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
                   Genus Betaretrovirus
                     1 Jaagsiekte sheep retrovirus
                     2 Langur virus
                     3 Mason-Pfizer monkey virus
                     4 Mouse mammary tumor virusᵀ
                     5 Squirrel monkey retrovirus