New Evidence for a Cretaceous Age for a Mesozoic Nonmarine Bivalve Assemblage from Paekto‐dong, Sinuiju City, The Democratic People's Republic of Korea

The Sinuiju Formation in Paekto‐dong, Sinuiju City in the Democratic People's Republic of Korea has yielded Mesozoic nonmarine bivalve fossils, which is the first occurrence of such in the DPRK. Based on these fossil specimens, a new Cretaceous bivalve assemblage, the Arguniella yanshanensis‐Sphaerium anderssoni Assemblage is erected. This assemblage includes Arguniella yanshanensis, A. lingyuanensis and Sphaerium anderssoni and can be compared with the Jehol Biota. The age of the Sinuiju Formation is also clarified and on the basis of the bivalves and the presence of a Eosestheria–Ephemeropsis–Lycoptera (E–E–L) assemblage, the formation is not Upper Jurassic, but Lower Cretaceous in age.