Until 140 million years ago, there were no flowers anywhere on Earth. Then, primitive flowers burst onto the scene, and flowering plants took over the world.

All living flowers today came from a single ancestor that lived about that time, according to a new study published Tuesday in the peer-reviewed British journal Nature Communications.

Scientists also reconstructed what they believe that first flower looked like: Somewhat similar to a water lily, with circles of broad petals around a center of protruding pollen spikes.

However, lead author Hervé Sauquet, an evolutionary biologist from Paris-Sud University, said it's difficult to make a direct comparison with flowers of today: "All flowering plants have evolved and changed since that ancestor, that's how evolution works," he said. "So there is no single species or group of species that would have existed some long time ago and still exists today unchanged."

The study used an evolutionary tree to connect all living species of flowering plants, which was based on genetic data from 792 species.

The origin and early evolution of flowering plants and especially their flowers have long been one of the biggest enigmas in biology, almost 140 years after Charles Darwin called their rapid rise in the Cretaceous "an abominable mystery."

The ancestral flower was bisexual, with both female (carpels) and male (stamens) parts, and with multiple whorls (concentric cycles) of petal-like organs, in sets of threes, according to the new study.

About 20% of flowers today have such "trimerous" whorls, but typically fewer: lilies have two, magnolias have three. "These results call into question much of what has been thought and taught previously about floral evolution," said study co-author Juerg Schoenenberger of the University of Vienna. "It has long been assumed that the ancestral flower had all organs arranged in a spiral."

Study co-author Maria von Balthazar, another University of Vienna scientist, said "the results are really exciting! This is the first time that we have a clear vision for the early evolution of flowers."

No flower fossils exist from 140 million years ago, though, Sauquet said. The fossil record of flowering plants is still very incomplete, he said, and scientists have not yet found fossil flowers as old as the group itself. The earliest flower fossil is "only" 130 million years old.

As for where that original flower 140 million years ago came from, Sauquet said that "we're not sure, and that remains one of the biggest mysteries in plant science. We know it came deep down from a common ancestor with all gymnosperms (conifers, cycads, ginkgo), maybe 310 million years ago.

"But we don't know yet what that ancestor looked like, nor what happened in between these two ancestors, a period of time some of us like to refer to as a 'dark tunnel,'" Sauquet said.

William Crepet, a plant biologist at Cornell University who was not involved in the study, told The Guardian that while he had some reservations about the model used in the study, the results were interesting and raise questions about the ancestry of the flowering plants.