Perhaps as few as 20 000 to 25 000 years ago a number of large-sized animals roamed much of Australia, including the area around the Murray River region. Just what caused their extinction is unresolved, but both climate and human intervention were probably part of the answer. All that remains today are their small relatives, the kangaroos, wombats and the emus.
Diprotodon was the largest of all marsupials, an animal with no real modern counterpart. It stood about 2 metres at the shoulder and was 3 or more metres in length. Being a marsupial it most likely carried its young in a pouch. It grazed on rather tough vegetation that characterised inland Australia during the Pleistocene times (164 million to 10 000 years before present). At Lake Callabonna in eastern South Australia whole skeletons have been recovered.
Sthenurus was a large browsing kangaroo that lived for the most part in the savannah regions of the southern quarter of Australia, including the Murray River region.
Living alongside Sthenurus was a remarkable group of birds called the Mihirungs. Although thought by some to be just large emus, Mihirungs were probably at best only distantly related to them, but more likely related to the game birds such as mallee fowl and scrub turkeys. The last surviving Mihirung, Genyornis newtoni, is the best known from Lake Callabonna although it roamed across much of Australia. It stood about the height of a tall human, perhaps slightly taller. Genyornis could not fly, and its wings were reduced to small structures.