Ammonites are perhaps the most widely known fossil, possessing the typically ribbed spiral-form shell as pictured above. These creatures lived in the sea between 240 - 65 million years ago, they became extinct along with the dinosaurs. The name 'ammonite' (usually lower-case) originates from the Greek Ram-horned god called Ammon.
Megalodon was not only the biggest shark in the world, but one of the largest fish ever to exist. Estimates suggest it grew to between 15 and 18 metres in length, three times longer than the largest recorded great white shark.
Without a complete Megalodon skeleton, these figures are based on the size of the animal's teeth, which can reach 18 centimetres long. In fact, the word Megalodon simply means 'large tooth'.
Trilobites are arthropods, think of them as crab like animals, not bugs! They are a very diverse Class of animal. Trilobites were among the most successful of all early animals, existing in oceans for almost 300 million years.