How do dinosaur fossils form?

What are fossils? How do dinosaur fossils form? And how are they discovered?

In nature, plants and animals generally undergo complete decomposition, but under a specific set of circumstances, when an animal like a dinosaur dies, petrification can leave evidence of its existence. Natural History Museum London vertebrate paleontologist Dr David Button explains:

“Most of the dinosaur fossils we find are from animals that were living near to a lake or river.

“Some died shortly before the area flooded and covered their remains in mud and silt. Others were washed into a river by heavy rain…

“We don’t know about many dinosaurs that lived in jungle or mountain environments. Fossils are very unlikely to form in such situations.”

When the creature’s remaining bones and teeth are trapped by layer upon layer of mud, sand, or silt, the weight and pressure compress the sediment over thousands or even millions of years, creating sedimentary rock. At the same time, water seeps into the bones and teeth.

“The water leaves mineral crystals behind in spaces in the bones. This is why dinosaur fossils often have a sponge- or honeycomb-like texture: the internal bone structure has been preserved.”

As geological formations change, and wind, rain, and time erode the sedimentary rock, fossils can become exposed. Vertebrate paleontologist Professor Paul Barrett notes: “We spend a lot of time walking around, looking at the floor.”

Watch these fossil videos next on TKSST:
• Life, death, and discovery of a plesiosaur
• Mary Anning, the greatest fossilist the world ever knew
• The revealing world of dinosaur poop (coprolites)
• Petrified Forest National Park: How is petrified wood made?
• A kid discovers a 32-million-year-old fossilized nimravid skull

Bonus activity: How to make salt dough ammonite fossils.