Hi Blackmont.

Horseshoe crabs. Horseshoe crabs are often called living fossils because they have changed little in the last 445 million years.
Sharks. Evidence of the existence of sharks extends back over 450-420 million years. The modern sharks began to appear about 100 million years ago.
Turtles. They have exsisted since the Triassic, the time of the dinosaurs. The earliest turtles date back 215 million years, making turtles one of the oldest reptile groups.