Opinions from H. E. Wood 1934
- 'Chasmotheroides belongs to '
- 'Ephyrachyus belongs to '
- 'Ephyrachyus cristalophus belongs to Ephyrachyus'
- 'Helaletes belongs to Tapiroidea'
- 'Helaletes is a subjective synonym of Hyrachyus' according to Cope 1873
- 'Helaletes belongs to Tapiroidea' according to Marsh 1872
- 'Helaletes boops belongs to Helaletes'
- 'Hyrachyus agrarius is a subjective synonym of Hyrachyus modestus'
- 'Hyrachyus agrestis is a subjective synonym of Hyrachyus modestus'
- 'Hyrachyus crassidens is a nomen dubium'
- 'Hyrachyus douglassi belongs to Hyrachyus'
- 'Hyrachyus eximius belongs to Hyrachyus'
- 'Hyrachyus grande is corrected as Hyrachyus grandis and belongs to Hyrachyus'
- 'Hyrachyus grande is corrected as Hyrachyus grandis and belongs to Hyrachyus' according to Hay 1930
- 'Hyrachyus hypostylus belongs to Hyrachyus'
- 'Hyrachyus imperialis is a subjective synonym of Hyrachyus princeps'
- 'Hyrachyus implicatus is recombined as Ephyrachyus implicatus'
- 'Hyrachyus intermedius is recombined as Chasmotheroides intermedius'
- 'Hyrachyus obliquidens is recombined as Prothyracodon obliquidens'
- 'Hyrachyus paradoxus is a nomen dubium'
- 'Hyrachyus priscus is replaced by Hyrachyus douglassi'
- 'Hyrachyus singularis is recombined as Heptodon singularis'
- 'Hyrachyus singularis is recombined as Heptodon singularis' according to Matthew 1899
- 'Hyrachyus singularis is recombined as Heptodon singularis' according to Cope 1887
- 'Hyrachyus singularis is recombined as Pachynolophus singularis' according to Cope 1881
- 'Lophiodon affinis is recombined as Hyrachyus affinis'
- 'Lophiodon bairdianus is a subjective synonym of Hyrachyus modestus'
- 'Lophiodon bairdianus is a subjective synonym of Hyrachyus eximius' according to Marsh 1899
- 'Lophiodon modestus is recombined as Hyrachyus modestus'
- 'Lophiodon modestus is recombined as Hyrachyus modestus' according to Leidy 1871
- 'Lophiodon nanus is recombined as Helaletes nanus'
- 'Lophiodon pumilus is recombined as Helohippus pumilus' according to Matthew 1899
- 'Lophiodon pumilus is recombined as Hyrachyus pumilus' according to Leidy 1872
- 'Lophiodon pumilus is recombined as Helaletes pumilus'
- 'Lophiodon pumilus is recombined as Pachynolophus pumilus' according to Roger 1896
- 'Metahyrachyus troxelli belongs to Metahyrachyus'
- 'Systemodon is a subjective synonym of Hyracotherium'