This coiled shell from Winneshiek County was inhabited by a snail.
The sluggish, bottom-dwelling mollusk scavenged or grazed the ancient sea floor about 440 million years ago (Ordovician).
Distinctive colonial forms from eastern Iowa include the “chain coral” (left), Pachyphyllum (middle), and Lithostrotionella (right).
They were especially abundant in Devonian and Silurian seas, 375 to 425 million years ago.
This Floyd County specimen, with its prominent nodes, lived 370 million years ago (Devonian) These shells are among the most common fossils found in Iowa.
Brachiopods lived inside the protective cover of two hinged shells, attached to the floor of warm, shallow seas that once covered the state.
These squid-like animals lived in chambered shells and could propel themselves by ejecting water from a tube near their head.