First Record of Chimaeroid Fish (Holocephali: ’Edaphodontidae’) from the Lower Cretaceous of the Middle Volga Region

The record of a mandibular tooth plate of the chimaeroid fish Ischyodus sp. from the Lower Cretaceous deposits of the north of the Saratov Volga River Right Bank is described. The presumed age of the find is the Lower Aptian. This is the first recorded occurrence of chimaeroid remains in the Lower Cretaceous (pre-Albian) deposits of the Middle and Lower Volga regions, and the fourth record in deposits of this age in Eastern Europe. The composition of the global Early Cretaceous (pre-Albian) chimaeroid assemblage, including 3-4 genera of “edaphodontids” and 1-2 genera of rhinochimaerids, and the possible migration path of Ischyodus thurmanni to the southern hemisphere (Australia) in the Early Cretaceous are discussed.