WHEN DINOSAURS RULED Dinosaurs were amazing animals They could be bigger than a school bus or as small as a chicken They could be mean meat eaters or gentle plant eaters Dinosaurs ruled Earth for a long time But 66 million years ago almost all dinosaurs died out So how do we know so much about dinosaurs Fossils A fossil is what is left behind when something dies A A fossil may come from a plant or animal It may come from a bone footprint or egg Fossils can tell us when how and where dinosaurs lived long ago 4
WHEN DID DINOSAURS LIVE 66.4 MILLION YEARS AGO TERTIARY LATE cretaceous 975 MILLION YEARS AGO EARLY cretaceous 144 MILLION YEARS AGO JURASSIC 208 MILLION YEARS AGO TRIASSIC THIS CHART SHOWS SOME DIFFERENT KINDS OF DINOSAURS AND THE TIME PERIODS IN WHICH THEY LIVED 245 MILLION YEARS AGO Explore More ARCHOSAURS WERE PART OF A LARGE GROUP OF REPTILES THAT INCLUDED DINOSAURS MOST ARCHOSAURS DIED OUT BUT TWO EVOLVED AND STILL LIVE TODAY BIRDS AND CROCODILES 5
A FOSSIL FORMS When a plant or animal dies its remains usually disappear They might be eaten by animals or rot in the open air But sometimes remains become covered in matter like mud sand or ice This guards remains from wind water and animals that might eat them 1 2 6 AFTER AN ANIMAL OR PLANT DIES IT MAY BE BURIED UNDER THE EARTH AND BECOME A FOSSIL
Remains are often buried in sediment This can be stone sand shell or mud from rivers and oceans Sediment surrounds the remains and slowly turns to rock This preserves the remains Over time sediment pushes down on the remains The remains turn to rock as well Now they're fossils Explore More NOT EVERY OLD BONE OR FOOTPRINT IS A FOSSIL REMAINS MUST COME FROM PLANTS OR ANIMALS THAT LIVED THOUSANDS OR MILLIONS OF YEARS AGO 3 4 cy 0238 800 SON THE ANIMAL OR PLANT REMAINS ARE PRESSED DOWN BY SEDIMENT AFTER A LONG TIME THE EARTH MAY MOVE AND RAISE THE FOSSIL UP 7
