By Melissa Siver |
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The trilobites were found in shale layers lining the banks of a stream running under a bridge. The shale, which forms in books, was easily removed, and when split apart, tended to reveal a trilobite of varying quality. There were also hunks of shale in the river, which were harder and contained higher-quality fossils than the shale found on the riverbanks. Because the rocks are so easily removed, you must be careful to not over-collect this site and encourage too much erosion. The specimens we collected ranged in size from 5 mm to 3 cm lengthwise, and 4mm to 2 cm crosswise, and were very fragile. |
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These small trilobites, known as Naraoia Compacta, are soft-bodied arthropods that belong to the Crustacea family. Naraoia Compacta fossils have been found in many parts of the world, including Europe, Asia, and the Americas. In the Conasauga formation, they have been discovered alongside other fossils such as sponges, larger trilobites in the pytchopariid family, and large coprolites, giving us a picture of Naraoia?s underwater habitat. These well-preserved arthropod fossils are from the Middle Cambrian Period, 540 million years ago. The preservation of the trilobites is due to the high concentration of silica and iron in the shale, and the malleability of the substrate at the time that the trilobites died. |
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Although most of the fossils we found were of the trilobite Naraoia (Figure 1), we also found a fossil we could not identify (Figure 2). Because of its physiology, this particular creature could be related to Asaphida Asaphoidea, a hunter-scavenger trilobite that preyed on of the filter-feeding Naraoia. For rockhounds of all ages, the Conasauga Formation is an easy dig, requiring a minimum amount of tools, and which yields many fossils from the Cambrian seas. However, the collector must exercise care when handling the fossils and must also remember to respect the dig site. |
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