Meganarctos

Meganarctos, also known as the giant ground koala, was the biggest koala that ever lived, it grew to about the size of a gorilla. It had a similar niche to today's Chalicotheres (especially Mesorons) and ground sloths (including Kakamoras). Its fossils suggested that it was mainly a herbivore, but by judging some of its teeth that were scraped by meat, this suggests that Meganarctos also fed on carrion of other animals. Due to its thickness of its bones and no evidence of tree-climbing features, this suggests that unlike its closest living relatives, the gentle tree koalas, Meganarctos was too large to climb trees and was a poor climber due to its weak climbing muscles, but despite this, it makes up for its strenght for defense against predators including marsupial lions, thylacines, and the extinct Megalania. It is unknown why the Meganarctos became extinct, but it possibly became extinct because of humans overhunting these marsupials or maybe humans have unintentionally spread their fire from tribes into the wilderness, burning down the native habitats of Meganarctos, burning and killing many Meganarctos, with the few survivors finally dying out to starvation. Fortunately, humans have reintroduced Meganarctos back to Australia due to time travel, which gave these giant marsupials a second chance.