Millions of years ago,
this dinosaur was going about his normal daily life.
But his day went from good to bad.
After he died, other dinosaurs ate him.
And the rest of his skin and muscles rotted away,
leaving just his bones.
These were quickly buried by mud.
Over millions of years,
more layers landed on top
mud, sand and even volcanic ash.
This added up to a lot of weight on top of the skeleton.
Some parts got crushed.
The layers of mud, sand and ash
turned into hard sedimentary rocks.
While this was happening, water seeped into the bones.
It left behind minerals,
turning the bones to stone and creating a fossil.
Earth changed a lot over millions of years.
Rocks that were once deep underground rose to the surface,
a process called uplift.
Very slowly, wind, water and ice
wore away the rock.
Eventually,bits of the fossil skeleton were exposed
and became visible on the surface.
Fossils are constantly getting eroded out of rock.
Most are lost.
But if we’re very lucky, someone will find one.
Nearly all of the fossils we find
around 99 % are from marine animals,
such as shellfish and sharks.
This is because they lived in the sea,
where sand or mud
could bury their remains quickly after they died.
But dinosaurs live on land,
so how do they get buried so quickly?
Most dinosaur fossils we find belong to animals
that were living near to a lake or a river.
They died and a short while later the area flooded,
covering their remains in mud and silt.
Occasionally, something more dramatic happened.
In one example, two dinosaurs –
Protoceratops and Velociraptor –
were fighting in the desert.
They were mid-battle
when, suddenly, a sand dune collapsed on top of them.
Their fossils show them frozen in their fighting poses.
In another tragic example,
the feathered dinosaur Citipati was sitting on its nest of eggs
when a sandstorm blew in and covered it.
Fossils like this
from animals that were alive when they were buried –
are really rare.
It’s not just bones that turn into fossils.
Dinosaurs can also leave behind footprints
and impressions of skin and feathers.
So next time you’re near some sandstone or mudstone,
think of what fossils could be hiding,
just waiting to be discovered.
It probably won’t be a dinosaur fossil,
as they’re so rare.
But it could be a prehistoric sea creature
like an ammonite,
which went extinct at the same time as dinosaurs,
many millions of years ago.
Millions of years ago,