A possible turtle swim track from the late Triassic of the Sichuan Basin, China

ABSTRACT

A possible turtle swim track from the Third Member of the Late Triassic Xujiahe Formation (Norian-Rhaetian) represents the oldest ichnological evidence of the group from China, supplementing previous reports of more abundant tracks from the Middle Jurassic of the region. The specimen is younger than the known pantestudinate (‘stem-turtle’) body fossils from China but matches the stratigraphic distribution of testudinate skeletons in other regions, for example, in Thailand, Europe and North America. Caution should be used to distinguish turtle swim tracks from those of crocodylomorphs and theropod dinosaurs, especially where only small samples are available. Therefore, we do not completely exclude an affinity with these groups or other archosaurs, such as phytosaurs. Nevertheless, the morphology of the imprints is most similar to turtle tracks, and it is most likely that an early non-crown group representative was the responsible producer. Of interest is also the depositional environment of the track-bearing deposit, which can be considered a deltaic plain marsh.

KEYWORDS:

• Turtle tracks
• late triassic
• Sichuan province

Acknowledgements

We are deeply grateful to Nasrollah Abbassi and anonymous reviewers for their invaluable, detailed and informative suggestions and comments on the drafts of this article. This research was funded by the National Natural Science Foundation of China (No. 41888101), the 111 project (B20011) and the Fundamental Research Funds for Central Universities (265QZ201903).

Disclosure statement

No potential conflict of interest was reported by the author(s).