Opinions from M. W. Colbert and R. M. Schoch 1998
- 'Cardiolophus belongs to Isectolophidae'
- 'Chasmotherium is a subjective synonym of Hyrachyus'
- 'Chasmotheriodes is a subjective synonym of Desmatotherium'
- 'Colodon belongs to Tapiroidea'
- 'Colodon dakotensis is a subjective synonym of Colodon occidentalis'
- 'Colodon hancocki is recombined as Protapirus hancocki'
- 'Colodon luxatus is a subjective synonym of Colodon occidentalis'
- 'Colodon procuspidatus is a subjective synonym of Colodon occidentalis'
- 'Colonoceras is a subjective synonym of Hyrachyus'
- 'Colonoceras agrestis is a subjective synonym of Hyrachyus modestus'
- 'Desmatotherium belongs to Ceratomorpha'
- 'Desmatotherium guyotii is a subjective synonym of Desmatotherium intermedius'
- 'Desmatotherium kayi is recombined as Colodon kayi'
- 'Desmatotherium woodi is recombined as Colodon woodi'
- 'Dilophodon belongs to Ceratomorpha'
- 'Dilophodon minusculus belongs to Dilophodon'
- 'Ephyrachyus is a subjective synonym of Hyrachyus'
- 'Ephyrachyus cristalophus is a subjective synonym of Hyrachyus modestus'
- 'Fouchia belongs to Ceratomorpha'
- 'Helaletes belongs to Tapiroidea'
- 'Helaletes boops is a subjective synonym of Helaletes nanus'
- 'Helaletes latidens is recombined as Isectolophus latidens'
- 'Heptodon belongs to Ceratomorpha'
- 'Heptodon brownorum is a subjective synonym of Heptodon posticus'
- 'Heteraletes belongs to Tapiroidea'
- 'Heteraletes leotanus belongs to Heteraletes'
- 'Homogalax belongs to Isectolophidae'
- 'Homogalax bridgerensis is a subjective synonym of Isectolophus latidens'
- 'Homogalax uintensis is a subjective synonym of Isectolophus annectens'
- 'Hyrachyus belongs to Rhinocerotoidea'
- 'Hyrachyus agrarius is a subjective synonym of Hyrachyus modestus'
- 'Hyrachyus agrestis is a subjective synonym of Hyrachyus modestus'
- 'Hyrachyus crassidens is a subjective synonym of Hyrachyus modestus'
- 'Hyrachyus eximius belongs to Hyrachyus'
- 'Hyrachyus hypostylus is a subjective synonym of Hyrachyus eximius'
- 'Hyrachyus imperialis is a subjective synonym of Hyrachyus eximius'
- 'Hyrachyus intermedius is recombined as Desmatotherium intermedius'
- 'Hyrachyus princeps is a subjective synonym of Hyrachyus eximius'
- 'Isectolophus belongs to Isectolophidae'
- 'Isectolophus scotti is a subjective synonym of Isectolophus annectens'
- 'Lophiodon affinis is recombined as Hyrachyus affinis'
- 'Lophiodon bairdianus is a subjective synonym of Hyrachyus modestus'
- 'Lophiodon calciculus is recombined as Heptodon calciculus'
- 'Lophiodon modestus is recombined as Hyrachyus modestus'
- 'Lophiodon nanus is recombined as Helaletes nanus'
- 'Lophiodon occidentalis is recombined as Colodon occidentalis'
- 'Lophiodon validus is recombined as Tapiravus validus'
- 'Lophiodon ventorum is a subjective synonym of Heptodon calciculus'
- 'Mesohippus longipes is a subjective synonym of Colodon occidentalis'
- 'Metahyrachyus is a subjective synonym of Hyrachyus'
- 'Metahyrachyus bicornutus is recombined as Hyrachyus bicornutus'
- 'Metahyrachyus troxelli is a subjective synonym of Hyrachyus eximius'
- 'Miotapirus belongs to Tapiridae'
- 'Pachynolophus posticus is recombined as Heptodon posticus'
- 'Paleomoropus belongs to Moropomorpha'
- 'Parisectolophus is a subjective synonym of Isectolophus'
- 'Plesiocolopirus is a subjective synonym of Protapirus'
- 'Protapirus belongs to Tapiridae'
- 'Schizolophodon is a subjective synonym of Isectolophus'
- 'Schizolophodon cuspidens is a subjective synonym of Isectolophus annectens'
- 'Schizotheriodes belongs to Moropomorpha'
- 'Schizotheriodes jackwilsoni is a subjective synonym of Toxotherium hunteri'
- 'Selenaletes belongs to Ceratomorpha'
- 'Systemodon is a subjective synonym of Homogalax'
- 'Systemodon primaevus is a subjective synonym of Homogalax protapirinus'
- 'Systemodon protapirinum is recombined as Homogalax protapirinus'
- 'Systemodon semihians is recombined as Cardiolophus semihians'
- 'Tanyops is a subjective synonym of Protapirus'
- 'Tanyops undans is a subjective synonym of Protapirus obliquidens'
- 'Tapiravus belongs to Tapiridae'
- 'Tapiravus is a nomen dubium' according to Simpson 1945
- 'Tapiravus rarus is a nomen dubium'
- 'Tapiravus rarus belongs to Tapiravus' according to Marsh 1877
- 'Tapirus belongs to Tapiridae'
- 'Tapirus copei is a subjective synonym of Tapirus haysii'
- 'Tapirus excelsus is a subjective synonym of Tapirus veroensis'
- 'Tapirus haysii belongs to Tapirus'
- 'Tapirus merriami belongs to Tapirus'
- 'Toxotherium belongs to Rhinocerotoidea'
- 'Toxotherium woodi is a subjective synonym of Toxotherium hunteri'