The History of Life on Earth: What Are Fossils?

Fossils are tangible remains or signs of ancient life forms that have been preserved in sedimentary rocks. The history of life on our planet can be considered to be written in them.

The History of Life on Earth: What Are Fossils?
Fossils of the world's three largest sea creatures found in the Alps. Image: courtesy: (screen capture YouTube/PaleoCronicas)