Ku dhammee weedhan soo socda: Noocyada ugu horeeya ee la magacaabay waxaa laga helay Miocene Mascall Fauna ee Cottonwood Creek, Oregon. Noocan waxaa lagu magacaabaa "Anchitherium ultimus" waxaana lagu tilmaamay 1886 kii aqoonyahan caan ah, E. D. Cope inta lagu gudajiray dagaalkii lafaha. Intii lagu guda jiray daraasadda 1906 ee ku saabsan dhismaha Mascall equids, J. Gidley wuxuu u guuray nooc cusub oo uu ugu magac daray "Archaeohippus". Isku ekaanshaha xoogga leh ee astaamaha waxay keentay in hiddaha loo tixgeliyo nooc hoosaad ah "Parahippus" oo uu qoray W. D. Matthew 1932. Marka la barbardhigo aragtida "Archaeohippus" waxaa dib u cusbooneysiiyay D.F. Bode 1933, iyo "A. ultimus", wuxuu ku daray "A. mourningi" iyo "A. penultimus". "Archaeohippus" waxay ku baahsanayd Waqooyiga Ameerika oo dhan. Marka laga soo tago Florida iyo Oregon, waxaa sidoo kale laga helay noocyo kale oo ku nool Koonfurta Saskatchewan, Kanada. Dhamaadka kale ee kala duwanaanshaheeda "Archaeohippus" ayaa laga helay koonfurta ilaa Miocene Gaillard Cut ee deegaanka
dhulka hoostiisa mara ee hore ee Panama. ""Archaeohippus" stenolophus", oo laga yaqaan Oligocene deposit ee Saskatchewan, kuma eka "Archaeohippus", iyo "A. minimus" waa isku dhafan laba taxan, sida uu xusay Osborn (1918), oo leh P3-M1 oo ka tirsan "A. ultimus" iyo molar iyo premolar oo ka tirsan mid weyn, oo ka soo jeeda equid. "Archaeohippus mannulus" iyo "Arachaeohippus blackbergi" ayaa laga helay Florida, gaar ahaan Thomas Farm Site.