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Chapter 2: Common fossils
Fossils are ancient forms of life, and so are classified in just the same way as modern forms of life.
Classification of living things moves from large groups that share basic similar features (kingdoms), down to much smaller groups containing only those members that can breed together.
The largest group is the kingdom. Animals are put in one kingdom, plants in another.
The kingdoms are divided into broad groups
called phyla (singular phylum). A phylum may contain many thousands of species. The largest phylum, arthropoda, for example, contains all the insects, spiders, crustaceans, and trilobites.
Phyla are divided into classes. Insects, spiders, crustaceans and trilobites all belong to different classes.
Classes are subdivided into orders, then into families, then into genera (singular genus),
and finally into species. In this book, both
genera and species names are shown
in italics.
Most fossils can be identified
relatively easily by genera, but usually
only a specialist can identify an individual
species. Thus, the distinctive colonial coral, which is often referred to as Favosites, is a genus within the phylum Coelenterata. The word genera leads
to the expression ‘generic name’, which is the name most commonly used when describing fossils.
The number of common fossil genera is still large – over a thousand – but at least it is manageable after practice.
It is important to remember that only a few fossils remain to represent the innumerable living things that have inhabited this world. Furthermore, nine-tenths of fossils are those of marine life, because it is far easier for sea creatures to be buried and preserved in the calm, still, and oxygen-poor waters of an ocean than in the continuously disturbed environments on land.
(Below) Ammonites were very successful animals and are found through a significant section of geological time. They evolved quickly and developed distinctive shell patterns. Because they were also widespead, they make good fossils, which can be identified relatively easily (they can be used as index fossils). This makes ammonites very useful, particularly for the Mesozoic Era.
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