2015, an extensive study of diplodocid relationships by Emanuel Tschopp, Octavio Mateus, and Roger Benson concluded that Brontosaurus was indeed a valid genus of sauropod distinct from Apatosaurus. The scientists developed a statistical method to more objectively assess differences between fossil genera and species, and concluded that Brontosaurus could be "resurrected" as a valid name. They assigned two former Apatosaurus species, A. parvus and A. yahnahpin, to Brontosaurus, as well as the type species B. excelsus.[3] Paleontologist Michael D'Emic made a critique.[6] Palaeontologist Donald Prothero criticized the mass media reaction to this study as superficial and premature, concluding:
Until someone has convincingly addressed the issue, I’m going to put “Brontosaurus” in quotes and not follow the latest media fad, nor will I overrule Riggs (1903) and put the name in my books as a valid genus