Turtles are strange-looking creatures. The shells on their backs are like roofs that they carry with them wherever they go. No other animals in the world have shells quite like these. The shell has been the secret of the turtle’s success for millions of years.

Like dinosaurs, turtles are primitive reptiles that first appeared on earth about 200 million years ago. These early turtles had smaller shells than most modern turtles. The small shells left the turtles’ heads exposed. As dangerous predators began to appear, many turtles gradually developed larger shells that allowed their heads to fit inside.

Today, dinosaurs no longer roam the earth. But turtles keep plodding along, mostly unchanged over the years. Their shells give them excellent protection, and this has helped them adapt to all but the coldest parts of the world. They live in jungles, mountains, rivers, deserts, and in the sea.

There are more than 200 different species of turtles in the world. They range in size from tiny speckled tortoises, which weigh less than one-half pound, to monstrous leatherback turtles, which can weigh 1,500 pounds! Most of these species fit into one of three main groups—freshwater turtles, sea turtles, or tortoises. Be sure to check out Zoobooks Turtles to learn even more fun facts about turtles!