The Exotic Animals of Prehistoric Australia

From carnivorous kangaroos to marsupial lions, the animals of prehistoric Australia were among the most unusual that ever lived.

When Europeans first arrived in Australia four centuries ago, they must have been astounded by the unique fauna endemic to the newly discovered land. Ever since, the world down under has drawn in visitors from far and wide, equally fascinated by its exotic animals. However, thousands of years before Western explorers set foot upon the land, Australia was perhaps even more unusual.

Australia’s unique biota is a result of its isolation from the rest of the world. Until it split away from Antarctica sometime between 34 and 50 million years ago, the continent’s flora and fauna has taken its own evolutionary path. Many other areas of the world have enjoyed long periods of biological isolation, such as South America until the Great American Interchange.

Australia, still manages to retain much of its evolutionary isolation, despite the devastation caused by introduced species and other human-induced factors. The overwhelming majority of its mammals, reptiles and amphibians are endemic to the continent.

Marsupial Rise to Dominance

Wikimedia Commons

Marsupials are the dominant mammals in Australia, unlike the rest of the world where placental mammals rule.

Marsupials, known for raising their young in abdominal pouches, occupy many important ecological niches in Australia. By contrast, there are relatively few native placental mammals, despite the fact they dominate every other mammalian niche in the world. In fact, more than two thirds of all the world’s marsupial species are native to the Australasian continent, which also includes New Guinea and nearby islands. The rest are found in the Americas, particularly South America. However, it wasn’t always this way.

Marsupials have been around for much longer than placental mammals, which only first appeared shortly after the extinction of the dinosaurs 66 million years ago. It’s now widely believed, however, that all the world’s extant marsupials originated in South America, crossing over into Australia around 50 million years ago when both continents were joined by an ice-free Antarctica.

While most marsupials that were once endemic to South America went extinct during the Great American Interchange, no such event took place in Australia. In fact, it remained almost entirely isolated from the rest of the world until as recently as 48,000 to 60,000 years ago when the first humans arrived in the region.

Rom-diz

Thyalacoleo, popularly known as the marsupial lion, likely preyed upon the herbivorous diprotodon.

Prehistoric Australia was home to some mammals that put today’s marsupials to shame. Among them were the diprotodontids, a family of enormous grazing animals which, in the case of the diprotodon, grew as large as the largest rhinoceroses. Although diprotodon went extinct around 46,000 years ago, other genera survived until much later, with the last of these bizarre creatures disappearing as recently as 11,000 years ago.

Nobu Tamura

Palorchestes is sometimes known as the marsupial tapir, owing to its similar appearance to the unrelated animal.

Coexisting with diprotodon and no doubt preying upon it was the so-called marsupial lion. Except that it wasn’t related in any way to any felid that ever lived. In a perfect example of convergent evolution, the marsupial lion or, more correctly, thylacoleo, vaguely resembled a lion owing to the similar ecological niche it was adapted to. According to research, this once immensely successful and specialized apex predator had the largest bite force relative to its body weight of any mammal that has ever lived. Though it weighed little more than an adult human, its bite was comparable to that of a lion.

Nobu Tamura

Zygomaturus was superficially similar to a pygmy hippopotamus both in size and weight.

As it does today, marsupial dominance extended to just about every terrestrial mammalian niche throughout Australia. Giant prehistoric kangaroos weighing upwards of 550 pounds (250 kg) roamed the land alongside the even larger zygomaturus, an enormous wombat-like creature that wallowed in wet coastal regions until around 45,000 years ago. Palorchestes, another large herbivorous marsupial, grew to the size of a pony and had a bizarre proboscis giving it the nickname ‘marsupial tapir’.

Thunder Birds and Monster Lizards

Monash University Gippsland

Megalania, the largest terrestrial lizard that ever lived, attacks a nest belonging to the flightless Bullockornis.

Giant marsupials didn’t exclusively dominate prehistoric Australia. Until some 40,000 years ago, the continent was home to an animal that looked like something belonging to the time of the dinosaurs. Megalania is a true champion in the world of land-dwelling lizards in that it’s the largest ever known. A varanid (monitor lizard), megalania grew as large as a saltwater crocodile and may have preyed upon animals as big as diprotodon. It is possible that megalania was also venomous.

In seemed that almost every class of terrestrial animal had its gargantuan representatives in prehistoric Australia, and birds were no exception. Extant Australian ratites, such as emus and cassowaries, can grow around 6 feet (1.8m) high, but some prehistoric variants were even bigger. One was the rather facetiously nicknamed demon duck of doom (Bullockornis), an 8”2’ (2.5m) tall flightless bird that lived 15 million years ago. Even larger was the much more recent dromornis, which may have also been carnivorous.

JJ Harrison

Having appeared at about the same time as the dinosaurs, monotremes are among the oldest and most primitive mammals on Earth.

Perhaps the most peculiar of all Australia’s prehistoric animals was zaglossus hacketti, a giant echidna that weighed up to 66 pounds (30 kg). This odd creature has the distinction of being the largest monotreme ever known to exist, although it’s only known from a few fragmented fossil remains. Being a monotreme to start with is pretty unusual – there are only five species of these bizarre, egg-laying mammals left in the world (the platypus and four types of echidna). Monotremes, however, may be the oldest true mammals on Earth, with some estimates putting their evolution back to the Triassic-Jurassic boundary 200 million years ago!

What Happened to Australia’s Fantastic Fauna?

Most of Australia’s prehistoric giants disappeared between 45,000 and 10,000 years ago, which happens to coincide with the suspected arrival of the first Australian aborigines. There’s little doubt that the early aborigines coexisted with animals like the marsupial lion and the last diprotodontids. In fact, it’s likely that some of these prehistoric animals may have inspired aboriginal mythology, and certain cave paintings are also thought to depict long-extinct beasts.

Although ancient climate change, particularly increasing aridity, has often been blamed for the disappearance of much of Australia’s megafauna, new evidence suggests that humans might be to blame after all. This shouldn’t really come as a great surprise, since the wave of extinctions befalling America’s prehistoric megafauna also coincides with the proliferation of humans in those areas.

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Unfortunately, as has been the case throughout the Holocene, it seems that many among these unique animals fell victim to the world’s greatest super predator – humans. Nonetheless, Australia’s prehistoric giants were among the most unique creatures to exist since the time of the dinosaurs. What are your favourite creatures from ancient Australia? If you can think of any exotic taxons I haven’t covered here, feel free to mention them in the comments!

Further Reading