Based on an analysis of large seeds buried under volcanic ash about 74.6 million years ago—nearly 10 million years before a catastrophic asteroid impact wiped out the dinosaurs—UC Berkeley paleobotanists reconstruct a thriving, mature forest dominated by flowering plants, many of which produced relatively large and fleshy fruits, or diaspores.

The discovery calls into question the view that flowering plants, or angiosperms, only took over the planet in the wake of the dinosaurs' extinction, when the proliferation of mammals like rodents and bats made it energetically favorable for plants to produce large, fleshy fruits that mammals could help disperse.

After the extinction, angiosperms dominated the world, forming dense forests from pole to pole under greenhouse climates where modern groups of fruit- and seed-eating birds and mammals, such as bats, rodents and primates, radiated and consumed the large diaspores.

"Our results show that, at least in some hot and humid environments during the Late Cretaceous, well before the extinction boundary by 10 million years, angiosperms were already investing more resources into individual diaspores and forming dense forests," said the lead author and UC Berkeley doctoral student Jaemin Lee.