On Saturday 12th 2000, my family and I went on a float trip on the Huzzah River in Steelville, Missouri. The Huzzah River and its surroundings were a perfect location for me to look for my fossil. Since the water level was shallow, that enabled me to look to the river bottom. Almost immediately after I began my search near the edge of the river, I spotted a rock that appeared to have some sort of shell embedded in it. I decided this would be a good specimen for me to try to examine and identify. After returning from our float trip on Sunday, I spent some time trying to locate and identify the rock I had found in the books I had checked out of the library. After some searching through the books, I concluded that I had found a fossil.
What is a fossil? The word fossil is derived from Latin and means to dig or to be dug up. A fossil is the preserved remains of a plant or animal, which lived more than ten thousand years ago. They give some idea of the size, shape, and form of the once living animal or plant. Fossils are most likely to be preserved where the conditions for decomposition are poorest and where moisture, oxygen or warmth are excluded (Parker 32).
Fossils are usually categorized in two different ways, unaltered or altered. An example of an unaltered fossil are shells buried in the mud of the sea floor or even whole carcasses of large mammals from the Ice Age that have been found frozen and preserved in ice for as long as twenty five thousand years. Another example are insects like mosquitoes, that have been preserved by being encased in amber (Unklesbay 19).
Altered fossils are fossils that have been preserved as the result of alteration of the buried organism, usually its hard parts. These alterations can take place under six forms. Replacement fossilization is when part of the original material has been dissolved and some other substance has taken its place. The fossilization process when mineral substances are introduced to the pores of porous materials such as bones and shells is called permineralization. The soft parts of organisms contain nitrogen, oxygen, carbon and hydrogen. In distillation, all of these except carbon are removed during the fossilization process. Another example of altered fossils are molds and casts. This process of fossilization is achieved when a hard part of an organism leaves an impression in soft mud and is later removed, leaving the impression to be preserved in the mold. Animals can also leave footprints and tracks in mud that is then hardened to form a rock. After examining my fossil, I decided I had found an altered fossil. It was a stropheodonta brachiopod, and it had undergone permineralization fossilization (Unklesbay 20).
It is believed the earth was formed about four and a half billion years ago. A time scale has been developed by scientist, which divides geological time into periods based on climatic and geological changes.
The period from the beginning of the earth, to about five hundred and seventy million years ago is known as the Cambrian period. There was no life on land, but there were jellyfish, sponges, and shelled animals like brachiopods and trilobites in the sea. The Ordovician period is from five hundred million years ago and the Silurian period was from four hundred and thirty million years ago. During this time, the first animals, scorpions, and millipedes came out of the water onto land. From about three hundred and ninety five million years ago to about two hundred and twenty five million years ago are the Devonian, Carboniferous, Permian, and Triassic period. The first reptiles appeared, along with land invertebrates and ancestors of mammals and dinosaurs. During the Jurassic, Cretaceous, Paleocene Epoch, Eocene Epoch, Oligocene Epoch, Miocene Epoch, and the Pliocene Epoch time periods, which occurred from one hundred and ninety three million years ago to five million years ago, dinosaurs, mammals, and the first human ancestors appeared. The final two periods are the Pleistocene Epoch and the Holocene Epoch periods during which many large mammals disappeared and human civilization began (Parker 110-111).
Brachiopods date back all the way to the Cambrian time period, but were probably more abundant during the Carboniferous period. The Carboniferous period or the “Age of Amphibians” as it is known, lasted for seventy four million years, from three hundred and sixty million to two hundred and eighty six million years ago. During this time period, the continents drifted around the globe. North America and Europe slowly collided to form the continent of Laurasia and the Caledonian mountains also appeared at this time. Much of North America was inundated by a warm and shallow sea and was full of abundant plant life, invertebrates, and fish. Because it was a very hot and humid environment, there were plenty of insects like centipedes, millipedes, cockroaches, and giant dragonflies. Marine invertebrates, like crinoids, brachiopods, and corals, were abundant. Fish and amphibians thrived. Since the seas were shallow, they formed coastal lakes and lagoons, which supported huge, forested swamps. The vegetation that lived during this period rotted, turned into peat, and eventually became coal. During this period, most of the world’s coal deposits were laid down. (Garcia 5-9).
Because oxygen in the air reached levels that provided adequate protection from the sun’s ultraviolet rays, amphibians were able to escape the cover of water for the first time. The first land animals, the reptiles, evolved from amphibians toward the end of the Carboniferous period. Amphibians probably crawled from the water to the damp forests in search of invertebrate prey. When they evolved, some were sturdy and as big as a crocodile; others had tiny limbs, while still others soon lost their newly acquired limbs and slithered of snake-like. The first reptiles were the cotylosaurs and the pelycosaurs. They developed the shelled egg that could be laid on dry land. They also acquired a scaly, leathery skin that resisted the suns heat. Reptiles had finally broken their ties with water and were able to roam the land. Some of these reptiles are similar to those that walk the earth today. This was what the earth was like when brachiopods were copious (Parker 122-129).
Brachiopods are one of the most common fossils in Missouri. Brachiopods are bivalved marine organisms. They consist of a group of shell-bearing marine invertebrates, which have existed since early Cambrian time. The shell of the brachiopod consists of two parts that can be opened or closed by the muscle system of the animal. A characteristic that helps distinguish the brachiopod from other invertebrates is its feeding and breathing organ called lophophore. Lophophores are tentacles that extend from both sides of the mouth. Brachiopods vary in size. Some are only a fraction of an inch in length and others reach as much as eleven inches. They frequently grow in groups attached to rocks, pilings, or other objects in the seawater. They prefer shallow, well-circulated seawater. Because there are nearly three hundred species of brachiopods alive today, they are known as living fossils, and this will ensure that brachiopods will be found for generations to come (Unklesbay 36-37).
Since most of North America was underwater during the Carboniferous period, this would explain why brachiopods and other invertebrates are so widely found in Missouri. Missouri’s many rivers and flood plains are excellent places to search for fossils. Fossil collecting is important because it shows what life was like in the ages that have passed. Fossil hunting is a window to the past that may help people in the future see what problems occurred and caused massive extinctions in the earth. With knowledge from the past, future generations may be able to avoid these same mistakes.