The Hsanda Gol Formation of Mongolia represents an arid desert basin .
The environment is thought to have had few tall trees and limited brush cover , as the fauna consisted mainly of animals that fed from tree tops or close to the ground .
The Hsanda Gol Formation of Mongolia represents an arid desert basin , and the environment is thought to have had few tall trees and limited brush cover , as the fauna consisted mainly of animals that fed from tree tops or close to the ground .