paleobiology

Trilobite trace fossils

If you ever happen to find yourself at the Clinch Mountain Lookout Restaurant in Thorn Hill, Tennessee, be sure to 1) try a piece of their vinegar pie and 2) ask to check out the spectacular outcrop featuring trilobite trace fossils directly behind the restaurant.

Trace fossils are not remains of the organism itself (i.e. a body fossil) but rather are indirect records of an organism via its biological activity. Burrows are among the most common trace fossils, and the most well-known trace fossils may be the Laetoli hominin footprints. The organism itself is rarely found preserved in direct association with the trace fossil it created, so trace fossils can be key in unraveling the behavior of ancient extinct organisms.

These specific trilobite trace fossils are called rusophycus, which are formed when a trilobite is resting and partially buried in the muddy bottom sea sediments. This activity leaves a bi-lobed impression that can be accompanied by parallel marks corresponding to its legs.

The trace fossils at this location are found in the Silurian Clinch sandstone, but elsewhere in Tennessee, trilobite trace fossils in the Cambrian Rome Formation provide evidence for trilobite expansion into tidal flats and landward during this earlier time.

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