Tuatara
Tuatara at first glance look like a lizard but they have many unique qualities that make them a completely different group. They have a very primitive body structure and are believed to not of changed much in the past 220 million years. They have loose skin and are only found in New Zealand.
Tuatara posses many differences from lizards. They have bony processes on their ribs, extra holes in their skulls and males do not have copulatory organs. Tuatara have a third eye also known as parietal or pineal eye. This third eye has a basic lens and retina. The eye is covered with opaque scales which probably makes the formation of an image impossible. Many scientists believe that this third eye acts as a photo sensor and lets the tuatara know when it has spent enough time basking.
Tuatara also have unusual teeth. Their teeth are more like serrations on the jaw bones and are not replaces when broken or wore down. There is a single row of teeth on the bottom jaw and a double row on the top jaw. When the tuatara closes its jaws the lower teeth fit between the two rows of upper teeth.