Fossil Facts



  • Fossils are the remains of living things preserved for millions of years, usually in stone.
  • Most fossils are the remains of living things such as bones, shells, eggs, leaves and seeds.
  • Trace fossils are fossils of signs left behind by creatures, such as footprints and scratch marks.
  • Paleontologists (scientists who study fossils) tell the age of a fossil from the rock layer in which it is found. Also, they measure how the rock has changed radioactively since it was formed (radiocarbon dating).
  • The oldest fossils are called stromatolites. They are fossils of big, pizza-like colonies of microscopic bacteria over 3500 million years old.
  • Scientists study fossils to learn about the Earth’s history and about the animals and plants that lived millions of years ago.
  • When an animal dies, its soft parts rot away quickly. If its bones or shell are buried quickly in mud, they may turn to stone. When a shellfish such as this ancient trilobite dies and sinks to the sea-bed, its shell is buried. Over millions of years, water trickling through the mud may dissolve the shell, but minerals in the water fill its place to make a perfect cast.
  • The biggest fossils are conyphytons, 2000-million-year-old stromatolites over 100 m high.
  • Not all fossils are stone. Mammoths have been preserved by being frozen in the permafrost (see cold landscapes) of Siberia.
  • Insects have been preserved in amber, the solidified sap of ancient trees.
  • Certain widespread, short-lived fossils are very useful for dating rock layers. These are known as index fossils.
  • Index fossils include ancient shellfish such as trilobites, graptolites, crinoids, belemnites, ammonites and brachiopods.