Close up of one of the Pipe Creek Sinkhole coprolites showing structures interpreted as hair (A) and a close-up of a mold in the coprolite thought to have been made by a hair (B). From Farlow et al, 2010.
Time and again I have stressed that every fossil bone tells a story, and, in a different way, so do coprolites. They are small snapshots of a moment in the life of an organism, often preserving bits of their meals, and while they 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, and 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 used CT scans, took thin sections, and employed other techniques to figure out the details of the fossils.
One of the teeth found in a Pipe Creek Sinkhole coprolite, as seen inside the coprolite (looking at the root of the tooth) and after its removal. From Farlow et al, 2010.
What the paleontologists found was that each coprolite – measuring 50 mm long √ó 26
mm maximum diameter and 30 long √ó 26 mm maximum diameter, respectively – was similar in chemical composition to coprolites produced by meat-eating animals. This was confirmed by remains discovered in one of the specimens. While one specimen lacked internal detail, the other (INSM 18.104.22.16800) preserved hairs and two teeth from a small carnivorous mammal, perhaps a skunk, indicating that whatever creature produced this scat was itself a carnivore.
The identity of the scat-maker itself, however, is difficult to determine. The enamel of the teeth found in the coprolite was eroded away, something which has been seen in coprolites attributed to crocodiles, but no crocodile remains have 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 authors state 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 are the large, meat-eating or omnivorous mammals of the site, and 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 cannot rule-out a large turtle as the scat-maker, on the basis of these observations they assign 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