Cladoselache
The Cladoselache were living in the ocean during the Denovian period more than 400 million years ago. This species was known as one of the oldest known sharks with a nearly fully preserved fossil. It swam in the oceans of what is now considered North America.
This shark is considered by scientists to be the first “true” shark. The sharks were covered in scales and had a small patch along the edges of their fins. They were about 5.9 feet long, and they had little mouths and smooth-edged teeth suited for grasping, tearing, and chewing.