Opinions from E. D. Cope 1881
- 'Acoessus belongs to Menodontidae'
- 'Anchilophus belongs to Palaeotheriinae'
- 'Anchippus belongs to Palaeotheriinae'
- 'Anchitherium belongs to Palaeotheriinae'
- 'Aphelops belongs to Rhinoceridae'
- 'Atelodus belongs to Rhinoceridae'
- 'Caenopus belongs to Rhinoceridae'
- 'Ceratorhinus belongs to Rhinoceridae'
- 'Chalicotheriidae belongs to Perissodactyla'
- 'Chalicotherium belongs to Chalicotheriidae'
- 'Coelodonta belongs to Rhinoceridae'
- 'Colonoceras belongs to Lophiodontinae'
- 'Diceratherium belongs to Rhinoceridae'
- 'Diplacodon belongs to Menodontidae'
- 'Elasmognathus belongs to Tapiridae'
- 'Equidae belongs to Perissodactyla'
- 'Equus belongs to Equidae'
- 'Equus (Protohippus) was reranked as Protohippus and belongs to Palaeotheriinae'
- 'Helaletes belongs to Lophiodontinae'
- 'Hippidion is corrected as Hippidium and belongs to Equidae'
- 'Hippotherium belongs to Palaeotheriinae'
- 'Hyrachyus belongs to Lophiodontinae'
- 'Hyracodon belongs to Hyracodontidae'
- 'Hyracodontidae belongs to Perissodactyla'
- 'Hyracotheriinae belongs to Lophiodontidae'
- 'Hyracotherium belongs to Hyracotheriinae'
- 'Hyracotherium siderolithicum belongs to Hyracotherium' according to Pictet 1869
- 'Hyracotherium siderolithicum is recombined as Acoessus siderolithicum'
- 'Lambdotherium belongs to Chalicotheriidae'
- 'Leurocephalus belongs to Chalicotheriidae'
- 'Limnohyus belongs to Chalicotheriidae'
- 'Listriodon belongs to Tapiridae'
- 'Lophiodon belongs to Lophiodontinae'
- 'Lophiodontidae belongs to Perissodactyla'
- 'Lophiodontinae belongs to Lophiodontidae'
- 'Lophiotherium belongs to Hyracotheriinae'
- 'Macrauchenia belongs to Macraucheniidae'
- 'Macraucheniidae belongs to Perissodactyla'
- 'Meniscotherium belongs to Chalicotheriidae'
- 'Menodontidae belongs to Perissodactyla'
- 'Mesohippus belongs to Palaeotheriinae'
- 'Nestoritherium belongs to Chalicotheriidae'
- 'Pachynolophus belongs to Lophiodontinae'
- 'Palaeosyops belongs to Chalicotheriidae'
- 'Palaeotheriidae belongs to Perissodactyla'
- 'Palaeotheriina was reranked as the subfamily Palaeotheriinae and belongs to Palaeotheriidae'
- 'Palaeotherium belongs to Palaeotheriinae'
- 'Palaeotherium (Menodus) belongs to Palaeotherium' according to Pomel 1848
- 'Palaeotherium (Menodus) was reranked as Menodus and belongs to Menodontidae'
- 'Paloplotherium belongs to Palaeotheriinae'
- 'Peraceras belongs to Rhinoceridae'
- 'Pliolophus belongs to Hyracotheriinae'
- 'Propalaeotherium belongs to Chalicotheriidae'
- 'Rhagatherium belongs to Chalicotheriidae'
- 'Rhinoceros [misspelled as Rhinocerus] belongs to Rhinoceridae'
- 'Rhinocerotidae is corrected as Rhinoceridae and belongs to Perissodactyla'
- 'Symborodon belongs to Menodontidae'
- 'Taperidae is corrected as Tapiridae and belongs to Perissodactyla'
- 'Tapirus belongs to Tapiridae'
- 'Triplopodidae [misspelled as Triplopidae] belongs to Perissodactyla'
- 'Triplopidae is a misspelling of Triplopodidae'
- 'Triplopus belongs to Triplopidae'
- 'Triplopus cubitalis belongs to Triplopus'
- 'Zalabis belongs to Rhinoceridae'