Fossils are part of our natural heritage and are non-renewable resources. For that reason, it is important to protect them so future generations can enjoy them and learn from them. Help the National Park Service protect fossil resources by practicing good stewardship. As you visit and enjoy the C&O Canal NHP, remember that it is illegal to remove any natural resource from a national park, including rocks and fossils.
For more information on paleontology in the National Park Service, visit the National Park Service Paleontology Program website: www.nature.nps.gov/geology/paleontology
Shells: Brachiopods, Bivalves and Gastropods
Animals with hard shells are more easily preserved than those made of soft materials. For that reason, paleontologists know that gastro-pods (snails), brachiopods (lamp shells), and bivalves (e.g., clams) have been around for over 500 million years. During the Paleozoic Era, gastropods and bivalves were a small part of marine communities, which were then dominated by brachiopods, corals and other marine animals. It wasn’t until after major extinctions reduced the number of these species that gastropods and bivalves went on to dominate marine environments. Although the heyday of the brachiopods has passed, a few orders still live in modern oceans.
Brachiopods and bivalves may look similar, but they are only distantly related. They both have two hinged external shells which are opened to feed and closed to protect themselves from predators. Most brachiopods have a small stalk which they use to anchor themselves to the substrate, though some forms burrow like mod-ern clams. These are the most common fossils found in the Park and are found in sedimentary rocks along the upper portions of the canal.
Crinoids and Bryozoans
Also known as “sea lilies,” crinoids resemble flowers with their long stems and wispy “petals.” In fact, crinoids are animals that use their feathery arms to strain food from the water. There are very few living crinoids today, but 450 million years ago, crinoid gardens were common features of shallow marine environments.
Bryozoans are tiny animals that live in communal structures that can take on a variety of shapes. Each bryozoan in the community has its own “window” in the structure through which it emerges to filter food from passing water currents. You can see parts of bryozoans and crinoid stems in some of the canal’s locks. Look for these fossils in the stone used for Locks 73, 74 and 75 as well as the Evitts Creek Aqueduct.
The oldest known fossils on earth belong to microscopic cyanobacteria (also known as blue-green algae) and are as much as 3 billion years old. No fossils in the C&O Canal NHP are that old, but the traces of cyanobacteria can be seen in the park as stromatolites. The fossils seen in the lock stones of locks 73, 74 and 75 are between 420-400 million years old. Stromatolites were important reef builders of the early Paleozoic but are today restricted to only a handful of localities on the planet. The Cyanobacteria that form stromatolites live in shallow water and need sunlight to pho-tosynthesize and grow. Stromatolites form when sediment is trapped by the sticky cyanobacteria; the cyanobacteria then grow upwards through the sediment cover to get sunlight. The newly exposed cyanobacteria are again covered with sediment, and the process repeats. The result is a wavy, thin-layered structure that can be many feet thick.
The chambered nautilus is the only living cepha-lopod with a shell, but during the Paleozoic Era, there were many different kinds. The first shelled cephalopods appeared in the Cambrian Period, and by the Ordovician, they had become the top predators in the oceans. Some were up to 30 ft long!
As the shelled cephalopods evolved, the shells took on a variety of shapes, including corkscrews and coils, during the Creteaceous. The earliest forms, however, were straight-shelled such as the one pictured.
Mineralized hard parts like bones or shells aren’t the only evidence of ancient life. Animals and plants also leave traces that reveal how they lived and grew or moved through their environments. Foot prints and burrows are two examples of trace fossils that paleontologists use to learn about extinct animals. There are many different kinds of burrows in the C&O Canal NHP made by differ-ent trace makers; most were made by worms that moved through the sediment in search of food. Visit the bridge over the canal at White’s Ferry to view some fossil burrows.
Last updated: December 18, 2017