the root (no rank)
Viruses (domain)
retroid viruses (subkingdom)
Retroviridae (family)
Orthoretrovirinae (subfamily)
Betaretrovirus (genus)
[hide inferior taxa]
human MMTV-related defective virus (species)
human retrovirus 5 (species)
Mason-Pfizer monkey virus (species)
mouse mammary tumor virus (species)
ovine enzootic nasal tumour virus (species)
ovine pulmonary adenocarcinoma virus (species)
squirrel monkey retrovirus (species)