Size and Weight:
Meiolania was one of the largest, and one of the most bizarre, prehistoric turtles in earth's history: this slow-moving denizen of Pleistocene Australia not only sported a huge, hard shell, but its strangely armored head and spiked tail seem to have been borrowed from the ankylosaur dinosaurs that predated it by tens of millions of years. In turtle terms, Meiolania has proven difficult to classify, because as far as experts can tell it neither retracted its head into its shell (like one major type of turtle) nor swung it back and forth (like the other major type).
By the way, when its remains were first discovered, Meiolania was mistaken for a prehistoric species of monitor lizard. That's why its Greek name, which means "little wanderer," echoes Megalania ("great wanderer"), the giant monitor lizard that lived in Australia around the same time. Perhaps Meiolania evolved its impressive armor to avoid being eaten by its larger reptile cousin!