Equidae Gray, 1821
Merychippus brevidontus
Merychippus calamarius
Merychippus californicus
Merychippus coloradense
Merychippus eohipparion
Merychippus eoplacidus
Merychippus goorisi
Merychippus gunteri
Merychippus insignis
Merychippus intermontanus
Merychippus isonesus
Merychippus paniensis Rayment, 1874
Merychippus patrusus
Merychippus primus
Merychippus proparvulus
Merychippus quartus
Merychippus quintus
Merychippus relictus
Merychippus republicanus
Merychippus shirleyae
Merychippus sphenodus
Merychippus stevensi
Merychippus sumani