1. Research Center of Paleontology & Stratigraphy, Jilin University, Changchun 130026, China;
2. Royal Belgian Institute of Natural Sciences, Brussels 1000, Belgium;
3. The Dinosaur Museum of Jiayin, Jiayin 158000, Heilongjiang, China

Abstract: Hadrosauridae is taxonomically subdivided into the Hadrosaurinae and Lambeosaurinae based mainly on the skull characteristics. Hadrosaurid fossils are particularly abundant in Upper Cretaceous of Yuliangzi Formation from Longgushan of Jiayin, Heilongjiang. Mandschurosaurus amurensis (Riabinin, 1925) , the first dinosaur fossil found from China, was discovered in this locality and belongs to hadrosaurinae. Charonosaurus jiayinensis (Godefroit et al. , 2000) was also excavated here and belongs to lambeosaurinae. The authors describe a partial left dentary with dozens teeth from the Longgushan, and this new fossils clearly belong to hadrosaurinae. Because it is characterized by the following synapomorphies: 5 teeth ormore in each alveolus of the dentary and dentary marginal denticles reduced to small papillae along the dorsal half of the crown. Well developed secondary and tertiary ridges on the lingual side of the dentary crowns are unusual in hadrosaurids. The newly discovered fossil is obviously different from Charonosaurus jiayinensis occurred in the same place, while the comparisons with Mandschurosaurus amurensis are difficult, because the dentary referred to the holotype of this taxon lacks teeth in preservation.