Evidence
The evolution of the turtle species is basic from when the turtle developed out of the water in early history it hasn’t changed much. The alligator snapping turtle is one of the oddest turtle species for that reason it is called the prehistoric turtle. It has it’s differences but most turtles look the same beside the alligator snapping turtle having ridges on its shell, sharper claws and jaws, and a worm like thing on the bottom of the jaw along with some other physical changes this turtle species is very similar to any other. It is said that the first turtle species was the Odontochelys which is said to happen around the late Triassic (220 million years ago). You can see the differences and similarities of the alligator snapping turtle and the Odontochelys the first turtle.
How do we know?
We know because of modern science and fossils. I used a website that talks about turtle evolution the people who wrote the article used bones and computer programming to make an idea of what the odontochelys turtle looked liked. I also used the phylogenetic tree I found and how it has some pictures of each modern type of turtle. It also used genes as well and the DNA of the types of modern day turtles are very similar which means they are closely related.