Opinions from T. Fremd 1994
- 'Anchippus brevidens is a subjective synonym of Merychippus relictus'
- 'Anchitherium equiceps is recombined as Miohippus equiceps'
- 'Anchitherium praestans is recombined as Kalobatippus praestans'
- 'Archaelurus debilis is recombined as Nimravus debilis'
- 'Coloreodon macrocephalus is recombined as Agriochoerus macrocephalus'
- 'Cynodictis oregonensis is recombined as Cormocyon oregonensis'
- 'Cynodictis oregonensis is recombined as Nothocyon oregonensis' according to Hall and Martin 1930
- 'Desmatippus belongs to Equidae'
- 'Desmatippus crenidens belongs to Desmatippus'
- 'Diceratherium nanum is a subjective synonym of Diceratherium armatum'
- 'Eporeodon leptacanthus is a subjective synonym of Merycochoerus occidentalis'
- 'Eucrotaphus pacificus is a subjective synonym of Merycochoerus occidentalis'
- 'Eucrotaphus trigonocephalus belongs to Eucrotaphus'
- 'Gomphotherium cameloides is recombined as Oxydactylus cameloides'
- 'Gomphotherium cameloides is recombined as Miolabis cameloides' according to Stevens 1977
- 'Gomphotherium cameloides is recombined as Miolabis cameloides' according to McKenna 1966
- 'Hippotherium isonesum is a subjective synonym of Merychippus seversus'
- 'Hoplophoneus platycopis is recombined as Nimravus platycopis'
- 'Ictiocyon crassivultus is recombined as Oligobunis crassivultus'
- 'Machaerodus cerebralis is recombined as Eusmilus cerebralis'
- 'Machaerodus strigidens is recombined as Hoplophoneus strigidens'
- 'Meniscomys liolophus is recombined as Haplomys liolophus'
- 'Oreodon major is recombined as Mesoreodon major'
- 'Oreodon occidentalis is recombined as Merycochoerus occidentalis'
- 'Oreodon occidentalis is recombined as Eucrotaphus occidentalis' according to Cope 1879
- 'Oreodon superbus is recombined as Promerycochoerus superbus'
- 'Pogonodon davisi is recombined as Nimravus davisi'
- 'Protohippus avus is recombined as Desmatippus avus'
- 'Pseudogenetochoerus covensis is a subjective synonym of Eucrotaphus trigonocephalus'
- 'Rhinoceros hesperius is a subjective synonym of Diceratherium annectens'
- 'Rhinoceros oregonensis is a subjective synonym of Diceratherium armatum'
- 'Rhinoceros pacificus is a subjective synonym of Diceratherium armatum'
- 'Steneofiber gradatus is recombined as Capacikala gradatus'
- 'Temnocyon coryphaeus is recombined as Mesocyon coryphaeus'
- 'Temnocyon josephi is recombined as Paraenhydrocyon josephi'
- 'Thinohyus (Bothrolabis) osmonti is recombined as Perchoerus osmonti'
- 'Thinohyus lentus is recombined as Perchoerus lentus'