Well-Preserved Grallator Tracks Associated with Microbial Mats from the Jurassic–Cretaceous Boundary of the Tuchengzi Formation, Hebei Province, China

The Tuchengzi Formation, located in the western Liaoning region, has been a hotspot for dinosaur track research in the past decade. Situated within the Jurassic–Cretaceous boundary sequence, it has yielded at least 17 known theropod-dominated tracksites. This study documents two new sites, Lishi II and Lishi III. Sauropod tracks have been identified at Lishi II and are assigned to Brontopodus. Tridactyl theropod tracks at Lishi II and Lishi III are categorised into morphotypes A and B. Morphotype A shows striking similarities to Upper Jurassic Grallator tracks from Europe and also to the Lower Jurassic Grallator type material from Massachusetts, USA, and thus is classified as Grallator isp. Morphotype B exhibits characteristics more consistent with the holotype specimen of the Asian Grallator ssatoi. Wrinkle structures on the track-bearing surface indicate the presence of microbial mats, which likely played a significant role in the formation and preservation of the tracks. Moreover, the Lishi II and Lishi III track assemblages are a rare example of Cretaceous grallatorids from East Asia that exhibit considerable morphological similarity to typical grallatorids from the Early Jurassic. Additional studies are needed to better understand the diversity of grallatorids during the Early Cretaceous worldwide, and in the Tuchengzi Formation in particular.