Page "Dinotopia" Paragraph 11

The caverns are referred to as the World Beneath, and many dinosaurs go there to die.

According to legends, a half man-half ceratopsian being named Ogthar climbed down there ( where the sun is said to sleep at night ) and stole pieces of it ( known as " sunstones "), using them to create the empire of Poseidos and populating it with metal dinosaurs.

However, the sea grew angry with the artificial city and rose to destroy it.

It is implied that this is where the Atlantis myth originated.