Around 450 million years ago, an arthropod was buried alive. Now, scientists have uncovered its fossil preserved in a material […] ...

Using the principle of faunal succession, if an unidentified fossil is found in the same rock layer as an index fossil, the two species must have existed during the same period of time (Figure 4).

Unaltered hard parts - The body fossil is made up of exactly the same material as when it entered the rock record. Teeth are a good example as they are the hardest part in a vertebrate body, and they ...

Because so little fossil ... the iron supply is exhausted, however, oxygen begins escaping the seas into the open air. Evidence of a buildup of atmospheric oxygen first appears in rock layers ...