A mushroom found embedded in a 100-million-year-old piece of amber is about 20 million years older than other known mushroom fossils, an Oregon scientist says.

The ancient mushroom is especially interesting because it contains two parasites, one feeding on the mushroom and the other feeding on its fellow parasite.

"I was amazed enough with the mushroom," said George Poinar, a retired entomology professor in Corvallis. "But then seeing the parasites was astonishing. No one has ever seen this three-tier association before."

Poinar, formerly of the University of California at Berkeley, said the mushroom was spotted about a year ago in Burma by Ron Buckley, a registered nurse, photographer and collector of amber fossils from Florence, Ky.