Time and again I have stressed that every fossil bone tells a story, and, in a different way, so do coprolites. Fossilized feces are small snapshots of the lives of prehistoric organisms, often preserving bits of whatever they had been eating, and while coprolites may not get top billing in museum halls, they are among the most pungent reminders that weird and wonderful organisms really did live during the remote past. As reported by paleontologists James Farlow, Karen Chin, Anne Argast, and Sean Poppy in the latest issue of the Journal of Vertebrate Paleontology, two such vestiges of ancient digestive systems have recently been found in Indiana, but what left them is something of a mystery.
Called the Pipe Creek Sinkhole, the site where the coprolites were found dates back to around five million years ago. During that time Indiana was home to a motley assemblage of mammals. As stated by the authors, remains of “insectivores, rodents, hares, peccaries, deerlike ungulates, camelids, rhinoceroses, felids, canids, skunks, and bears” have been found there, but what sort of animal left the scat behind? To find out, the scientists attempted to parse the details of the fossils through thin sections and CT scans.
What the paleontologists found was that the coprolites – measuring 50 mm long × 26 mm maximum diameter and 30 long × 26 mm maximum diameter, respectively – were similar in chemical composition to scat produced by meat-eating animals. This was confirmed by remains discovered within one of the specimens. While one coprolite lacked internal detail, the other (INSM 188.8.131.5200) preserved hairs and two teeth from a small carnivorous mammal, perhaps a skunk, indicating that whatever creature produced the scat was itself a carnivore.
The determination that the coprolites were made by a meat-eating animal narrowed down the list of suspects, but the actual identity of the scat-maker proved difficult to ascertain. The enamel of the teeth found in the coprolite was eroded away, something which has been seen in coprolites attributed to crocodiles. The trouble was that no crocodile remains had been found at Pipe Creek Sinkhole. Additionally, while the scats were similar to those made by snapping turtles observed by the scientists in aquaria, the researchers stated that they are doubtful that the scats were left by a turtle due to the relatively large size of the scats and the lack of enamel-eroded teeth in the modern samples for close comparison.
The only other candidates were the large, meat-eating or omnivorous mammals of the site. Of those animals, it seemed most likely that the scats were left by a canid, especially since experimental tests of how dogs consume and digest white-tailed deer jaws have previously confirmed that whole teeth can sometimes make their way into the stomach where their enamel is dissolved before being deposited as scat. While the authors could not rule-out a large turtle as the scat-maker, on the basis of these observations they assigned the coprolites to a wolf-sized canid. Regardless of the identity of what animal left the scat, though, it is wonderful that such signs of ancient life have been preserved, and through using techniques like those employed in this study paleontologists can begin to better resolve the paleobiology of long-dead organisms.
James O. Farlow; Karen Chin; Anne Argast;Sean Poppy (2010). Coprolites from the Pipe Creek Sinkhole (Late Neogene, Grant County, Indiana, U.S.A.) Journal of Verterbrate Paleontology, 30 (3), 959-969 : 10.1080/02724631003762906