First occurrence of hadrosaurid (Dinosauria: Ornithopoda) remains from the Nenjiang Formation (early Campanian) in the Songliao Basin, Northeast China

We describe the first hadrosaurid fossils from the Upper Cretaceous Nenjiang Formation (early Campanian) in the Songliao Basin, Northeast China. The material comprises an isolated tooth, three dentary fragments, and several fragmentary postcranial bones consisting of dorsal, sacral, and caudal vertebrae, as well as fragments of the pubis, ischium, and fibula. Morphological analyses indicate that the postcranial material can be assigned to Lambeosaurinae. These lambeosaurine remains represent a rare record of the early divergence of this group, supporting the hypothesis of an Asian origin for lambeosaurines and their subsequent dispersal to North America. This study expands the known geographic and temporal distribution of hadrosaurids, highlights the significance of the Nenjiang Formation in documenting dinosaur diversity, and provides valuable insights into the terrestrial ecosystems of the Songliao Basin during the Late Cretaceous.