Eurypterids: Scorpions of the Sea (PA-12)
More than 450 million years ago, a family of anthropods called eurypterids appeared in the ancient seas. They had blunt, narrow heads, tapering and segmented abdomens, and exoskeletons ornamented with knobs, scales and ridges. They were commonly 5 to 30 inches long, some were 5 or 6 feet long, and the n largest yet found was 10 feet long. They had 5 or 6 pairs of legs, four for walking and holding food and one probably for swimming.

Early eurypterids were marine, but during the Silurian Period many took up life in brackish-water lagoons. Later, many moved to swamps and rivers. They became extinct about 220 million years ago. Many specimens have been found in the Kokomo limestone in north-central Indiana.

Our Hoosier State Beneath Us: Paleontology