Stromatolites

They may not look like much, but Stromatolites are one of the most astonishing creatures on the planet. Why? Because they are living examples of some of the oldest life forms on earth from 3.5 billion years ago! A stromatolite is a limestone structure created over thousands of years by a colony of Cyanobacteria, a blue-green algae. The ones shown here live in Hamelin Pool (Shark Bay, Australia) and are about 2,000 to 3,000 years old! It is one of only three sites on the planet where living marine stromatolites can be found. (The other two are in the Bahamas) (Sharkbay Stromatolite website)