The genome of "Pithovirus" has 467 different genes, more than a typical virus but far less than "Pandoravirus". Its genome is much less densely packed than any other known virus. Two-thirds of its proteins are unlike those of other viruses. Despite the physical similarity with "Pandoravirus", the "Pithovirus" genome sequence shows that it is barely related to that virus. It more closely resembles members of some other virus families. These families all contain large icosahedral viruses with DNA genomes. The "Pithovirus" genome has 36% GC-content, similar to the "Megaviridae", in contrast to greater than 61% for pandoraviruses.