Flowers appeared on Earth 100 million years earlier than was previously thought, according to evidence from ancient fossilised pollen grains.
The beautifully preserved pollen, found in cores drilled from a site in northern Switzerland, is dated to 240 million years ago.
Until recently scientists were convinced flowering plants only emerged in the Early Cretaceous period around 140 million years ago, when dinosaurs ruled the Earth.
In 2004 scientists identified much older flowering plant-like pollen from cores from the bottom of the Barents Sea, south of Spitsbergen in Norway, but the evidence was not conclusive.
The new find appears to confirm an ancient origin for flowering plants, or angiosperms, which evolved from extinct cousins of conifers, ginkgos, cycads and seed ferns.
It also suggests the primitive flowers were blossoming across a broad ecological range.
During the Middle Triassic period, more than 200 million years ago, the Barents Sea and Switzerland were subtropical environments, but the area encompassing Switzerland was much drier.
This indicates that even by this stage flowering plants were adapting to different conditions.
The new research, led by Dr Peter Hochuli from the University of Zurich, appears in the latest issue of the journal Frontiers in Plant Science.
The authors wrote: "Together with the previously published records from the Middle Triassic of the Barents Sea area, the angiosperm-like pollen grains reflect a considerable diversity of the parent plants during the Middle Triassic."
The structure of the grains suggests the plants they came from were pollinated by insects, said the researchers.
These were most likely to have been beetles, since bees did not evolve for another 100 million years.