Turtle Shell Impression in a Coprolite from South Carolina, USA

ABSTRACT

Coprolites (fossilized feces) can preserve a wide range of biogenic components. A mold of a hatchling turtle partial shell (carapace) referable to Taphrosphys sulcatus is here identified within a coprolite from Clapp Creek in Kingstree, Williamsburg County, South Carolina, USA. The specimen is the first-known coprolite to preserve a vertebrate body impression. The small size of the turtle shell coupled with the fact that it shows signs of breakage indicates that the turtle was ingested and that the impression was made while the feces were still within the body of the predator. The detailed impression could only have survived the act of defecation if the section of bony carapace was voided concurrently and remained bonded with the feces until the latter lithified. Exceptionally, the surface texture of the scutes is preserved, including its finely pitted embryonic texture and a narrow perimeter of hatchling scute texture. The very small size of the shell represented by the impression makes it a suitable size for swallowing by any one of several large predators known from this locality. The coprolite was collected from a lag deposit containing a temporally mixed vertebrate assemblage (Cretaceous, Paleocene and Plio-Pleistocene). The genus Taphrosphys is known from both sides of the Cretaceous–Paleogene (K–Pg) boundary so, based on the size of the coprolite and the locally-known predators, the juvenile turtle could have been ingested by a mosasaur, a crocodylian, or a theropod dinosaur. Unlike mosasaurs and theropod dinosaurs, crocodylian stomachs have extremely high acid content that almost always dissolves bone. Therefore, the likely predator of this turtle was a mosasaur or a (non-avian or avian) theropod dinosaur.

KEYWORDS:

• Coprolite
• Turtle shell impression
• Taphrosphys
• Bothremydidae
• Testudines
• Theropod
• Dinosaur
• Bird
• Mosasaur
• Crocodylian

Acknowledgments

CMM-V-4524 was collected by one of us (BP). Numerous helpful comments provided by W. Joyce (University of Fribourg) and an anonymous reviewer significantly improved our paper, especially the interpretation of the surface texture of this remarkable find; thank you! We would also like to recognize the improvements made by the Associate Editor. M. Gingras edited this contribution for Ichnos, many thanks. J. Pojeta (United States Museum of Natural History, the Smithsonian Institution) provided liberal access to his lab where the coprolite was whitened with sublimed ammonium chloride. Kenneth Tighe made the Smithsonian collection of modern turtles available to us for comparison of them with our specimen.

Funding

This article was made possible by funding from the citizens of Calvert County, the Board of Calvert County Commissioners and the Clarissa and Lincoln Dryden Endowment for Paleontology at the Calvert Marine Museum.