Animals having a spinal column, including fish, reptiles and birds. Fossils are generally limited to skeletal remains but sometimes also include cartilage, skin, scales and stomach contents. My list of fish refererences are here .
Sharks are an old family of fish, dating back many millions of years to the Devonian Period.
They were common predators and scavengers in the Western Interior Sea. Sharks shed their teeth continuously through their life and these isolated teeth are frequently found in the chalk. Tthese creatures grew to 15 feet or more in length and were one of the top predators in the Western Interior Sea. Their triangular, blade like teeth are the largest found in the chalk and their thin, disk shaped vertebrae are also found . Sometimes the entire shark including skin is preserved as a fossil.