Illustration of the extinct snake (Najash rionegrina). This snake is an evolutionary intermediate between lizards and modern snakes. It is the first snake to be found to have a sacrum, the bone at the base of the spine that forms part of the pelvis. As well as a sacrum and pelvis it had well developed functional hind legs. N. rionegrina lived in what is now Argentia around 90 million years ago during the late Cretaceous.