Dinosaur tracks from the Jurassic-Cretaceous boundary Tuchengzi Formation (Hebei Province, China) used as building stones in the Chengde imperial summer resort: Age, ichnology, and history

Abstract

Slabs with tetrapod tracks from the Madigou Village quarry in the Tuchengzi Formation have famously been used as building stones at the imperial summer resort locality, also referred to in the ichnological literature as the “Chengde Summer Palace.” The Jurassic-Cretaceous boundary Tuchengzi Formation has elsewhere in the region yielded differently composed ichnofaunas with non-avian and avian theropod and sauropod tracks. The Madigou assemblage is remarkable because it shows the co-occurrence of abundant and diverse non-avian and avian theropod tracks. The non-avian theropod tracks are mostly Grallator- and Eubrontes-like with a few that registered faint hallux traces. A small number of didactyl deinonychosaurian tracks were recognized which we here label as Velociraptorichnus isp. The avian theropod tracks can tentatively be referred to Aquatilavipes and Koreanaornis, with wide digit divarications. Growing geochronological and biostratigraphic evidence suggests that these are among the oldest known bird tracks, similar in age to Pullornipes, also from the Tuchengzi Formation in northeastern China and dating close to the Tithonian-Berriasian boundary. Theropod tracks are dominating, even if an isolated possible sauropod track and some questionable tridactyl imprints that could either represent theropods or ornithopods, may indicate the presence of further dinosaur groups. The Tuchengzi ichnofauna is important because of the stratigraphic age close to the famous Jehol Biota.