A fossil found in Spain is likely that of the world's oldest flower, blooming on an aquatic plant that grew 130 million years ago, paleobotanists say.

Montsechia vidalii, a Cretaceous Period plant around at the time of the first feathered dinosaurs, grew in abundance in freshwater lakes that once existed in what are today mountainous areas in Spain, they say.

As the earliest known flower it's slightly older than another one, Archaefructus sinensis from China, researchers report in the Proceedings of the National Academy of Sciences.

"A 'first flower' is technically a myth, like the 'first human,' " says Indiana University paleobotanist and study co-author David Dilcher, who has studied the origins of flowering plants for decades. "But based on this new analysis, we know now that Montsechia is contemporaneous, if not more ancient, than Archaefructus."

The plant would have been growing in a landscape shared with dinosaurs like Iguanadon and Brachiosaurus, the researchers say.

It meets the definition of a flowering plant, also known as an angiosperm, because it produced seeds inside a carpel, a flower's female reproductive organ.

However, it would not have looked like what the word flower brings to mind today, Dilcher acknowledged.

"Montsechia possesses no obvious 'flower parts,' such as petals or nectar-producing structures for attracting insects, and lives out its entire life cycle under water," he explained. "The fruit contains a single seed" – the defining characteristic of an angiosperm – "which is borne upside down."

The modern plants it most would have resembled are Ceratophyllum, whose common name is hornworts, dark green aquatic plants often used as a decoration in aquariums.

Montsechia comes from a time in the Cretaceous period that saw an explosion of diversity in flowering plants, creating the colorful blooms we see today and influencing animal species that evolved along with them.

Without such plants, we wouldn't be here, Dilchers says.

"We are a product of the many stages of evolution that went hand-in-hand with the evolution of flowering plants," he says.

Although Montsechia can, for the moment, claim the title as the oldest known flowering plant, there may be older ones waiting to be identified in the fossil record, says study co-author Bernard Gomez of Claude Bernard University in Lyon, France.

Fossils have suggested the presence of pollen as far back as 140 million years, he says.

For now, the scientists say they will focus on Montsechia to see what secrets of ancient plant life it may reveal.

"This plant shows us where it all began," says Dilcher.

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