(information & pictures from article in WIRED.com – report by Dave Mosher)
For 1500 million years photosynthetic organisms remained in the sea. This is because, in the absence of a protective ozone layer, the land was bathed in lethal levels of UV radiation. Once atmospheric oxygen levels were high enough the ozone layer formed, meaning that it was possible for living things to venture onto the land.
Palaeontologist Shuhai Xiao of Virginia Tech, and his colleagues found their seaweed fossil specimens in a rocky outcrop discovered in China’s southern Anhui Province. Since the researchers began digging up one site about a year ago, they’ve unearthed more than 3,000 detailed specimens. “It was a very different world then than it is now, just algae and bacteria. Burrowing animals hadn’t evolved yet, so sediments on the bottom weren’t being churned up,” said Xiao. “You get these beautiful fossils as a result.”
These seaweed-like fossils unearthed in southern China may be some of the oldest plants ever discovered.
Until now the earliest definitive evidence of complex creatures resembling modern organisms was about 580 million years old. A series of fossils described Feb. 16, 2011 in Nature predates those archetypal creatures by anywhere from 20 million to 56 million years. Read the full article .
THE EARLIEST LAND "PLANTS"
The seashore would have been enormously important in the colonisation of land. In this zone algae would have been exposed to fresh water running off the land (and would have colonised the freshwater habitat before making the move to terrestrial existence). They would also be exposed to an alternating wet and desiccating environment. Adaptations to survive drying out would have had strong survival value, and it is important to note that seaweeds are poikilohydric and able to withstand periods of desiccation.
Read more about the transition to land plant.