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Fossils

Introduction to Fossils

Fossils are the remains or traces of prehistoric plants and animals. Fossils have been discovered that represent most living groups, even those that are now extinct, some dating back 3.5 billion years.

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Fossils are records of ancient life on Earth. They contain evidence of how life has changed and evolved throughout the earth's history and provide a tangible link to the past. Fossils of extinct organisms are compared with living organisms to draw conclusions about their nature, behavior, and habits. When combined with geology, fossils provide evidence of where ancient life lived.

In order to locate a place where fossils might be found, it's helpful to understand what kinds of fossils there are and how they were formed, so you can pinpoint the right places where the conditions existed to make fossils.

How Fossils are Formed

There are many kinds of fossils but there are only a few ways they are formed.

Most fossils are found in rock. When fossils are found this way, it indicates that the fossil went through a special process.

The plant or animal died in or near water where the remains were quickly covered by layers upon layers of sediment. The remains decayed leaving a 'hole' in the layers of sediment where minerals dissolved in the water, collected, and eventually replaced the remains. All this time, the pressure of layers of sediment turned the sediment, and the minerals collected in the fossil, into stone. Often, only the hardest parts of the remains will become fossilized. This is because shells, bones, claws, and teeth already contain minerals.

Even after the it has become rock, the fossil may still go through transformation. Heat from volcanic activity and movements of the earth's crust may deform the fossil.

Not all fossils are found in rock. Insects, for example, have been found encased in amber. Some fossils have been 'freeze-dried' and others covered with volcanic ash.

How the fossil was formed is as interesting itself.

Where to Find Fossils

Fossils can be found in an area in which sedimentary rocks, such as clay, shale, and limestone are exposed. Sometimes the best places to look are artificial exposures such as road cuts or quarries. A geological map can also help to find fossils.

Researching before heading out to a site to familiarize yourself with its characteristics is a good idea. Visiting a local museum is often useful, but up-to-date information from other collectors is better. Joining a local natural history society would prove most helpful.

These societies are often able to gain access to areas that may be restricted to the general public. Most societies have a code of conduct for fossil collecting. Wherever it is decided to collect fossils, get permission from the authorities.

What Can Be Learned From Fossils

Fossils can be divided into two main catagoiries: macrofossils and microfossils. Microfossils are fossils that are too small to be seen without a microscope. Pollen, bacteria, and single-cell organisms can be found as fossils but are often overlooked. Macrofossils are easier to find. Fossilized plants and animals, and their parts and traces are all macrofossils.

Microfossils are tiny, but recognizable, bits of plant or animal matter. They occur in thousands of different forms, but the most common are pollen grains, spores, reproductive structures of fungi, and numerous walls of microscopic algae. These are all invisible to the unaided eye, but easily recognized in a microscope. Microfossils are informative and abundant, occurring in many kinds of sediment. This is easy to understand if you think about how many tiny grains of pollen blow around every year in British Columbia.

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Plant fossils, especially pollen and spores, provide paleobotanists with one of the most powerful tools of understanding the history of ecosystems and the processes that shape them. Any change of the landscape immediately results in a change in the types of plants that grow there. Plant fossils also document changes in climate. Palms, for example, tend to live in warm regions, spruce trees thrive where the weather grows cold, and ferns require a great deal of moisture. Grasses and most cacti tend to get along with much less moisture.

Macrofossils are fossils that most people are familar with. They include plants and animals. These body fossils are the preserved remains of the organism itself. The most common body fossils found are from the hardest parts of the body, including bones, claws, teeth and seeds. More rarely, fossils have been found of softer body tissues. Prehistoric creatures shed their shells much like some of today's marine creatures do. Thus, shielded parts of animals have been found fossilized also.

Bones are the main means of learning about animals. By mapping out how bones are lying in the ground, scientists find out how the specimen was deposited and perhaps how it got there. Looking for marks on the bones (teeth marks, for example) may tell us about what type of animal fed on it. Studying the bones helps scientists to identify the type of animal, discover new species of dinosaurs, and how they relate to present day creatures such as turtles, crocodiles, lizards, and other amphibians.

Trace fossils (also known as ichnofossils) are the impressions of an organism in the sediment, or marks made by it in life. Trace fossils record the movements and behaviors of the dinosaurs. There are many types of trace fossils including trackways (footprints), toothmarks, gizzard rocks, coprolites, burrows, and nests. Even the lack of trace fossils can yield information; the lack of tail-furrow fossils indicates an erect tail stance for dinosaurs that were previously believed to have dragged their tails.

Trackways were usually made in mud or fine sand, and have been found at over 1500 sites, including quarries, coal mines, riverbeds, deserts, and mountains. These fossils are in abundance because dinosaurs made many tracks with their constant movement, and because tracks fossilize so well. Fossil footprints can provide paleontologists with information about speed and length of the stride of the dinosaur, whether they walked on two or four legs, and the bone structure of the foot. Things such as stalking behavior, and existence of dinosaur herds and stampedes can also be gathered from trackways. Unfortunately, linking a set of tracks with a particular species of dinosaur can prove to be quite difficult.

As with modern birds, dinosaurs swallowed stones to help grind their food. These are known as gizzard rocks, or gastroliths (literally meaning stomach-stones) and have been found as fossils. They are usually smooth, polished, and rounded, but are hard to distinguish from river rocks. Be skeptical of any gizzard rocks found in Mesozoic deposits unless they are found in the ribcage of dinosaur remains.

Coprolites (fossilized feces) yield information about the dinosaur's diet and habitat. Coprolites can show either body fossils of plant material (indicating a herbivorous diet) or bones (indicating a carnivorous diet). They provide information about habitats and the presence of dinosaurs in areas otherwise lacking dinosaur body fossils or other trace fossils (such as tracks).

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Eggs, embryos, and nests are also included in the trace fossil category. Preserved embryos help to match an egg with a species of dinosaur, and also shed light on dinosaur development. The nests and clutches of eggs reveal much about dinosaurs' nurturing behavior.

Because British Columbia was under water in prehistoric times, it's unlikely that any eggs, embryos, and nests will be found. Many large marine reptile fossilized skeletons have been found in British Columbia, however, along with significant discoveries of Cambrian life.

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