By analyzing more than 1,000 fossil remains, scientists have discovered that an unassuming, 130-million-year-old water-dwelling plant could be one of Earth's first flowering plants.
Montsechia vidalii, described in the Proceedings of the National Academy of Sciences, could change many theories about how angiosperms, or plants with the ability to produce flowers, first came to be.
"Because it is so ancient and is totally aquatic," the study authors wrote, this extinct freshwater plant "raises questions centered on the very early evolutionary history of flowering plants."
Flowers are a relatively recent addition to the plant family tree; until they emerged, plants managed to reproduce without growing many-petaled lures for nectar-seeking insects.
It may seem like a complicated system – lure a bug in with flashy or fragrant flowers, get some pollen on their bodies, and hope those bugs go find another plant of the same species. But it seems to have been a highly successful evolutionary move, because soon after flowering plants are believed to have arrived on the scene, they really bloomed.
"The world of 120 million years ago was one of dynamic biological processes. During that time the flowering plants emerged as the dominant global floristic element, a transformative event that ultimately altered the character of the entire planet," Donald Les of the University of Connecticut, who was not involved in the paper, wrote in a commentary. "Understandably, the rapid rise of angiosperms has intrigued paleoecologists and evolutionary biologists, who have strived to elucidate underlying explanations for their successful radiation."
Scientists want to understand why flowering plants were so successful -- a question that Charles Darwin reportedly called "an abominable mystery." But it's hard to answer that question when you don't know what the earliest species looked like, and how they changed over time.
"Despite extensive technological advances in genetics, genomics, and bioinformatics, which have revolutionized plant research over the past decades, our comprehension of life on Earth during such ancient times continues to rely primarily on one data source: the fossil record," Les wrote.
Scientists can't even say for sure whether flowering plants first developed on water or on land.
"Some have proposed an origin in a darkened forest habitat and others an open aquatic or near aquatic habitat," Indiana University paleobotanist David Dilcher and his colleagues wrote in the new study.
Given that so few of today's flowering plants live in water, many have argued that flowers first emerged in terrestrial environments before moving to aquatic ones.
"It is generally accepted that aquatic angiosperms were derived from plants that previously lived in terrestrial environments," the researchers wrote. "Only about 2% of angiosperms are aquatic today."
That same trend seems to hold in the past as well, Les pointed out.
"Prior ecological interpretations of early Cretaceous environments have been based primarily on terrestrial plant species, which vastly dominate the paleobotanical record," he wrote.
More than a decade ago, Dilcher and fellow researchers discovered that an aquatic plant in China called Archaefructus could represent one of the earliest flowering plants. For this paper, he and colleagues turned to examine fossils of Montsechia vidalii. The first specimens were discovered more than 100 years ago in the limestone of the Pyrenees mountains in Spain, but their true significance was not then realized, the scientists said.
"This fossil material has been poorly understood and misinterpreted in the past," the authors wrote.
Montsechia vidalii, estimated to have lived between 130 million and 125 million years ago, grew during the Cretaceous period, when dinosaurs still walked the earth. It may not have looked much like the flowering plants of today -- in fact, it probably resembled its still-living descendants called Ceratophyllum. Known colloquially as coontails or hornworts, these water-loving plants have coarse leaves ideal for koi ponds.
Unlike modern plants with flowers, M. vidalii woiuldn't have petals or nectar-producing parts, but it did have a single seed -- a telltale characteristic of angiosperms.
"Lower Cretaceous aquatic angiosperms, such as Archaefructus and Montsechia, open the possibility that aquatic plants were locally common at a very early stage of angiosperm evolution and that aquatic habitats may have played a major role in the diversification of some early angiosperm lineages," the study authors wrote.