Natura - nature
   actualia - actual entities
     Mundus Plinius - physical world
       naturalia - natural bodies
         Biota Wagner 2004 [Wiemann, de Queiroz, Rowe, Planavsky, Anderson, Gogarten, Turner & Gauthier 2020]
           ?"viruses"
             Order Ortervirales
               Family Retroviridae
                 1 Subfamily Orthoretrovirinae
                 2 Subfamily Spumaretrovirinae