Well after the mass extinction at the end of the Cretaceous Period, which saw the demise of giant land-dwelling dinosaurs and ocean-going marine reptiles, a new wave of giants evolved on the planet. The “Megafauna” were the giants of their time, giant versions of what we see today, from almost every animal group. Giant frogs, lizards, snakes, birds and mammals. Some megafauna live today, such as the Elephant, Rhinoceros, Whales and crocodiles.
Australia has a few remaining native megafauna, such as the Red Kangaroo, Emu and Estuarine Crocodile, whilst the oceans that surround our continent are home to the largest living marine megafauna, like the Blue Whale, Giant Squid, Whale Shark and Leather-back turtle. However, Australia didn’t always have so few native megafauna, instead our island continent was once home to the largest ever monotremes (egg-laying mammals), marsupials (pouched mammals), lizards and birds. Evidence of these extinct megafauna can be found across Australia as fossilised remains found in deep dark caves, eroding from river and creek banks, in ancient swampy peat bogs and dried-up salt lakes, and even eroding from old beach dunes.
Megalania (Varanus priscus)
Australia is a land of reptiles, possessing diversity unlike anywhere else on Earth. Australia’s native reptiles range in size from tiny worm-like blind snakes less than 10cm long to giant estuarine crocodiles, up to 7m long. During the Pleistocene, Australia was home to the largest land-dwelling reptiles since the time of the dinosaurs.
The largest-ever land-dwelling lizard was an animal named Megalania, which was related to goannas and reached a whopping 5-6m in length, two to three metres longer than the largest living lizard species, the Komodo Dragon, Varanus komodoensis. These giant three metre goannas were present in Australia over three million years ago, whilst Megalania may have encountered the first humans to arrive in Australia, around 50,000 years ago.
Diprotodon (Marsupial ‘Bear’) was the largest marsupial to ever live and looked like a giant wombat. This animal was 3-4m long and was nearly 2m tall at the shoulder. Diprotodon was a plant eater, feeding on low shrubs and grasses. As a marsupial, diprotodons would have carried a single enormous joey in moderate-sized herds as kangaroos do today. One fascinating fact about it’s biology was that Diprotodon had continuously growing front teeth (or tusks) that it used to shred bushed and grasses, making them easier to eat. Fossils of Diprotodon have been found in the Winton and Birdsville districts, including a complete lower jaw and a fragmentary upper jaw. Currently there is debate surrounding the presence of one or two species of Diprotodon. The fossils found from central Queensland will be used to resolve the identity of one of Australia’s iconic prehistoric animals.
Pallimnarchus and Quinkana
Australia’s largest living reptile is the estuarine crocodile, Crocodylus porosus, that inhabits the rivers, estuaries and oceans of northern Australia. A smaller species, Crocodylus johnsoni, is found in freshwater rivers in northern Australia. However, during the Pleistocene, several other species of crocodile are known to have lived in freshwater rivers and lakes throughout central and eastern Australia much further south and farther inland than modern species do today. One giant freshwater crocodile, named Pallimnarchus, has been found throughout central Australia, from southern Queensland up to Cape York Peninsula. Pallimnarchus was a very large crocodile with a broad-snout, massive conical stabbing teeth and large plates of bone underneath its skin, called osteoderms. These osteoderms were used in defence from attacks from other territorial Pallimnarchus.
Fragmentary fossils of another crocodile, named Quinkana, have been found in cave and creek fossil sites throughout Queensland. The shape of the skull and teeth of Quinkana, and the skeletons of closely related species, suggest that it was land-dwelling. Fossils of Quinkana have been found within caves that are considerable distances from ancient water courses, and within rugged terrain, therefore, Quinkana must have been better able to travel across land than other crocodiles of the time. Perhaps it actively hunted on land like Megalania.
Procoptodon (Giant Short-faced Kangaroo) was the largest kangaroo to ever live, standing 8 feet tall and possessing a truly bizarre body-shape. Unlike modern day kangaroos Procoptodon had an extremely short face, almost human-like, enormously long and strong forearms, robust and muscular legs and a short thick tail. Procoptodon was not built for excessive hopping, in fact, it would have used its long arms, strong legs and thick tail to balance itself whilst it pulled down large branches from trees, stripping them of their new leaves to feed such a bulky body. Fossils of this giant have been found in the Winton district, preserved as fragmentary teeth and a possible pelvis.
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