Procoptodon, also known as the Giant Short-faced Kangaroo. It lived in Australia and went extinct with other Australian megafauna after humans reached Australia 50,000 years ago. Procoptodon, Peter Trusler
Diacodexis lived from about 55 to 46 million years ago and fossils of it were found in Europe, America and Asia. it's difficult to be certain about the species that existed. It was at any rate a small critter, 60 cm/2' long in total of which the long tail made up a good part. It had fairly long legs and was probably a good runner, although the artiodactyls that came later became much better adapted at running and leaping.