Mathews and Donoghue published their results first, in the Oct. 29 issue of the U.S. journal Science . Two other teams published their findings in the Nov. 25 issue of the British journal Nature . Despite these new findings, plenty of mysteries remain. None of the analyses reveals when the first flowering plant appeared on Earth. Sometime before 140 million years ago, flowering plants, known as angiosperms, diverged from nonflowering seed plants known as gymnosperms.
Biologists imagine a tree of life with different groups of animals or plants as branches.
Flowering plants branched off from within the branch of seed plants. Fossils of gymnosperms, such as pine trees and other evergreens, go back at least 350 million years, when cockroaches as big as house cats and dragonflies with the wingspans of modern hawks prowled the planet. Therefore, the birth of flowering plants could have occurred anytime between 140 million and 350 million years ago. Another mystery involves how flowering plants were able to diversify so much and spread so rapidly. The key, they believe, lies in newly evolved structures not available to nonflowering plants.