100 MILLION YEAR OLD STROMATOLITE FOSSIL

Cretaceous ('dinosaur age') fossil Greysonia sp., a stromatolite from the Miraflores Formation, Cerra Huanaquio, Cochabamba District, Bolivia, on a perspex stand,

18.5 x 16.5 cm (297 g), polished on both sides

Stromatolites are solid mounds comprised of layers of calcium carbonate and trapped sediment formed by colonies of blue-green algae (primitive single-celled organisms). Some of them date back an astounding 3.4 billion years, making them the oldest record of life on planet Earth. By photosynthesizing and producing oxygen, they have been tremendously important in shaping the course of evolution and ecological change throughout our planet's history.