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A slab of fossiliferous, Late Ordovician limestone from the Cincinnati, Ohio, region. Many of the shelly brachipod fossils on this slab belong to species that invaded the Cincinnati region during the Richmondian Invasion--an episode of intense invasion preserved in the Late Ordovician strata of the Cincinnati region.
A study by researchers at Ohio University took a closer look at a dramatic ecological shift captured in the fossil record during the Ordovician period, about 450 million years ago. They found that major geological developments triggered evolutionary changes in the ancient seas, which were dominated by organisms such as brachiopods, corals, trilobites and crinoids.Image credit: Alycia L. Stigall, Ohio University
