Labels:text | screenshot | font OCR: ORDOVICIAN PERIOD 505-438 MYA Mollusks (soft-bodied animals without a backbone, protected by a hard shell), such as nautiloids, inhabited the seas. Trilobites, with coiled shells, teemed in the waters. Bivalves (mollusks with a two-part shell) lived near the shoreline. Corals formed reefs, and the first vertebrates (animals with a backbone) evolved as jawless fish.
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