With the benefit of newly collected material, primitive equoids are analysed cladistically to determine the detailed relationships of the families Equidae and Palaeotheriidae. The most primitive equid is shown to bePliolophus. Cymbalophus cuniculusand‘Hyracotherium’ sandraeare closely related stem equoids. The Pachynolophidae are not equoids, but most closely related to the primitive tapiromorph family Isectolophidae.Hallensiais sister to these two and therefore also not an equoid.Hyracotheriumis restricted to the type speciesH. leporinumOwen, part of whose lower dentition is made known for the first time. It is closest to a restricted genusPropachynolophuswithin the family Palaeotheriidae. The original concept ofPropachynolophusis polyphyletic. Using the cladogram, newly extended stratigraphic ranges and palaeogeography, an attempt is made to reconstruct the very early speciation and biogeographical history of the group.‘Cymbalophus’ hookeriGodinot is recombined in the genusPachynolophus and ‘H.’ pernixinPliolophus. Hallensia louisisp. nov. and Propachynolophus level sp. nov. ar