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 Alpharetrovirus 1 Avian carcinoma Mill Hill virus 2 2 Avian leukosis virusᵀ 3 Avian myeloblastosis virus 4 Avian myelocytomatosis virus 29 5 Avian sarcoma virus CT10 6 Fujinami sarcoma virus 7 Rous sarcoma virus 8 UR2 sarcoma virus 9 Y73 sarcoma virus