The question of whether turtles first appeared on land or in water, remains a mystery. How they came to form hard, protective shells continues to puzzle researchers. In China, recently discovered fossils show promise, possibly to provide the answers to these questions.

The question of whether turtles first appeared on land or in water, remains a mystery.

These are fossils of primitive turtles that lived more than 220 million years ago - during the Triassic Period. It was an epoch in which dinosaurs began to dominate the Earth's surface. Fossils of prehistoric turtles have been found in Europe. Most were incomplete. Examination of the latest find, in southwest China's Guizhou province, reveals significant differences between these turtle ancestors and their modern-time descendants. The greatest distinction is the absence of a top shell. That leads researchers to conclude that turtles evolved the belly shell first.