What Is A Fossil?

fossil…

The word brings up visions of giant dinosaurs or ancient sea creatures.  

So, what is a fossil, anyway?                  

The short answer is that a fossil is the remains or evidence of any living thing that once lived on the earth. 

That simple definition doesn’t really give us the whole picture. We can group the many different types of fossils into just two categories.

Scientists look at how the fossil relates to the original organism.  A Type I fossil is any actual remains of the original organism or an imprint made by the actual remains. Type II is called a trace fossil. It is something made by the original animal. A Type II fossil does not contain any actual remains of the original organism

Type I fossils include bones, teeth, skin imprints, hard shells of animals with no backbone, or the impression of the organism left in stone even when the actual body parts no longer remain.

There are many ways that body parts can be preserved as a fossil. Freezing, drying, caught in sap that hardens over time, petrification, and carbonization are the main paths to fossilization. When an animal freezes, even the hair can be preserved and be considered a fossil.

Type I can also be molds or casts of the original organism. When the body decayed it might have left an imprint or an empty space.  This sort of fossil is called an exterior mold or simply a mold. If the space in the body structure is first filled with minerals and then the original animal or plant part dissolves, it is called a cast.  

Type II fossils are called trace fossils. They are not the plant or animal remains but signs that show that a living thing passed over the land when it was alive. Type II fossils can be footprints, burrows, tooth marks, or even poop (coprolite). Like the Type I fossils, Type II can be molds or casts.

So, what is a fossil? A fossil can be many things: a cast, a mold, a trace of something the organism left behind. It can be a track made in soft mud or hardened dung. It can be turned to stone by minerals in the water where the organism died. It