Parsing the Trilobites' Rise and Fall

摘要

In Earth's first evolutionary flowering, the Cambrian explosion, the trilobites-hardy, shelled arthropods beloved of fossil hunters everywhere-were big winners, quickly filling many niches on the ocean bottom. But they seemed to miss out on the next evolutionary burst, about 475 million years ago during the Ordovician period. While mollusks, corals, and stationary filter feeders diversified rapidly and laid the foundation for today's sea-floor ecosystem, trilobites seemingly slid into a protracted decline. By 250 million years ago, they had disappeared for good.