Pit 4 Grundy County , IL
See map: Google Maps
This coprolite contains numerous plant fragments that are visible under magnification. Although it is impossible to determine what creature expelled this high fiber clump, herbivore coprolites of this size are generally attributed to Arthropleura, giant millipede arthropods. Reaching lengths of 2 m (6.5 feet), these are the only known herbivores large enough to have produced a fecal mass of this size.