Image: Courtesy DAVID DILCHER and GE SUN

Scientists have discovered in China the oldest, most complete flowering plant fossil yet, according to a new report. The 125-million-year-old specimen belongs to a new plant family and provides clues as to how now extinct species gave rise to modern flowering plants, or angiosperms. The work, published today in the journal Science, suggests that angiosperms--the dominant vegetation in the world today--may have evolved from aquatic, weedy herbs.

Ge Sun of Jilin University in China and his colleagues recovered the complete fossil of the plant, dubbed Archaefructus sinensis, from a slab of rock found in northeastern China's Liaoning Province by local farmers (see image). The region, which has produced an array of remarkable fossils, yielded a similar but incomplete fossil in 1998. "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," says study co-author David L. Dilcher of the University of Florida. Although the plants lacked flowers, the scientists discovered evidence of seeds enclosed within the female reproductive organs, a characteristic of flowering plants. With its thin, curving stems, A. sinensis had a vaguely seaweed-like appearance.

To determine how their find fits into the evolutionary family tree, the researchers compared the traits evident in the fossil plant with genetic and morphological information from 173 modern flowering plants. The results indicate that the specimen represents a previously unknown family, Archaefructaceae, with two species A. liaoningensis and A. sinensis. The authors propose that Archaefructaceae is a sister group to all exant angiosperms. Further research is needed before Archaefructus is fully accepted as the most ancient flowering plant known, but botanists are excited about its implications. "The mysteries of the origin and radiation of the flowering plants remain among the greatest dilemmas facing paleontology and evolutionary biology," says plant biologist William L. Crepet of Cornell University. He adds that the new fossil is "one of, if not the most, important fossil flowering plant ever reported."