The earliest flowering plants may have a very different form from what we previously thought, according to a new finding by a team of paleobotanists. Montsechia vidalii, an aquatic plant from 125 million to 130 million years ago, has been revealed as the earliest known plant to have had flowers.
"This discovery raises significant questions about the early evolutionary history of flowering plants, as well as the role of these plants in the evolution of other plant and animal life," study lead author David Dilcher, of the Indiana University Bloomington College of Arts and Sciences' Department of Geological Sciences, said in a statement.
The plant, fossils of which were originally discovered in limestone deposits in the Iberian Ranges of Spain over 100 years ago, had previously been thought flowerless. However, after examining the fossilised remains of over 1,000 specimens, Dilcher and his team found enough evidence to confirm that Montsechia was an angiosperm, or flowering plant.
But the flowers don't look like what you might expect.
"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," Dilcher said. "The fruit contains a single seed [the defining characteristic of an angiosperm], which is borne upside down."
The team very carefully and painstakingly applied hydrochloric acid to the fossils, drop by drop, to reveal the structure of the plants, and bleached the protective covering of the leaves using nitric acid and potassium chlorate to reveal their shape. These were then examined under a stereomicroscope, a light microscope and a scanning electron microscope.
The results were published in the journal PNAS.
The plant, which existed around the same time as the brachiosaurus and the iguanodon, may predate what had been thought was the first flower, another aquatic plant from China called Archaefructus sinensis.
"A 'first flower' is technically a myth, like the 'first human,'" said Dilcher. "But based on this new analysis, we know now that Montsechia is contemporaneous, if not more ancient, than Archaefructus."
The most modern descendant of Montsechia is an aquatic angiosperm called Ceratophyllum, which is popular in freshwater aquariums. The next step is to try to understand more about the relationship between Montsechia and Ceratophyllum, as well as other land-based angiosperms. Although evidence implicates that some aquatic plants have early flowering plants as ancestors, its unlikely that they all evolved from aquatic ancestors, the paper concludes.
"There's still much to be discovered about how a few early species of seed-bearing plants eventually gave rise to the enormous, and beautiful, variety of flowers that now populate nearly every environment on Earth," Dilcher said.