The recently proposed transfer of four rickettsias from the genera Haemobartonella and Eperythrozoon to the genus Mycoplasma with the Candidatus status is herein revised. This is because the Candidatus designation is for new, incompletely described taxa, in order to give them a provisional status. Thus, 'Candidatus Mycoplasma haemofelis' is revised to Mycoplasma haemofelis comb. nov., nom. nov., 'Candidatus Mycoplasma haemomuris' is revised to Mycoplasma haemomuris comb. nov., nom. nov., 'Candidatus Mycoplasma haemosuis' is revised to Mycoplasma haemosuis comb. nov., nom. nov. and 'Candidatus Mycoplasma wenyonii' is revised to Mycoplasma wenyonii comb. nov.