Numerous exotic animals lived in Pleistocene Australia (1.8 million to 11,550 years BP). Many of these animals went extinct about 48,000 years ago, when humans first arrived on the continent, though some only died off as recently as the 19th century. Pleistocene Australia was one of the first places primitive humanity went after leaving Africa, as massive ice sheets made most of Europe and modern-day Russia uninhabitable.
Splitting off from Gondwanaland — an ancient continent including South America and Antarctica — some 40 million years ago, Pleistocene Australia had a chance to evolve its own unique fauna. Some of them resemble exaggerated versions of species still alive today. The primary groups are marsupials, monotremes, crocodilians, turtles, monitor lizards, and many large flightless birds.
To humans first arriving in Pleistocene Australia, one of the most conspicuous sights would have been Procoptodon goliath the Short-faced Kangaroo, a 3 meter (10 feet) tall kangaroo that weighed about 232 kg (507 pounds). This is the largest kangaroo that has ever lived. Even larger was Diprotodon, a giant wombat the size of a hippopotamus. Diprotodon is the largest marsupial that ever lived, at three meters (10 feet long) from nose to tail, two meters (6 feet) tall at the shoulder, with a weight exceeding two tonnes.
Diprotodon and the Short-faced Kangaroo would have been hunted by carnivorous animals such as the Marsupial Lion — Thylacoleo carnifex, "meat-cutting marsupial lion" — the largest marsupial predator at the time. The Marsupial Lion was 75 cm (29 in) at the shoulder and about 150 cm (75 in) long from head to tail. They averaged 101 to 130 kg (223 to 287 lb), with some reaching reaching 124 to 160 kg (273 to 353 lb) in weight. The Marsupial Lion had the most powerful bite out of any mammal, living or dead. In contrast, the largest carnivorous marsupial today, the Tasmanian Tiger, is only about the size of a dog.
Pleistocene Australia was a place with many large flightless birds, related to the carnivorous "Terror Birds" of South America. These birds, including the families Genyornis and Dromornithidae, were very fast runners, likely approaching speeds of 60 mph. Genyornis, at about 3 meters in height, may have been the largest bird that has ever lived. These birds occupied a mid-sized ecological niche that has come to be occupied exclusively by mammals in the modern world. It is unknown to which degree they were carnivorous. It may have varied among species, with some as scavengers, others are carnivores, and others as omnivores.
In the category of reptiles, Pleistocene Australia was inhabited by a 5 meter (16 ft) snake, Wonambi, named after the "Rainbow Snakes" of aboriginal mythology. This was an ambush predator, a constrictor that would have lurked around water holes, waiting for any unfortunate koala, kangaroo, or human being that came to drink. As a result, the indigenous people of Australia made it a habit to forbid their children from playing around water holes without an adult.
A gigantic monitor lizard found in Pleistocene Australia, Megalania, or "The Great Roamer," might be the closest thing this planet has had to a dragon since the end of the dinosaurs. Large specimens would have a length of 7 meters (23 ft), with a maximum conservative weight of approximately 1940 kg (4,268 lbs). This is similar to the size of an orca whale, but on land. We can only imagine what would have gone through aborigines' minds upon encountering this animal for the first time.
Other animals in Pleistocene Australia included Zaglossus hacketti, a sheep-sized echidna that is the largest monotreme yet discovered; Megalibgwilia ramsayi, a large, long-beaked echidna adept at digging; Propleopus oscillans, the "Carnivorous Kangaroo" about the size of a man; Protemnodon, a family of giant wallabies, and Quinkana, a giant crocodile.