3.4 million years old… oh boy!

In Australia, researchers have discovered fossils of microbes that are 3.4 million years old. The fossils, known as stromatolites, range in size from being smaller than a fingernail to taller than a man. These stromatolites are the same as what astrobiologists are looking for on Mars and other places for signs of life. They're produced layer by layer when dirt sediments mix with carbon dioxide expelled from bacteria, water, and minerals — all trapped in the microbes' sticky mucilage.
This article relates back to when dinosaur fossils were first discovered in the nineteenth century. It opened up a whole new world for scientists, enabling them to trace signs of life back further than they ever had. Dinosaurs were vertebrate animals that dominated the terrestrial ecosystem for over 160 million years, first appearing approximately 230 million years ago. At the end of the Cretaceous period 65 million years ago, dinosaurs suffered a catastrophic extinction, which ended their dominance on land.