From Halopedia, the Halo wiki
A saurio is a flat-bodied, arm-length reptile native to Gao, a human Outer Colony. The species often dwells in the planet's caverns, such as the Montero Cave System. Although they were not particularly dangerous, irritated saurios are considered to be the most hostile animal within the Montero Cave System. The reptiles share their environments with frilled salamanders and glowfish.
Having a ribbon-like pattern on their scales, saurios have webbed wings and move across the ground in a wavelike motion. When threatened, the reptiles make shrieking noises and riffled their wings in an attempt to frighten their threats. Saurios often travel in large groups. Saurios produced guano that is often found caked to the walls of their habitats.
List of appearances