Natura - nature
   actualia - actual entities
     Mundus Plinius - physical world
       naturalia - natural bodies
         [crown] Clade Biota Wagner 2004 [Wiemann, de Queiroz, Rowe, Planavsky, Anderson, Gogarten, Turner & Gauthier 2020]
           ?"viruses"
             Order Ortervirales
               Family Retroviridae
                 Subfamily Orthoretrovirinae
                   1.1 Genus Epsilonretrovirus
                   1.2 Genus Gammaretrovirus
                   2.1 Genus Deltaretrovirus
                   2.2.1.1 Genus Alpharetrovirus
                   2.2.1.2 Genus Betaretrovirus
                   2.2.2 Genus Lentivirus