Note: This item is currently under review in 'proposed content' section
Giant viruses are a recently discovered (2003) group of viruses, some of which have a genome larger than that of many bacteria. Their evolutionary history is a mystery.
“The discovery of giant viruses blurred the sharp division between viruses and cellular life. Giant virus genomes encode proteins considered as signatures of cellular organisms, particularly translation system components, prompting hypotheses that these viruses derived from a fourth domain of cellular life.”
Note: Another group of virus-like entities called 'virophages' predate the Giant Viruses. Their evolutionary origin is also unknown.