The first snakes are believed to have been burrowing animals, similar to modern-day blind snakes. They likely had small eyes and a blunt head, and their bodies were covered in small, overlapping scales. Their teeth were likely conical in shape, and their diet probably consisted of small invertebrates, such as worms and insects.

As snakes evolved, they began to develop longer bodies, and their limbs eventually disappeared. Their skulls also became more complex, with the development of larger eyes, a hinged jaw, and specialized teeth for catching and eating prey.

The first snakes are thought to have appeared during the Cretaceous period, around 145 million years ago. They were likely descended from a group of lizards called mosasaurs, which were aquatic animals that lived in the oceans. Over time, some of these mosasaurs moved onto land and eventually evolved into snakes.