A Graveyard in the Salt
In the arid expanse of South Australia lies Lake Callabonna, a dry salt lake that holds the grim record of a mass tragedy from the Pleistocene epoch. This is a collection of bones, but records final, desperate moments. Preserved in the baked mud are the trackways of Diprotodon optatum, the largest marsupial ever known. These trace fossils, the subject of the scientific discipline of ichnology, record the doomed march.
Diprotodon optatum was an immense herbivore, reaching up to 1.7 meters at the shoulder, over 3.8 meters long, and weighing as much as 2,800 kilograms. Its closest living relatives are wombats and koalas. During a period of intense drought approximately 50,000 to 100,000 years ago, the vast inland lakes of Australia began to vanish. The trackways found at Lake Callabonna show herds of these giant animals walking in a single direction. The accepted interpretation is that they were trudging toward the shimmering illusion of water, a mirage on the horizon of the drying lakebed. The animals became stuck in the thick, clinging mud, eventually succumbing to thirst and starvation. Hundreds of individuals perished together, their skeletons and footprints left as proof of their death.