What are fossils?
When a plant or animal dies, it may become buried and preserved. Its organic matter is then replaced by minerals and turns into stone. But a fossil can also be anything that is dead and not decayed – perhaps it has been mummified, frozen or dried out. Fossils can be millions of years old, or more recent.
Why are they important?
Fossils can tell us how old rocks are and where there may be oil and gas. They are a record of ancient climate and other environmental conditions, and show us species that may be extinct or have evolved into other forms.
The Paleozoic era occurred 542–251 million years ago. The oldest fossils found in New Zealand are from this time, when life on earth was restricted to the sea. Near Nelson, a 14-year-old boy found the oldest fossils from this era. Fossils from this time include sponges and creatures called trilobites.
This is the age of the dinosaurs (251–65 million years ago). About 85 million years ago the New Zealand continent broke away from Gondwana, carrying with it a number of plants and animals. Fragments of fossilised dinosaur bones have been found, showing that they lived in New Zealand. Other fossils found in New Zealand include rare sharks, shells, fish and sea reptiles.
In the Cenozoic period (the last 65 million years) the dinosaurs died out and were replaced by mammals. No fossils of land mammals have been found in New Zealand, but fossil sea mammals include whales and penguin-like birds.
New Zealand has many bird fossils from the last 30,000 years (before this there are few). Aside from penguins, the oldest bird found was a type of albatross. Fossilised bones of the large moa were first identified by Europeans in 1839, and collectors were keen to find more.
The best places to look for fossils are in river valleys, along the shoreline, and around coastal cliffs.