Exceptionally well-preserved crocodilian coprolites from the Late Eocene of Northern Vietnam (Na Duong Formation) and their coproecological implications

Abstract

Reconstructing the paleoenvironment of Na Duong Basin by using coproecology is significant in understanding the intensive prey-predator relationships, the tropic relationship and the ecosystem evolution within the paleo-locality. A total of 55 measurable coprolites (IVPP V 27941/1 till IVPP V 27491/55) and numerous coprolite fragments from Na Duong fossil site were examined in this study. The putative coprolites were assigned to a crocodilian producer. Ichnosystematic studies further erected a new ichnogenus and species, which is Crococopros naduongensis ichnogen. et ichnosp. nov. for IVPP V 27491/46, based on a set of derived characters. Apart from quantitative analyses, a multi-disciplinary approach was also utilised for biogeochemistry analyses. The study has provided a rare and unique snapshot into the past where we believe an ancient river or lake-like environment has most likely existed in Na Duong Basin and was dominated by crocodilian fauna. We deemed that the Na Duong food chain was indeed ideal and healthy for the survival of the crocodilian species during that particular period of time with sufficient food sources. In addition, the study showed tangible evidence of the richness of ichnofauna, fauna, flora, the suitable climate, and paleoenvironment that supported Na Duong Basin as a fossil-Lagerstätte of Southeast Asia.