Opinions from J. H. Quinn 1955
- 'Anchitheridae was reranked as the subfamily Anchitheriinae and belongs to Equidae'
- 'Anchitherium ultimum is recombined as Archaeohippus ultimus'
- 'Archaeohippus belongs to Anchitheriinae'
- 'Asinus belongs to Equini'
- 'Astrohippus curtivallis belongs to Astrohippus'
- 'Calippini belongs to Equinae'
- 'Calippus anatinus belongs to Calippus'
- 'Calippus martini is recombined as Protohippus martini'
- 'Calippus optimus belongs to Calippus'
- 'Dinohippus belongs to Equini'
- 'Dinohippus subvenus belongs to Dinohippus'
- 'Eoequus belongs to Equini'
- 'Eoequus wilsoni belongs to Eoequus'
- 'Equidae belongs to Perissodactyla'
- 'Equinae belongs to Equidae'
- 'Equini belongs to Equinae'
- 'Equus belongs to Equini'
- 'Equus (Protohippus) was reranked as Protohippus and belongs to Protohippini'
- 'Equus (Protohippus) perditus is recombined as Protohippus perditus'
- 'Equus burchelli is recombined as Hippotigris burchelli'
- 'Equus caballus belongs to Equus'
- 'Equus capensis belongs to Equus' according to Broom 1909
- 'Equus capensis is recombined as Hippotigris capensis'
- 'Equus cumminsii is recombined as Asinus cumminsii'
- 'Equus francisci is recombined as Asinus francisci'
- 'Equus laparensis belongs to Equus'
- 'Equus simplicidens is recombined as Hippotigris simplicidens'
- 'Equus zebra is recombined as Hippotigris zebra'
- 'Griphippus belongs to Calippini'
- 'Hipparion belongs to Hipparionini'
- 'Hipparion (Nannippus) was reranked as Nannippus and belongs to Hipparionini'
- 'Hipparion gratum is recombined as Griphippus gratus'
- 'Hipparionini belongs to Equinae'
- 'Hippidium interpolatum is recombined as Dinohippus interpolatus'
- 'Hippidium spectans is recombined as Pliohippus spectans'
- 'Hippodon belongs to Protohippini'
- 'Hippodon speciosus belongs to Hippodon'
- 'Hippotigris belongs to Equini'
- 'Hippotigris clarendonensis belongs to Hippotigris'
- 'Hippotigris grevyi belongs to Hippotigris' according to Oustalet 1882
- 'Hippotigris grevyi belongs to Hippotigris'
- 'Hippotigris parastylus belongs to Hippotigris'
- 'Hippotigris robustus belongs to Hippotigris' according to Pomel 1853
- 'Hippotigris robustus belongs to Hippotigris'
- 'Hippotigris sellardsi belongs to Hippotigris'
- 'Hippotigris stenonis belongs to Hippotigris'
- 'Hippotigris stenonis belongs to Hippotigris' according to Cocchi 1867
- 'Merychippus belongs to Hipparionini'
- 'Merychippus francisi is recombined as Calippus francisi'
- 'Merychippus gunteri is recombined as Hippodon gunteri'
- 'Merychippus intermontanus is recombined as Pliohippus intermontanus'
- 'Merychippus mirabilis is recombined as Pliohippus mirabilis'
- 'Merychippus vellicans is recombined as Hippodon vellicans'
- 'Miohippus blackbergi is recombined as Archaeohippus blackbergi'
- 'Neohipparion belongs to Hipparionini'
- 'Parahippus barbouri is recombined as Hippodon barbouri'
- 'Parahippus leonensis is recombined as Hippodon leonensis'
- 'Plesippus shoshonensis is recombined as Hippotigris shoshonensis'
- 'Pliohippus belongs to Protohippini'
- 'Pliohippus (Astrohippus) was reranked as Astrohippus and belongs to Calippini'
- 'Pliohippus (Astrohippus) stockii is recombined as Astrohippus stocki'
- 'Pliohippus (Pliohippus) mexicanus is recombined as Asinus mexicanus'
- 'Pliohippus circulus belongs to Pliohippus'
- 'Pliohippus leardi belongs to Pliohippus'
- 'Pliohippus leidyanus is recombined as Dinohippus leidyanus'
- 'Pliohippus osborni is recombined as Hippotigris osborni'
- 'Pliohippus pernix belongs to Pliohippus'
- 'Protohippini belongs to Equinae'
- 'Protohippus (Calippus) was reranked as Calippus and belongs to Calippini'
- 'Protohippus ansae is recombined as Astrohippus ansae'
- 'Protohippus placidus is recombined as Calippus placidus'
- 'Protohippus supremus is recombined as Pliohippus supremus'
- 'Protohippus vetus belongs to Protohippus'