SAN FRANCISCO, Feb. 15 -- Researchers have found the first-ever fossil specimens of a family of flowering plants that gave us everything from the potato to tomatoes, tobacco, petunias and morning cup of coffee.

The discovery of two fossil flowers, age 20-30 million years, of the asterid family, in the prehistoric jungles of what is now the Dominican Republic was announced Monday in the journal Nature Plants.

George Poinar, Jr., a courtesy professor in the College of Science at Oregon State University, said "the specimens are beautiful, perfectly preserved fossil flowers, which at one point in time were borne by plants that lived in a steamy tropical forest with both large and small trees, climbing vines, palms, grasses and other vegetation."

"Specimens such as this are what give us insights into the ecology of ecosystems in the distant past," Poinar said. "It shows that the asterids, which later gave humans all types of foods and other products, were already evolving many millions of years ago."

Asterids, researchers noted, are among Earth's most important and diverse plants, with 10 orders, 98 families, and about 80,000 species. They represent about one-third of all the Earth's diversity of angiosperms, or flowering plants.

However, researchers said the fossil flowers came from the dark side of the asterid family, as they belong to the genus Strychnos, which ultimately gave rise to some of the world's most famous poisons, including strychnine and curare.

Inherently toxic, the genus existed for millions of years before humans appeared on the planet.

"Species of the genus Strychnos are almost all toxic in some way," said Poinar, one of the world's experts on plant and animal life forms preserved in amber. "Each plant has its own alkaloids with varying effects. Some are more toxic than others, and it may be that they were successful because their poisons offered some defense against herbivores."

"Today some of these toxins have been shown to possess useful and even medicinal properties."

There are now about 200 species of Strychnos plants around the world, in forms ranging from shrubs to trees and woody climbing vines, mostly in the tropics. They are being studied for medicinal properties, such as for the treatment of parasitic worm infections and as drugs to treat malaria.

The discovery of the fossil flowers, researchers said, suggests that many other related plant families could have evolved in the Late Cretaceous in tropical forests. Their fossil remains, awaiting discovery.