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Description

A selection of diprotodontian marsupials, known as thylacoleonids, to scale.

For all the potentially dangerous species that inhabit Australia (think sharks, crocodiles, blue-ringed octopus, stonefish, funnelweb spiders and venomous snakes), one particular aspect of the fauna is missing: large predatory mammals. Of course the southern continent was once home to the dog-like thylacines (see Wolf imposters of Down Under - Thylacinids ) but these were far from apex predators. Early indigenous settlers arriving on the continent around 60,000 ya had more to worry about from the giant reptiles (see Super-size and range in size from tiny d snakes - Madtsoiids , True Crocodiles 2 (the Australasian radiation) and Fast, smart + fierce - Varanids ). Even so, one large marsupial hunter would have sent shivers down the backs of the original human inhabitants.

Dasyuromorphians are the dominant group of carnivorous marsupials (ranging between 5 gram planigales up to the large dog-sized thylacine) with most other marsupials being largely herbivorous diprotodontians, including macropods, possums and vombatiforms (see Mega-marsupials - Diprotodontids , Might as well jump - Macropodids 1 and Might as well jump - Macropodids 2 ). However one extinct group of vombatiforms bucked this vegetarian trend. The thylacoleonids were a predominantly arboreal group of hunters with specialised hypercarnivorous dentition. Large flat shearing blades in the rear of the mouth were actually specialised premolars and convergent with the carnassial teeth found in carnivoran mammals, while the incisors at the front of the mouth were more canine-like. Together the dentition and muscle attachment gave thylacoleonids a stronger bite force than comparably-sized carnivores. Upon describing the first known fossils, Richard Owen described it amongst 'the most destructive of predatory beasts'. Heavily muscled forelimbs and retractable claws allowed them to climb trees, and it has been suggested that thylacoleonids could jump from a height on to the back of potential prey (whether this was actually possible is debatable). In addition to the above armoury, thylacoleonids had enormous hooked claws on the large semi-opposable thumbs which were used to pin down prey and dispatch it. Smaller species showed similar adaptations to possums and koalas for life among the trees in the structure of the arm and shoulder. Scratch marks in a steep-sided cave indicate that Thylacoleo also had no difficulties climbing back-and-forth. Most of the scratches were attributed to juveniles, suggesting the cave was probably used for rearing young.

Thylacoleonids are first known from the latest Oligocene and earliest Miocene ranging in size from diminutive (Microleo, Lekaneleo) tree-dwellers up to small dog-sized species (Wakaleo). From the Pliocene until late into the Pleistocene, the only surviving genus was the larger Thylacoleo. Reaching weights of up to 160 kgs, T. carnifex was the species which best fitted the title of 'marsupial lion'. Along with the giant varanid lizard 'megalania' and the mekosuchian crocodile Quinkana, Thylacoleo was the apex terrestrial predator across the continent.
In a bizarre sense of irony a popular creature of Australian folklore (dating back to the 1920s, but popular from the 80s onwards) is the dropbear, fashioned on a carnivorous version of the koala which attacks unsuspecting humans (ie. tourists) from tree branches. It turns out there was an element of truth in the joke.

Description

A selection of diprotodontian marsupials, known as thylacoleonids, to scale.

For all the potentially dangerous species that inhabit Australia (think sharks, crocodiles, blue-ringed octopus, stonefish, funnelweb spiders and venomous snakes), one particular aspect of the fauna is missing: large predatory mammals. Of course the southern continent was once home to the dog-like thylacines (see Wolf imposters of Down Under - Thylacinids ) but these were far from apex predators. Early indigenous settlers arriving on the continent around 60,000 ya had more to worry about from the giant reptiles (see Super-size and range in size from tiny d snakes - Madtsoiids , True Crocodiles 2 (the Australasian radiation) and Fast, smart + fierce - Varanids ). Even so, one large marsupial hunter would have sent shivers down the backs of the original human inhabitants.

Dasyuromorphians are the dominant group of carnivorous marsupials (ranging between 5 gram planigales up to the large dog-sized thylacine) with most other marsupials being largely herbivorous diprotodontians, including macropods, possums and vombatiforms (see Mega-marsupials - Diprotodontids , Might as well jump - Macropodids 1 and Might as well jump - Macropodids 2 ). However one extinct group of vombatiforms bucked this vegetarian trend. The thylacoleonids were a predominantly arboreal group of hunters with specialised hypercarnivorous dentition. Large flat shearing blades in the rear of the mouth were actually specialised premolars and convergent with the carnassial teeth found in carnivoran mammals, while the incisors at the front of the mouth were more canine-like. Together the dentition and muscle attachment gave thylacoleonids a stronger bite force than comparably-sized carnivores. Upon describing the first known fossils, Richard Owen described it amongst 'the most destructive of predatory beasts'. Heavily muscled forelimbs and retractable claws allowed them to climb trees, and it has been suggested that thylacoleonids could jump from a height on to the back of potential prey (whether this was actually possible is debatable). In addition to the above armoury, thylacoleonids had enormous hooked claws on the large semi-opposable thumbs which were used to pin down prey and dispatch it. Smaller species showed similar adaptations to possums and koalas for life among the trees in the structure of the arm and shoulder. Scratch marks in a steep-sided cave indicate that Thylacoleo also had no difficulties climbing back-and-forth. Most of the scratches were attributed to juveniles, suggesting the cave was probably used for rearing young.

Thylacoleonids are first known from the latest Oligocene and earliest Miocene ranging in size from diminutive (Microleo, Lekaneleo) tree-dwellers up to small dog-sized species (Wakaleo). From the Pliocene until late into the Pleistocene, the only surviving genus was the larger Thylacoleo. Reaching weights of up to 160 kgs, T. carnifex was the species which best fitted the title of 'marsupial lion'. Along with the giant varanid lizard 'megalania' and the mekosuchian crocodile Quinkana, Thylacoleo was the apex terrestrial predator across the continent.
In a bizarre sense of irony a popular creature of Australian folklore (dating back to the 1920s, but popular from the 80s onwards) is the dropbear, fashioned on a carnivorous version of the koala which attacks unsuspecting humans (ie. tourists) from tree branches. It turns out there was an element of truth in the joke.