench their thirst. These are the Diprotodontids, the largest of all marsupials. They let off low, guttural grunts to one another, excited by the presence of water after their long migration.
In the distance, a low rumbling noise startles you and immediately, the pitter-patter of gentle rain follows. It's still hot. You go down to the billabong, under the presence of a huge Eucalyptus tree. Strange grooves and markings adorn the multi-coloured tree trunk that you've never seen before. They look like claw marks.
20 metres away to your left, another strange megafauna stumbles up to the waters edge; a gigantic variety of kangaroo, known as a Sthenurine. With a face pushed in like a pug, but standing taller than a fully grown man, it looks formidable.
You cup your hands together and place them in the cool, refreshing water. Then, out of the corner of your eyes, you see it. A four legged blur jumps down onto the Sthenurine, as its skull hits the ground in one swift moment. Crack. The striped predator pins the kangaroo down to the ground with its immense weight. The Sthenurine squeals repeatedly in terrified pain, as the cat-like predator digs its claws deep within its tufted grey fur, penetrating the soft underbelly in an attempt to disembowel it. The giant Diprotodontids nearby hobble away as quickly as they can, the low guttural grunts turning into screeches of total panic. Within a matter of seconds, this immense predator uses its bolt-cutter like teeth to embrace the kangaroos delicate neck and squeezes the life out of it. The gentle rain becomes a colossal downpour and within ten seconds, the fight is over.
Stunned by what you saw, you get up and run. Terrified. You sprint in the opposite direction, eyes wide open despite the rain, kicking up the water in front of you.
A blood-curdling scream emanates through the newly drenched plain.
You would not be sleeping that night...
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| Highly contentious cave art from the Kimberlies (of Western Australia) depicting Thylacoleo. With large forearms and cat-like head, some researchers have argued that this is the a first-hand depiction of the marsupial predator. Others believe it represents a Tasmanian Tiger. Image via Ackerman et al. 2009 |
When I was growing up, rumours abounded of the Australian “Drop-Bear”. This mythical creature (closely related to koalas) was a leopard sized predator with horrific, bone crushing fangs and powerful muscled forearms that allowed it to ambush medium-sized kangaroo prey from the treetops. We know that this animal doesn't exist in modern times, but I jokingly warn tourists to look out for them from time to time (and slather Vegemite behind their ears). But when the first Australians arrived on the continent (some 50,000 - 85,000 years ago… it’s hugely controversial…), they came face to face with this drop bear; a marsupial super-carnivore that had reached proportions similar to a Lioness on the Serengeti. This post will focus on the anatomy of the largest marsupial carnivore that ever lived in Australia; the late Pleistocene Thylacoleo carnifex, the Pouched Marsupial Lion.
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| "Daddy, do you hear that?" As the small family sits around the campfire, they were blissfully unaware of what was behind them... Image via Andrew McMillan. |
Thylacoleo was extreme in almost every respect. There’s so much to focus on… from its bizarre dentistry (and subsequent strong bite force*), to its powerfully built forearms and its semi-opposable thumb, with sharp claws to match. Thylacoleo was a truly terrifying beast. But first, lets focus on the weapon that made this animal infamous: its teeth…
*Note: This bite force ("the strongest of any mammalian lineage") has been hugely contested as of late.There's no doubt it was strong, but more reliable work needs to be done before we can make this statement.
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| Look down at your hand. Open it wide. This is the size of this jaw. Image via Richard Owen. |
Teeth
Nestled within the jaw of this predator is the elongated stabbing incisor, followed by the hugely exaggerated carnassial (premolar), a tooth adapted for slicing the flesh off prey and even crushing bone.
The molars are hugely reduced, to mere “nubs” and this dental formula may have proved problematic to Thylacoleo; did they need a strong bite force to offset the ridiculous arrangement of its teeth? There’s no animal in the modern world that has a dental formula that even comes close to Thylacoleo, so all we can do is hypothesize. It’s entirely possible, but in order to answer this question we need to understand more about its anatomy; the legs of this creature tell a crazy story of hyper-carnivory…
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| This image seems a little exaggerated, but even so, check out that claw! You could put somebody's eye out with that thing! Image via Adrie and Alfons Kennis |
Forearms/Backlegs
Some have even argued that we have first hand accounts of this mega-carnivore. The hugely controversial rock art depiction (~40,000-50000 years old) shown in the second image demonstrates a greatly exaggerated forelimb when matched to the hind limbs. This apparent asymmetry is not seen in rock art images of Thylacines, where both hind and fore limbs are usually of similar dimensions. Based off nearly complete specimens found in the Nullarbor, the forearms are much more robust than the hind limbs for this hyper-carnivore. But why is this so? In order to understand this disparity, we need to look at Thylacoleo’s claws…
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🤙 Image via Borja Figueirido, displaying the hand of the Marsupial Lion |
Claws
*The literature states that this creature had retractable claws. But after discussion with a few colleagues, it was pointed out to me that this is utter nonsense; there is no anatomical basis for these animals having retractable claws like felines.
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| Check out the stripes. They make you go faster, right?? Image via Peter Schouten. |
When anatomists (such as Sir Richard Owen) first encountered the remains of Thylacoleo, its diet posed a mystery. Some concluded that it was a melon eating herbivore, but there’s no doubt (based off its teeth, skull and post crania) that this creature was a ferocious predator. Its disappearance is still an ongoing mystery, but increasingly dry conditions (that began in Australia some 350,000 years ago) would have shrunk the continent’s woodlands, causing populations of forest prey to dwindle. This would have left the marsupial lion vulnerable to extinction. It crunched into its last prey some 30-40,000 years ago on mainland Australia, as the last and largest of its family.
EDIT: Want to know where i got the inspiration for that story? Try sleeping with koalas.
https://www.youtube.com/watch?v=PlxnXMWO-jk
References
Wroe, S., et al. "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 (1999): 489-498.
Finch, M. E., and L. Freedman. "Functional-Morphology of the Limbs of Thylacoleo-Carnifex Owen (Thylacoleonidae, Marsupialia)." Australian Journal of Zoology 36.3 (1988): 251-272.
Figueirido, Borja, Alberto Martín-Serra, and Christine M. Janis. "Ecomorphological determinations in the absence of living analogues: the predatory behavior of the marsupial lion (Thylacoleo carnifex) as revealed by elbow joint morphology." Paleobiology 42.3 (2016): 508-531.
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.
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