Rhinoceros belong to a mammalian order called odd-toed ungulates that also include horses and tapirs. They are found in Africa and Asia. Until recently, evidence suggested that throughout their evolutionary history, gammaretroviruses such as Murine leukemia virus had not colonized their genomes, unlike most other mammalian orders.
Click here for original story, African rhinos share retroviruses not found in Asian rhinos or other related species
Source: Phys.org