Footprint on a coprolite: A rarity from the Eocene of Vietnam

A rare ichnological example of a crocodilian footprint on an Eocene crocodilian coprolite has been discovered. The enigmatic specimen, measuring 4 cm in length, was found among 100 coprolites at the Na Duong coal mine in Lang Son province, northern Vietnam. Almost all the discovered coprolites were ascribed to a potential crocodilian producer, suggesting the existence of an ancient lacustrine environment. Furthermore, neoichnological analyses of extant crocodilian footprints also corroborate the inference of a crocodilian as the producer of the footprint. We concluded that the 4-cm-long Na Duong fingerprints most likely belonged to a 2-m-long crocodilian whose IV or V finger of the right manus might have made the fingerprints. Since no other records of foot traces or trackways were identified during the fieldwork in the fall of 2018, the Na Duong fossil site should be investigated for further ichnofossil analysis.