Yesterday I got a fossil of a Perisphinctes, it camefrom Madagascar and it is 150 million years old. It is from the Jurassic period. It lived in the centre of the shell and when it got old it moved to the next column. Then the old columns got filled up with gas. When it died it turned into a fossil and all the gas turned to crystal.
I drew a picture of what it would have looked like if it was alive