Opinions from E. D. Cope 1891
- 'Amia belongs to Halecomorphi'
- 'Amia macrospondyla belongs to Amia'
- 'Amia whiteavesiana belongs to Amia'
- 'Amiurus belongs to Nematognathi'
- 'Amiurus cancellatus belongs to Amiurus'
- 'Amiurus maconnellii belongs to Amiurus'
- 'Anchitherium westoni [misspelled as Anchitherium westonii] belongs to Anchitherium'
- 'Bunotheria belongs to Mammalia'
- 'Caenopus pumilus belongs to Caenopus'
- 'Chalicotherium belongs to Ancylopoda'
- 'Chalicotherium bilobatum belongs to Chalicotherium'
- 'Creodonta was reranked as a unranked clade and belongs to Bunotheria'
- 'Elotherium belongs to Artiodactyla'
- 'Elotherium arctatum belongs to Elotherium'
- 'Glires belongs to Mammalia'
- 'Halecomorphi belongs to Pisces'
- 'Hemipsalodon belongs to Oxyaenidae'
- 'Hemipsalodon grandis belongs to Hemipsalodon'
- 'Hypertragulus belongs to Oreodontidae'
- 'Hypertragulus transversus belongs to Hypertragulus'
- 'Leptomeryx belongs to Oreodontidae'
- 'Leptomeryx esulcatus belongs to Leptomeryx'
- 'Leptomeryx mammifer belongs to Leptomeryx'
- 'Leptomeryx semicinctus belongs to Leptomeryx'
- 'Macrotherium is a subjective synonym of Chalicotherium'
- 'Menodus angustigenis belongs to Menodus'
- 'Menodus selwynianus belongs to Menodus'
- 'Menodus syceras belongs to Menodus'
- 'Nematognathi belongs to Pisces'
- 'Oreodon belongs to Oreodontidae'
- 'Oreodontidae belongs to Artiodactyla'
- 'Oxyaenidae belongs to Creodonta'
- 'Palaeolagus belongs to Glires'
- 'Palaeolagus turgidus belongs to Palaeolagus'
- 'Palaeotherium (Menodus) was reranked as Menodus and belongs to Perissodactyla'
- 'Palaeotherium proutii is recombined as Menodus proutii'
- 'Perissodactyla belongs to Diplarthra'
- 'Rhineastes belongs to Nematognathi'
- 'Rhineastes rhaeas belongs to Rhineastes'
- 'Rhinoceros americanus is recombined as Menodus americanus'
- 'Rhinoceros occidentalis is recombined as Caenopus occidentalis'
- 'Stylemys belongs to Testudinata'
- 'Stylemys nebrascensis belongs to Stylemys'
- 'Testudinata was reranked as a unranked clade and belongs to Reptilia'
- 'Trionyx belongs to Testudinata'
- 'Trionyx leucopotamicus belongs to Trionyx'