Dizygocrinus montgomeryensis crinoid fossil found in Iowa.  This creatured lived in the Carboniferous Period (345-280 million years ago)....

Halysites catenulatus of the Silurian Period found in Kentucky.  Fossil displayed at Smithsonian Museum on Natural History (August 2010)....

Phacops rana (Green, 1832) trilobite fossil found in Ohio.  Animal existed during the Devonian Period.  Fossil on display at Smithsonian ...