Dinilysia (meaning "terrible ilysia") is an extinct genus of snake from the Late Cretaceous (Coniacian) of South America. Dinilysia was a relatively large ambush predator, measuring approximately long. The skull morphology of Dinilysia is similar to boids, suggesting that it was able to consume large prey. Living in a desert-like environment, Dinilysia is likely a terrestrial or a semi-fossorial animal. Physiology and Lineage The Dinilysia patagonica is a stem snake that is very closely related to the original ancestor of the clade of crown snakes. Once the fossil of the snake was discovered, an x-ray computed tomography was used to build a digitized endocast of its inner ear. The results displayed that the Dinilysia patagonica's inner ear anatomy had 3 main parts. It had a large spherical vestibule, large foramen ovale, and slender semicircular canals in its inner ear. Especially significantly, the spherical vestibule is an inner ear organ that is a morphological signature of burrowing snakes. A large spherical vestibule does not exist in aquatic or generalist (both land and water) snakes, only in snake species that burrow. A spherical vestibule contains a large saccular otolith, which transmits vibrations to the snake's brain. Due to a spherical vestibule, the Dinilysia patagonica was a species especially sensitive to low-frequency ground vibrations rather than airborne frequencies. The surmounting evidence displays that Dinilysia patagonica was more than likely a terrestrial burrower from the Cretaceous era. This discovery also extends its evidence to the fact that a burrowing habit predates the lineages of modern snakes. These ancestral snakes detected predators and captured prey specifically using low-frequency ground vibrations. Theories of Origin Dinilysia patagonica is one of the best known Cretaceous, terrestrial-snakes, native to the Late Cretaceous Anacleto Formation of Neuquen province, Argentina. The Dinilysia specimen has twenty-four mid-posterior trunk vertebrates. Dinilysia is referred to as such due to a variety of morphological features. The degree of knowledge represents the most valuable records of snakes from the Upper Cretaceous of Gondwana. Recently, Dinilysia has been labeled a sister group of all living alethinophidia. Therefore this Crataceous snake still contributes a significant amount within the debate on the origin of snakes and phylogeny. In terms of the locality and age of the Dinilysia the fossils can typically be found in abundance in sandstone sediments favored to the Anacleto formation. Additionally, the overall morphological similarities between that of D. patagonica has been used to determine the