Dinosaurs probably lived to be between 75 to 300 years of age. Scientists figured this out from looking at the structure of their bones.

One way to tell the age of a fish is by looking at its scales. They have growth rings just like trees. These are called circuli. Clusters of them are called annuli. Each annuli show one year.

The northern fur seal, rather than using a layer of fat to keep it warm, depends on its thick fur with some 300,000 hairs per square inch.