Cobelodus is an extinct genus of shark that lived in the Middle to Late Carboniferous Period in what is today Illinois and Iowa. Cobelodus was a two-meter long predator of Carboniferous oceans. Although it was a shark, Cobelodus did not exactly resemble one. It had a bulbous head, large eyes, a high-arched back and a dorsal fin placed far to the rear, above the pelvic fins. Because of its large eyes it is thought to have lived in the deeper, darker parts of the sea, hunting crustaceans and squid. Another mysterious physical feature of Cobelodus are the 1 ft (30 cm) long, flexible cartilage 'tentacles' sprouting from its pectoral fins. Their purpose is unknown.