Context

• Scientists have spotted in rocks from northern China what may be the oldest fossils of a green plant ever found, tiny seaweed that carpeted areas of the seafloor roughly a billion years ago and were part of a primordial revolution among life on Earth.
• The plant, called Proterocladus antiquus, was about the size of a rice grain and boasted numerous thin branches, thriving in shallow water while attached to the seafloor with a root-like structure.
• Proterocladus - a form of green algae - was one of the largest organisms of its time, sharing the seas mainly with bacteria and other microbes. It engaged in photosynthesis, transforming energy from sunlight into chemical energy and producing oxygen.
• Proterocladus antiquus is a close relative of the ancestor of all green plants alive today. The fossils were detected in rock dug up in Liaoning Province near the city of Dalian.
• The first land plants, thought to be descendents of green seaweeds, appeared about 450 million years ago.
• There was an evolutionary shift on Earth perhaps 2 billion years ago from simple bacteria-like cells to the first members of a group called eukaryotes that spans fungi, plants and animals. The first plants were single-celled organisms.
• Proterocladus is 200 million years older than the previous earliest-known green seaweed. One of its modern relatives is a type of edible seaweed called sea lettuce.
• Proterocladus represents the oldest unambiguous green plant fossil. Fossils of possible older single-celled green plants are still a matter of debate.