Dying to Become a Fossil 

Oreodonts were common throughout the Badlands but became extinct. Their fossil remains provide evidence of their lives and habitat. Fossils can develop over time when animal or plant remains are quickly covered in sediment and replaced by minerals. 

Ancient Life 

There are a number of different ways animals and plants can become fossils. Remains can have all, some, or none of the original materials replaced by minerals. Some fossils are impressions, casts, or molds of the remains. The basic steps are illustrated here for this oreodont fossil. 

Death and Decay  

When this animal died, its remains were quickly buried in mud, sand, or soil. Soft elements decayed quickly while hard bone or teeth remained. 

Burial 

Over time, more and more sediment covered the remains. Teeth, bones, and other parts less likely to break-up or decay were encased in the sediment. 

Change 

Eventually, the skeletal material dissolved and was replaced by minerals. This process resulted in a copy of the oreodont preserved within the rock. 

Discovery

Fossils surviving the ravages of time, particularly erosion, may be discovered by paleontologists or visitors. Hard parts, like teeth, and other parts replaced by minerals stand a better chance of discovery. Sometimes, as with this oreodont, fossils provide the only evidence of a non extinct animal.