Psittacosaurus gobiensis was about three feet long, lived during the Cretaceous Era, and was very much like a modern parrot in features and behavior. It is considered a parrot on steroids. This genus discovered nut eating about 60 million years before the existence of the first parrots.
This photograph depicts the skull of a Macaw next to a skull of a discovered dinosaur, Psittacosaurus gobiensis.
The remains of the species were found in the Gobi Desert in Mongolia in 1922 and the remains were the earliest and most complete species of dinosaur found around the time the remains were discovered in that area.
The skull provides evidence that the species had reinforcements and powerful muscles in its jaws, similar to modern parrots. Abrasions on the teeth provide evidence that this species chewed food by sliding the lower jaw forward and then drawing it up and back against the upper teeth. This is different from most reptiles who simply keep their jaws shut or slide them back and forth in order to grind up food. In addition, stones were found used to break down hard foods like nuts, seeds and nutshells and many of today's birds, including parrots, use stones in aid of digestion.
It's believed that this dinosaur was a plant eating species and lived in an environment with a large amount of plant life for food sources. In additon, these dinosaurs have only been found in areas of central Asia, and it is believed that they only survived for ten to twenty million years.
Source: http://dsc.discovery.com/news/2009/06/1 ... -dino.html