School › Dinosaurs › Ages 10–11
Dinosaurs: when, what and how we know
When dinosaurs lived, what makes an animal a dinosaur, what fossils can tell us, the Bernissart Iguanodons, the asteroid that ended the age of dinosaurs, and how birds survived. With a fair-test footprint investigation.
Read
Dinosaurs lived in the Mesozoic Era, from 252 to 66 million years ago. The first dinosaurs appeared about 230 million years ago.[1][2]
What makes a dinosaur? All dinosaurs held their legs directly under the body, and their ankles bent like a hinge. Flying pterosaurs, sea reptiles and crocodiles lived at the same time, but they were not dinosaurs.[2][1]
Scientists sort dinosaurs into two big groups by the shape of their hip bones: ornithischians and saurischians. The shape of the teeth shows whether a dinosaur ate meat or plants. Most, if not all, laid eggs, and their fossils have been found on every continent, even Antarctica.[3]
In 1878, miners at Bernissart in Belgium found bones 322 metres underground: about thirty Iguanodon skeletons. Iguanodon was a plant-eater, 6 to 7 metres long, with a spike on its thumb. The skeletons were first put up standing like kangaroos, but in 1980 a scientist concluded that Iguanodon walked on all fours. New evidence can change our ideas.[7]
About 66 million years ago, an asteroid about 15 km wide hit Chicxulub in Mexico. Dust blocked the sunlight and caused a global winter, and more than half of all species on Earth died out, including the non-avian dinosaurs.[4][2]
Not all dinosaurs died out. Birds evolved from small meat-eating dinosaurs called theropods. Since 1996, many dinosaurs with feathers have been found, and Archaeopteryx, found in Germany, could glide.[5][6][1]
Our own species first evolved in Africa more than 300,000 years ago: more than 65 million years after the last non-avian dinosaurs.[8][2]
Try it: Footprint detectives: is hip height about 4 × foot length?
You need
- A tape measure or metre stick
- Chalk, or a long strip of paper and a damp sponge for wet footprints
- Calculator
- A recording table
Safety
Use a flat, dry, uncluttered space. Jog gently, do not race. Wipe up wet footprints so nobody slips.
What to do
- Scientists estimate a dinosaur's hip height as about 4 times the length of its footprint. Let's test that rule on ourselves.
- In pairs, measure each other's foot length (heel to longest toe) and hip height (floor to the top of the leg bone at the side of the hip), in cm.
- Calculate 4 × foot length. Is it close to the real hip height?
- Walk normally along the paper strip or chalk line with a damp sock or chalk on one shoe. Measure your stride: the distance between two prints of the same foot.
- Fair test: walk again, then jog gently, on the same surface. Change only the speed; keep the same person and the same shoes.
- Compare: is the stride longer when you go faster?
What happens, and why?
Palaeontologists estimate a dinosaur's size and speed from its trackway: hip height is about four times the footprint length, and the stride (two prints of the same foot) is longer when an animal moves faster for its size. The 'times 4' rule is only a rough guide.[9]
Play: Dino fact or myth?
Is each sentence true or false?
Your best score is kept only on this device. Nothing is sent anywhere.
Quiz
Other ages: Ages 6–7 · Ages 15–16