We’ve seen large mammals, but what about large turtles? These extinct animals are the largest turtles to have ever existed. They weighed over 4,900 pounds, and measured around 16 feet from head to tail. That’s huge! Through evolution, modern day turtles have hard shells on their bodies, but the Archelon had a leather carapace. They existed around 100 million to 66 million years ago, during the Late Cretaceous epoch (Wikipedia).