The birds of today sing or whistle or screech. But the first birds may have hissed like snakes! They were more like reptiles than like birds. They were reptiles with wings and feathers. The first...
Flying reptiles
No reptile that lives today---snake, turtle, lizard, alligator, or crocodile---can fly. And no reptile of today has hair on its body. But scientists say that 150 million years ago there were many...
The biggest dinosaurs
You could have walked beneath an Apatosaurus and your head wouldn't even have touched its stomach. An Apatosaurus was as long as four big elephants standing in a line. The word Apatosaurus means...
Turtles and terrible lizards
According to most scientists, the first dinosaurs came into the world about 225 million years ago. And along with them came the first turtles. The word dinosaur means terrible lizard. But the first...
A 250-million-year-old puzzle
Scientists tell us that about 250 million years ago there lived a big reptile called Dimetrodon. It was about as long as a small automobile. It ate smaller reptiles. Dimetrodon had a big fin like a...
The first four-footed animal
Imagine a fish with legs! Once upon a time, there really was an animal that looked like a fish with legs. Most scientists believe that about 400 million years ago it swam in the warm, green waters...
Fish in armor
According to most scientists, the fishes that swam in the seas 430 million years ago were covered with hard, bony armor. They had no jaws like the fish of today. Their mouths were just holes in the...
Strange sea animals
Scientists say that five hundred million years ago all plants and animals lived in the sea. There were sponges, jellyfish, worms with legs, and things like clams. And there was another animal that...
Animals of Long Ago
Imagine animals like fish with legs. Imagine trees like giant feather dusters. That's what some animals and trees looked like, once. Just as you change as you grow older, the world changes and the...
Change or die!
Eohippus Scientists think the eohippus was the ancestor of the modern horse. The eohippus was a small animal that had toes instead of hoofs. Suppose that all the milkweed plants in the world...