The fossil, discovered in 2010 in sediment among the cliffs above La Estafeta beach in the lower part of the Playa Los Lobos Allo Formation of around 3.5 million years ago to the Late Pliocene.

[2] CT scans of its inner ear show that it could only hear frequencies between about 380 and 4230 hertz, and probably had a deep voice to match.

[3] These same CT scans also show that the inner ear of Llallawavis is fine tuned to sudden changes in movement, likely from quickly turning when trying to catch prey.

This is corroborated by studies of a close relative of Llallawavis, the larger Mesembriornis, whose limb bones have been found to show various adaptations towards high-speed pursuit of prey, with estimates suggesting a top speed of 27 m/s (97 km/h; 60 mph),[4] though somewhat slower speeds have been suggested as more plausible.

Combined, this paints mesembriornithines such as Llallawavis as high-speed pursuit predators chasing small notoungulates across open plains in a manner similar to that of a cheetah, in contrast with their much larger, more robust phorusrhacines (ambush predators of more wooded areas that hunted the larger notoungulates, glyptodonts, and ground sloths).