Dinilysia (meaning "Terrible Ilysia") is an extinct genus of snake that originated during the Late Cretaceous period in North and South America and was also some of the earliest, if not, the earliest known snakes. The snake reached a length of 6-10 feet (1.8-3 meters) and preyed on smaller animals. The shape of the animal's skull doesn't support the suggestion that snakes were burrowers during their ancestry; it is clear that Dinilysia was terrestrial.
Dinilysia measured 6-10 feet long, which was large for a primitive snake. As a species of Late Cretaceous snake, during the Late Cretaceous, these reptiles had only recently evolved from the same family as lizards, but by then, the specialized in hunting warm-blooded creatures such as mammals. To do this, they used special sensory pits on their snouts as a way of detecting the heat signatures of other animals.