TRACE FOSSILS FROM BOTH ENDS OF DEINOSUCHUS: LATE CRETACEOUS ESTUARINE CROCODYLIAN BITE MARKS AND COPROLITES FROM WEST GEORGIA

The giant eusuchian crocodylian Deinosuchus rugosus is abundantly represented by bones and teeth in the Late Cretaceous (Campanian) deposits in the Southeastern Coastal Plain, especially in the estuarine Blufftown Formation, western Georgia. Coinciding in the same deposits are many Pleurodire (Bothremydidae) turtle bones bearing large, circular bite traces, resembling larger versions of recent crocodile bite marks on modern bones. It is interpreted that these represent the preferred prey of D. rugosus in the southeastern USA. However, in at least one eastern site and in several coeval deposits on the western side of the continent, similar bite traces are found preferentially in dinosaur bones. These feeding choices suggest regional differences in prey opportunities or adaptive behavior by the same or sister Deinosuchus species in separated coastal regions in the Late Cretaceous.

Approximately 20 concretionary masses assumed to be fossil crocodylian feces are found in association with these bite traces in western Georgia. Six, larger, spindle-shaped coprolitic masses, tentatively attributed to Deinosuchus, range from 8.0 to 13.0 cm in length. They are cylindrical in cross section, laterally fusiform, and have tapering ends. Transversely and laterally cut or broken specimens of this morphology show poorly organized, internally concentric structure, with subtly sepate fracturing when broken. Minute bone fragments and small fish teeth are present on or near on the outer surfaces in most specimens, whereas the internal composition does not contain significant preserved bone. One specimen contains a well-preserved shark tooth (Squalicorax yangaensis) in the cortex. It is assumed that the intense dissolution of crocodylian digestive juices demineralized larger prey bones in the bulk of these coprolites, whereas vertebrate teeth on or near the outer surfaces accumulated after the feces were excreted and represent coprophagous feeding by bony fish and sharks. Smaller, relatively elongate and irregular coprolitic masses in the same localities are of more typical crocodylian fecal morphology, and may come from Borealosuchus sp., which is also in the known assemblage.