TALES FROM THE DIGESTIVE TRACT: COPROLITES, INCLUDING STRANDS OF FECAL PELLETS, AND STACKED LINGULIDS INTERPRETED AS HAVING BEEN EXCRETED BY A LINGULID-EATING ORGANISM, FROM THE CHAGRIN SHALE (FAMENNIAN) OF NORTHEASTERN OHIO

Coprolites found in concretions are a little studied component of the Chagrin Shale, a Famennian age rock unit containing a large assemblage of organisms dominated by ichnofossils, arthropods, and brachiopods. Larger (up to ± 3 cm) presumed coprolites contain remains of one or more crushed animal parts (e.g., Arthropoda and fish remains), and/or contain fine phosphatic material. Identification of producers is uncertain, but one concretion containing a fish tooth as well as a crushed Echinocaris carapace is suggestive, but not definitive, of fish predation. Strands (circa 1–3 cm long) of rounded to rod-shaped fecal pellets (1–2 mm long) are sometimes accompanied by fine phosphatic material. Pellets have internal structures (“pores” and particles), but internal features are not well organized, nor is any strong evidence for symmetry seen in thin sections of the pellets. Pellet strands are composed of pellets whose shape is suggestive of arthropods, but no definite link can be made. The pellets lack the organization typical of named species of Famennian and other arthropod fecal pellets. Width of the pellet strands indicate a moderate sized animal. Elongate strands (up to several cm in length) of lingulid shells are also presumed to be coprolites. Strands appear to be monospecific. The lingulid shells are stacked perpendicular, parallel, and/or at random to the length of the individual strands. Most lingulids in the strands are single valves that may be whole or fragmented, but in many cases both valves are preserved. Strands of lingulids indicate that the lingulid-eater was also a moderate sized animal with a gut that was a few millimeters thick. The lingulid-eating organism's diet was limited to lingulids, at least for the feedings represented by lingulid strands. It also preferred smaller lingulids, presumably because of availability close to the surface of the seafloor. There was no dearth of supply: lingulid shells are found in living position in some beds of the Chagrin Shale and lingulid trace fossils (Lingulichnus) are extremely common in some siltstone beds. A fish identity for the lingulid-eating organism is likely; extant Lingula are eaten by a number of demersal fishes, including sole (Cynoglossus spp.), and Lingula have been reported as comprising up to more than 90% of their diet.