Hybodont Sharks

Freshwater sharks lived in coastal environments throughout North America during the Jurassic and Cretaceous periods. These were small sharks, between 3 and 7 feet long. Since shark skeletons are primarily made up of soft cartilage, most of their bodies are very unlikely to fossilize. At Dinosaur Park, tiny hybodont shark teeth are occasionally found, as well as coprolites (fossilized dung) that probably came from a shark.
Hybodont Shark Fossil