Research NewsPaleontology

Parsing the Trilobites' Rise and Fall

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Science  19 Jun 1998:
Vol. 280, Issue 5371, pp. 1837-1838
DOI: 10.1126/science.280.5371.1837a

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Robert Irion After quickly filling many niches on the ocean bottom in the Earth's first evolutionary flowering during the Cambrian explosion, the trilobites--hardy, shelled arthropods--seemingly slid into a protracted decline and by 250 million years ago had disappeared for good. Now, on page 1922 of this issue, paleontologists report a detailed new survey in which they show that while one group, or fauna, of trilobites faded precipitously during the Ordovician period, the other thrived. A still-mysterious combination of ecology, geographic distribution, and high rates of speciation evidently gave this fauna an evolutionary edge.