Which of these animals is NOT a lizard?

The Tuatara is not a lizard because it belongs to a completely separate group of reptiles called the Rhynchocephalia. While they may share some physical similarities with lizards, such as a scaly skin and a similar body shape, Tuataras have distinct features that set them apart. They have a unique dentition, with two rows of teeth in the upper jaw and one row in the lower jaw that is fused to their skull. Additionally, Tuataras have a "third eye" called the parietal eye on top of their heads, which is a light-sensitive organ that helps regulate their daily and seasonal activities. These distinguishing characteristics clearly differentiate the Tuatara from lizards, making it a unique reptile species.