Certain characteristics of bones help to identify the family of animal that they originated from. Bird bones, like this bone from a swan that lived at Hagerman Fossil Beds National Monument about 3 million years ago, are hollow, and are easily differentiated from mammal bones, based on this characteristic. Also, different types of bones yield more information than others. By examining a leg bone and using comparative anatomy and physics, a paleontologist can learn about adaptations the animal had for digging, running, climbing, or catching prey, for examples. However, rib bones would only give clues to the general shape of the animal's torso.