Opinions from J. Leidy 1857
- 'Agriochoerus antiquus belongs to Agriochoerus'
- 'Agriochoerus major belongs to Agriochoerus'
- 'Amphicyon gracilis belongs to Amphicyon'
- 'Archaeotherium mortoni is recombined as Elotherium mortoni'
- 'Archaeotherium robustum is a subjective synonym of Entelodon mortoni'
- 'Arctodon is a subjective synonym of Entelodon'
- 'Camelops kansanus belongs to Camelops'
- 'Cladocyclus occidentalis belongs to Cladocyclus' according to Leidy 1856
- 'Cladocyclus occidentalis belongs to Cladocyclus'
- 'Clupea humilis belongs to Clupea'
- 'Compsemys victus is corrected as Compsemys victa and belongs to Compsemys'
- 'Cotylops speciosa is a subjective synonym of Oreodon culbertsoni'
- 'Crocodilus humilis belongs to Crocodilus'
- 'Daphoenus vetus is recombined as Amphicyon vetus'
- 'Deinodon horridus is recombined as Megalosaurus (Deinodon) horridus'
- 'Dinictis felina belongs to Dinictis'
- 'Emys culbertsonii is a subjective synonym of Testudo nebrascensis'
- 'Emys hemispherica is a subjective synonym of Testudo nebrascensis'
- 'Emys obscurus belongs to Emys'
- 'Emys oweni is a subjective synonym of Testudo nebrascensis'
- 'Enchodus shumardi belongs to Enchodus'
- 'Entelodon ingens belongs to Entelodon'
- 'Eucrotaphus auritus is a subjective synonym of Agriochoerus major'
- 'Eucrotaphus jacksoni is a subjective synonym of Agriochoerus antiquus'
- 'Eumys elegans belongs to Eumys'
- 'Hipparion occidentale belongs to Hipparion'
- 'Hippodon speciosus is recombined as Hipparion speciosum'
- 'Hyaenodon crucians belongs to Hyaenodon'
- 'Hyaenodon cruentus belongs to Hyaenodon'
- 'Hyaenodon horridus belongs to Hyaenodon'
- 'Choeropotamus (Hyopotamus) is replaced by Choeropotamus (Hyopotamus)'
- 'Hyopotamus was reranked as Choeropotamus (Hyopotamus) and belongs to Choeropotamus'
- 'Hyopotamus americanus is recombined as Choeropotamus (Hyopotamus) americanus'
- 'Hyracodon was reranked as Rhinoceros (Hyracodon) and belongs to Rhinoceros'
- 'Ichthyosaurus missouriensis is recombined as Mosasaurus missouriensis'
- 'Ischyromys typus belongs to Ischyromys'
- 'Lepidotus haydeni belongs to Lepidotus'
- 'Lepidotus occidentalis belongs to Lepidotus'
- 'Leptarctus primus belongs to Leptarctus'
- 'Leptauchenia decora belongs to Leptauchenia'
- 'Leptauchenia major belongs to Leptauchenia'
- 'Leptochoerus spectabilis belongs to Leptochoerus'
- 'Leptomeryx evansi belongs to Leptomeryx'
- 'Machairodus primaevus belongs to Machairodus'
- 'Mammut ohioticum is recombined as Mastodon ohioticum'
- 'Manatus antiquus is recombined as Ischyrotherium antiquus'
- 'Megalosaurus (Deinodon) belongs to Megalosaurus'
- 'Merychippus insignis belongs to Merychippus'
- 'Merycodus necatus belongs to Merycodus'
- 'Merycoidodon culbertsonii is recombined as Oreodon culbertsoni'
- 'Mosasaurus maximilliani is a subjective synonym of Mosasaurus missouriensis'
- 'Mylognathus priscus belongs to Mylognathus'
- 'Oreodon gracile is corrected as Oreodon gracilis and belongs to Oreodon'
- 'Oreodon major belongs to Oreodon'
- 'Oreodon priscus is a subjective synonym of Oreodon culbertsoni'
- 'Palaeochoerus probus belongs to Palaeochoerus'
- 'Palaeolagus haydeni belongs to Palaeolagus'
- 'Palaeoscincus costatus belongs to Palaeoscincus'
- 'Palaeotherium bairdii is recombined as Anchitherium bairdii'
- 'Palaeotherium giganteum is a subjective synonym of Titanotherium proutii'
- 'Palaeotherium proutii is recombined as Titanotherium proutii'
- 'Poebrotherium wilsoni belongs to Poebrotherium'
- 'Protomeryx halli belongs to Protomeryx'
- 'Rhinoceros americanus is a subjective synonym of Titanotherium proutii'
- 'Rhinoceros nebraskensis is recombined as Rhinoceros (Hyracodon) nebrascensis'
- 'Rhinoceros occidentalis belongs to Rhinoceros'
- 'Saurocephalus lanciformis belongs to Saurocephalus'
- 'Steneofiber nebrascensis belongs to Steneofiber'
- 'Stylemys nebrascensis is recombined as Testudo nebrascensis'
- 'Thespesius occidentalis belongs to Thespesius'
- 'Trachodon mirabilis belongs to Trachodon'
- 'Trionyx foveatus belongs to Trionyx'
- 'Troodon formosus belongs to Troodon'