Any of a diverse group of eukaryotic DNA viruses that have unusually large capsids, comparable in size with small bacteria, and contain large genomes, ranging in size from 100 kbp to 2.5 Mbp. Among the largest are Mimivirus and the related Megavirus, discovered in 2011, which measure 600 and 640 nm in diameter respectively and have a genome size of roughly 1.2 Mbp. However, these are outstripped by the pandoraviruses, which are roughly 1000 nm long, and Pithovirus, which at 1500 nm long is the largest known virus. All four infect amoebas. Other NCLDVs include the phycodnaviruses (which infect algae), poxviruses, African swine fever virus, and iridoviruses, all of which infect metazoan animals. All are equipped with most of the genes needed for replication of their DNA and virion assembly: they either replicate in the cytoplasm of their host cells or pass to the cytoplasm after beginning their replication in the nucleus. Some regard their large genomes as evidence that NCLDVs have undergone reductive evolution from more complex cellular predecessors, and may represent ancestors of cellular life forms, whereas an alternative explanation is that they have acquired many of their genes by accretion from their hosts. In 2013 a new viral order, the Megavirales, was proposed to accommodate the NCLDVs on the basis of their shared genes, virion structure, and mode of replication. However, the relationship of NCLDVs to the other domains of life is contentious; for example, it has been proposed that the giant amoebal viruses are true microbes and represent a new domain of life.