Opinions from L. T. Holbrook 1999
- 'Amynodon belongs to Amynodontidae'
- 'Amynodontidae belongs to Rhinocerotoidea'
- 'Cardiolophus belongs to Perissodactyla'
- 'Ceratomorpha was reranked as a infraorder and belongs to Tapiromorpha'
- 'Chalicotheriidae belongs to Chalicotherioidea'
- 'Chalicotherioidea belongs to Perissodactyla'
- 'Colodon belongs to Helaletidae'
- 'Colodon hancocki is recombined as Plesiocolopirus hancocki'
- 'Deperetella belongs to Deperetellidae'
- 'Deperetellidae belongs to Tapiroidea'
- 'Eomoropidae belongs to Chalicotherioidea'
- 'Eomoropus belongs to Eomoropidae'
- 'Forstercooperia belongs to Rhinocerotoidea'
- 'Helaletes belongs to Helaletidae'
- 'Helaletidae belongs to Tapiroidea'
- 'Heptodon belongs to Heptodontidae'
- 'Heptodontidae belongs to Tapiroidea'
- 'Homogalax belongs to Perissodactyla'
- 'Hyrachyidae belongs to Rhinocerotoidea'
- 'Hyrachyus belongs to Hyrachyidae'
- 'Hyracodon belongs to Hyracodontidae'
- 'Hyracodontidae belongs to Rhinocerotoidea'
- 'Indricotheriidae belongs to Rhinocerotoidea'
- 'Isectolophidae belongs to Tapiromorpha'
- 'Isectolophus belongs to Isectolophidae'
- 'Juxia belongs to Rhinocerotoidea'
- 'Lophialetes belongs to Lophialetidae'
- 'Lophialetidae belongs to Tapiroidea'
- 'Moropus belongs to Chalicotheriidae'
- 'Paraceratherium belongs to Indricotheriidae'
- 'Plesiocolopirus belongs to Helaletidae'
- 'Protapirus belongs to Tapiridae'
- 'Rhinocerotidae belongs to Rhinocerotoidea'
- 'Rhinocerotoidea belongs to Ceratomorpha'
- 'Rostriamynodon belongs to Amynodontidae'
- 'Schlosseria belongs to Lophialetidae'
- 'Subhyracodon belongs to Rhinocerotidae'
- 'Taperidae is corrected as Tapiridae and belongs to Tapiroidea'
- 'Tapiroidea belongs to Ceratomorpha'
- 'Tapiromorpha belongs to Perissodactyla'
- 'Tapirus belongs to Tapiridae'
- 'Teletaceras belongs to Rhinocerotidae'
- 'Trigonias belongs to Rhinocerotidae'
- 'Triplopus belongs to Hyracodontidae'
- 'Uintaceras belongs to Rhinocerotidae'