joining together different families and orders were created over time based on increasing evidence of deeper evolutionary relations. Consequently, in 2016, the ICTV began to consider establishing ranks higher than order as well as how the Baltimore groups would be treated among higher taxa. In two votes in 2018 and 2019, a 15-rank system ranging from realm to species was established by the ICTV. As part of this, the Baltimore groups for RNA viruses and RT viruses were incorporated into formal taxa. In 2018, the realm Riboviria was established and initially included the three RNA virus groups. A year later, Riboviria was expanded to also include both RT groups. Within the realm, RT viruses are included in the kingdom Pararnavirae and RNA viruses in the kingdom Orthornavirae. Furthermore, the three Baltimore groups for RNA viruses are used as defining characteristics of the phyla in Orthornavirae. Unlike RNA viruses and RT viruses, DNA viruses have not been united under a single realm but are instead dispersed across four realms and various taxa that are not assigned to a realm. The realms Adnaviria and Duplodnaviria exclusively contains dsDNA viruses, Monodnaviria primarily contains ssDNA viruses but also contains dsDNA viruses, and Varidnaviria exclusively contains dsDNA viruses, although some proposed members of Varidnaviria, namely the family Finnlakeviridae, are ssDNA viruses. Explanatory notes References Citations General bibliography Systems of virus taxonomy Viruses