Dinilysia (meaning "terrible ilysia") is an extinct genus of snake from the Late Cretaceous (Coniacian) of South America. 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 does support the suggestion that snakes were burrowers during their ancestry; it is clear that Dinilysia was terrestrial.
Dinilysia never appeared in the Jurassic Park novels or movies.
It has however appeared in Jurassic Park III: Park Builder. Strangely, it looks nothing like a snake once it is placed in the actual park. It comes from the family Diniysiidae, which is not listed in the game, oddly.