UF Expert: Ancient Fossil Suggests Flowers May Be Underwater Gift

May 2, 2002

GAINESVILLE, Fla. — The world’s oldest known flower never bloomed, but it has opened scientific questioning into whether all of today’s flowering plants had their origins from beneath ancient waters, says a University of Florida researcher.

The newly discovered remains of the oldest, most complete flowering plant show it lived at least 125 million years ago and likely was an underwater plant, said David Dilcher, a UF paleobotanist who studied the flower. The discovery is reported in Friday’s issue of the journal Science.

Although it had no petals, there is no question it was a flowering plant because of the presence of seeds enclosed in an immature fruit, a trait separating flowering plants from all other seed plants, he said.

The discovery is important because it provides clues about how these now-extinct ancestors evolved into modern living flowering plants, said Dilcher, whose research is supported by a grant from the National Science Foundation.

“Flowering plants are the dominant vegetation in the world today,” he said. “They’re the basic food crop and fiber source for the world’s population. It’s useful for us to understand the relationships among flowering plants, especially in this day of molecular genetic manipulations.

“When you sit down in the morning and have a bowl of Wheaties or cornflakes, that’s a flowering plant,” he said. “When you eat a beef steak, that’s from an animal that ate flowering plants. So, when we study this fossil, we’re looking at the ancestry of what sustains us in the world today.”

The plant was about 20 inches high with thin stems stretching up in the water to the surface with its pollen and seed organs extending above the water, Dilcher said.

The seeds probably dispersed in the water and floated up along the shore and germinated in shallow water, he said.

“The mysteries of the origin and radiation of the flowering plants remain among the greatest dilemmas facing paleontology and evolutionary biology,” said William L. Crepet, professor and chair of the department of plant biology at Cornell University. “This fossil represents the first evidence of an angiosperm that is basal to all other angiosperms, yet that does not fit within any modern taxonomic group of angiosperms – this makes it one of, if not the most important fossil flowering plant ever reported.”

The fossil was found in China by local farmers who gave it to one of the paper’s coauthors. It is much more complete than one found at a nearby site four years ago, which Dilcher also studied, and suggests origins in water that refreshed the dinosaurs, said Dilcher, a graduate research professor at the Florida Museum of Natural History on the UF campus.

“After having only a fragment and trying to imagine what the whole plant was like, it was a great surprise to find leaves typical of a plant that lived underwater with characteristics very unique to flowering plants at such an early age in their history,” he said.

What distinguishes the fossil as an aquatic plant are its dissected leaves, Dilcher said. Some of the leaves at the base are quite branched, typical of underwater plants. This raises the question of whether flowering plant evolution happened on water or on land, he said.

Further proof of the flower’s watery existence comes in the form of fish fossils found together mixed in with the fossil plants, he said.

The compressed plants embedded in a sandy-colored slab collected from northeast China and studied at UF are at least 125 million years old and make up an entirely new plant family, he said.

Dilcher, along with Ge Sun, a geologist at Jilin University in Changchun, China, and other researchers propose Archaefructaceae as the new basal angiosperm family for this ancient specimen.

“These are the earliest most complete remains of flowering plants yet discovered,” Dilcher said. “What’s spectacular about these fossils is that all parts of the plant are present, including the roots, leaves and reproductive organs. There’s been some debate about whether the first flowering plants were woody or herbaceous. Now we see that they were herbaceous.”

Four years ago, Dilcher and his colleagues identified another species of the plant, unearthed from a nearby site, but it had only the immature fruits and stamens preserved, leaving Dilcher and Sun to guess what the rest of the plant looked like.

The plant, found in a fossil-rich section of the Yixian Formation northeast of Beijing, probably lived in a shallow lake alongside dinosaurs, crocodiles, turtles and many species of fish during the Lower Cretaceous period and possibly as early as the Upper Jurassic period, Dilcher said. The climate was warm and temperate, and scientists know that volcanoes dotted the landscape because the specimen was found in layers of ash beds.