Professor Shuhai Xiao of Virginia Tech university in the US, said: “These new fossils suggest that green seaweeds were important players in the ocean long before their land-plant descendants moved and took control of dry land.
“The entire biosphere is largely dependent on plants and algae for food and oxygen, yet land plants did not evolve until about 450 million years ago.
“Our study shows that green seaweeds evolved no later than one billion years ago, pushing back the record of green seaweeds by about 200 million years.”
He added that the current hypothesis is that land plants like trees, grasses and food crops, evolved from green seaweeds – aquatic plants.
“These fossils are related to the ancestors of all the modern land plants we see today,” Prof Xiao said.
However, not all geobiologists agree on the origins of green plants, with some suggesting they started in rivers and lakes, before conquering the ocean.
The researchers suggest the tiny seaweeds once lived in a shallow ocean, died and then became “cooked” under a thick pile of sediment, preserving their shape.
According to the scientists, the seaweeds’ multiple branches, upright growth and specialised cells suggest the fossil is a green seaweed that is about one billion years old.
Reader Q&A: Which came first, the plant or the seed?
Asked by: Adam King, Huddersfield
The earliest fossils of complex land plants date from around 470 million years ago. They resembled liverworts – a kind of simple moss – and reproduced by releasing spores, which were carried away when it rained.
Spores contain a single cell, whereas a seed contains a multicellular, fertilised embryo that is protected from drying out by a tough coat. These extra features took another 150 million years to evolve, whereupon the first seed-bearing plants emerged. So plants came first, by a long way.
Alexander is the Online Editor at BBC Science Focus and is the one that keeps sciencefocus.com looking shipshape and Bristol fashion. He has been toying around with news, technology and science on internet for well over a decade, and sports a very fetching beard.