The story opens as Big Al hatches from an egg buried in a nest chamber underground. The nest of a dinosaur very like Allosaurus has been found near Lourinha, Portugal. There were about 100 eggs in the nest and there may have been many more. Inside some of the eggs were tiny fossilised embryos that revealed the type of dinosaur that laid them. Eggshells have tiny pores to let the embryos inside breathe. Eggs which are buried underground have bigger pores than those incubated above ground. By examining the pores on the eggs in Portugal, we could tell that the nest had originally been underground
75 million years ago the Mongolian desert was home to dinosaurs of all shapes and sizes - including one with the largest claw of all time.
Argentinosaurus was the largest dinosaur ever - 35 metres long, and up to a hundred tonnes in weight.
Why the dinosaurs died out is one of the most frequently asked questions of dinosaur experts. Will we ever know the answer?
While dinosaurs dominated the land, huge marine reptiles ruled the water. Ichthyosaurs looked very like dolphins - but they weren't the top predators of the Jurassic seas.
In the Early Jurassic, dinosaurs started getting larger. Diplodocus was over 30 metres long - but even he wasn't safe from predators
The largest animals ever to fly were pterosaurs. But during their reign, birds as we know them were also beginning to appear.
When dinosaurs first appeared the world was very different. There were no mammals, no birds and no lizards. But there were some lizard-like reptiles.
There's considerable evidence that dinosaurs once lived at polar latitudes. How did they survive the cold?
It's 3.5 million years ago and in East Africa a remarkable species of ape roams the land. Australopithecus afarensis has taken the first tentative steps towards humanity by standing and walking on two legs. Just a few million years previously, Africa was covered, almost edge-to-edge, with dense rain forest. Our ancestors almost certainly used all four limbs to move and live and hunt in their tree-top homes. But massive geological turmoil changed their destiny
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