Dinilysia

Dinilysia Temporal range: Late Cretaceous,
Illustration of the skull and vertebral column
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Order:	Squamata
Clade:	Ophidia
Family:	†Dinilysiidae
Genus:	†Dinilysia Woodward, 1901
Type species
Dinilysia patagonica Woodward, 1901

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 not support the suggestion that snakes were burrowers during their ancestry; it is clear that Dinilysia was terrestrial.

Figure 1: Hypothetical appearance of Dinilysia patagonica (reconstruction based on skeletal and other features).

Physiology and Lineage

Figure 2: Bony inner ear labyrinth of the Dinilysia patagonica

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 significant, 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 sacular otolith, which transmits vibrations to the snakes brain. Due to a spherical vestibule, the Dinilysia patagonica was a species especially sensitive to low frequency ground vibrations than airborne frequencies.

The surmounting evidence displays that the 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.

References

• Caldwell, M.W. & Albino, A.A., 2002. Exceptionally preserved skeletons of the Cretaceous snake Dinilysia patagonica, Woodward, 1901. Journal of Vertebrate Paleontology 22: 861-866.
• Fossils (Smithsonian Handbooks) by David Ward
• Dinosaurus: The Complete Guide to Dinosaurs by Steve Parker. Pg. 99
• Fossil Snakes of North America: Origin, Evolution, Distribution, Paleoecology (Life of the Past) by J. Alan Holman