17 Mart 2013 Pazar

State Fossil of Georgia

State Fossil of Georgia

Shark Tooth (common name)
Since shark skeletons are composed of cartilage rather than bone, shark teeth are often the only part of a shark to fossilize and survive hundreds of millions of years. Sharks continually shed their teeth, up to tens of thousands in a lifetime, making shark tooth fossils plentiful. Approximately 2,000 species of fossil shark have been described.
Fossils mainly date from the Miocene epoch through the late Cretaceous period, making them approximately 8 to 150 million years old. Fossilized shark teeth of up to 450 million years of age have been found. Most commonly black or shades of gray, fossil shark teeth can also be white, brown, and even shades of red and blue. The minerals present in the sediment surrounding the tooth determine its color.
Fossilized shark teeth are relatively common on the Georgia coastal plain. In 1976, the shark tooth was designated the official fossil of the state of Georgia.
To become fossilized, an object must be quickly covered with sediment before it has a chance to decompose. Over thousands of years, minerals such as calcite and silica in the water are deposited into the open spaces in the specimen. For this reason, fossilized shark teeth, like all fossils, are found in sedimentary rock or sediment.
Fossilized shark teeth are found in marine-derived rock and sediment near riverbeds, in sand pits, and on beaches. Sometimes calcified shark vertebrae are also found. These are commonly found in Cretaceous and Cenozoic deposits. These fossils are abundant on and near the coasts of the southeastern and western United States and in Oceania. One notable location for shark fossils is a phosphate mine in Polk County, Florida, known as Bone Valley.
Evolution of one shark into another, coupled with the lack of other fossilized body parts, creates difficulty in determining exactly what species of shark a tooth came from. The shape, size, and location the tooth once occupied in the shark’s mouth can reveal important information about the behavior, habitat, anatomy, age, sex, and diet of that shark, as well as how an extinct species compares with a living one. Paleontologists have gained clues about prehistoric shark breeding, birthing, and feeding from these fossils. For example, they can determine a shark nursery area, chosen by mother sharks because it has fewer predators, based on an abundance of juvenile teeth in a given area.
In the first century CE, Pliny the Elder was the first to record findings of fossilized shark teeth. Pliny believed that lunar eclipses caused these fossils to fall from the sky. During the Renaissance, shark fossils were thought to be fossilized tongues and were worn as good luck charms. In 1667, Danish naturalist Nicholas Steno corrected these beliefs when he wrote a book about shark teeth. This book documented the first understanding that fossils provide clues to history.
Shark teeth were used for tools and weapons, as well as for carving wood and pottery, by the native peoples of America and Oceania. Today, they are particularly prized by collectors. The most sought-after shark fossil is the serrated tooth of the largest marine predator that ever lived, the megalodon, which is thought to have been about 40 feet (12 m) long. One of the most famous places to locate these teeth is the shores of Calvert County, Maryland.

Click to enlarge an image
State Prehistoric Creature
Collection of Shark Teeth
State Prehistoric Creature
Single Shark Tooth

Author: World Trade Press

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