Westlothiana
Westlothiana lived during the Carboniferous Period, about 350 million years ago, in Europe. It measured 1 foot (30 centimeters) in length. It was discovered in 1988, and named after the Westlothian district of Scotland where it was found, Westlothiana lizziae had a mixture of early tetrapod and early reptile features. Westlothiana probably lived close to fresh water lakes, hunting for small prey. It can be one of the oldest reptiles ever discovered.
There is some debate between experts in that they believe that Westlothiana is not a true reptile at all. They say that it is still more like an amphibian. For this reason it is known as a "reptiliomorph" - a form of reptile from which true reptiles evolved.