Identification of basilosaurid archaeocetes (Mammalia, Cetacea) collected in Egypt by Richard Markgraf (1901–1916)

Chicago Field Museum FMNH P-12343 includes a cranium and dentary of a late Eocene archaeocete whale. These were acquired from the commercial fossil dealer Friedrich Kranz of Bonn in 1914–1915, after being collected by Richard Markgraf in Fayum, Egypt. Both were regarded as a single specimen identified in museum records as Prozeuglodon osiris . However, the cranium and dentary differ in preservation and in size, and cannot be parts of the same individual specimen nor belong to the same species. Comparison with other Fayum archaeocetes indicates that the cranium is Stromerius nidensis from the Qasr el-Sagha Formation, and the dentary is Dorudon atrox from the underlying Birket Qarun Formation. Fossils collected by Markgraf are found in museums all over the world, but he was neither a paleontologist nor stratigrapher, and identifications and ages of fossils he sold commercially cannot be accepted uncritically.