A study in Science reports that Late Cretaceous flowering plants already carried seeds inside fleshy, fruit-like structures and winged diaspores more than 74 million years ago—before the end of the dinosaur era. Fossil evidence from south-central New Mexico po
For more than a century, a simple picture dominated how scientists explained the rise of flowering plants. In the age of dinosaurs. angiosperms were thought to depend mostly on wind and other inanimate routes to move their seeds—until a catastrophic asteroid impact cleared the stage 66 million years ago.
But the fossils tell a messier story.
Over 74 million years ago, a richer “garden” of fruit- and seed-bearing plants appears to have existed than researchers previously recognized. A fossil analysis. published June 25 in Science. suggests that tall forest trees spread winged seeds and fed animals with fleshy. blueberry-sized fruits long before the reign of the dinosaurs ended.
The implications reach far beyond botany. Paleoecologist Jaemin Lee of the University of California, Berkeley, and colleagues say the findings challenge the traditional view of how angiosperms—flowering plants—spread their offspring across the late Cretaceous.
The standard timeline had angiosperms leaning heavily on wind and other non-living dispersal mechanisms until the end of the Cretaceous Period. That picture changes after the asteroid struck Earth 66 million years ago. triggering a mass extinction event that killed all nonavian dinosaurs and made way for the Age of Mammals. In that new world. angiosperms were thought to expand into a more varied. animal-friendly repertoire of seeds and fruits that were often eaten and carried away.
Lee’s team found evidence that this shift may have started much earlier.
In a challenge to that earlier narrative, the researchers analyzed fossil diaspores—structures that include fruits and seeds—from the Late Cretaceous. They examined 450 fossils unearthed from a layer of ancient volcanic ash in south-central New Mexico collected between 1992 and 2016.
The diaspores came in nearly 80 different shapes. Some had winged forms, while more than a third were fleshy, like berries. The largest were about the size of a small date.
“There are rocks with a bunch of large diaspores preserved together,” Lee says. “They make me think of trays of grapes or pistachios.”
To Brian Atkinson, a paleobiologist at the University of Kansas in Lawrence who was not involved in the work, the scale of the discovery is the point. Until now, the diversity of diaspore types prior to the extinction was thought to be low, he said, and records of large, fleshy fruits were few.
“This study suggests that bigger diaspore sizes were certainly well-established before the end of the Cretaceous,” Atkinson says. “That’s a very important finding.”
Today, animals regularly eat the fruit of flowering plants, then excrete or discard leftover seeds. The new fossils show striking similarities between ancient diaspores and modern ones. Lee and colleagues think that means Cretaceous animals—possibly some pterosaurs and extinct rodentlike mammals—would have enjoyed the fruits.
As angiosperm fruits became available, Cretaceous birds and dinosaurs, which are known to have fed on diaspores from other plant groups such as conifers, may have switched to angiosperms.
There’s also a clue from a different kind of fossil record. Fossilized, diaspore-speckled dung from the Late Cretaceous, found in previous work, suggests that vertebrates ingested diaspores. But the link to specific animals is still uncertain.
“Matching poops to their extinct producers can be challenging,” Lee says.
Even with that uncertainty, the overall pattern fits with other evidence of angiosperm evolution during the Cretaceous. Paleobotanist Selena Smith of the University of Michigan in Ann Arbor says the plants were rapidly evolving their leaves. growth forms and overall size. “It only makes sense that the reproductive structures would be similarly evolving during the Cretaceous as plants are becoming more efficient and specialized. ” Smith says.
Eventually, these plants became the dense, angiosperm-dominated forests we know today. The study suggests those forests may have had an earlier start, in a time when the local fauna looked very different.
Atkinson says the next step is to sample other fossil sites that date to the Late Cretaceous. That would help confirm that fruits and seed-bearing structures like these filled prehistoric forests around the world—turning what has long been treated as a post-extinction story into something that likely began alongside the dinosaurs.
angiosperms flowering plants fossil diaspores dinosaurs seed dispersal Science Late Cretaceous south-central New Mexico volcanic ash pterosaurs birds