There are three species of living wombat, but many more known only from fossils. The earliest known species seemingly lived in rainforests and fed on leaves, while later species switched to a diet of grass and developed rootless, ever-growing teeth to handle such gritty fodder. Among later forms were giants such as Ramsayia magna, estimated to weigh 100 kg, and Phascolonus gigas, which was possibly more than 500 kg.