Scientists find a fossil (Fossil A) in a deep layer of sedimentary rock. They determine that Fossil A is the remains of a species never seen before. A few years later, other scientists discover a similar fossil (Fossil B) in a layer of sedimentary rock closer to Earth’s surface. Fossil A and Fossil B share some characteristics, but it is determined that Fossil A is a different species. One hundred years later, scientists discover another similar fossil (Fossil C) in a layer of sedimentary rock between those in which Fossils A and B were found. Upon examining all three fossils, scientists reach the conclusion that all three fossils represent related species.