Parakaryon myojinensis
Parakaryon myojinensis, also known as the Myojin parakaryote, is a highly unusual species of single-celled organism known from a single specimen, described in 2012. It has features of both prokaryotes and eukaryotes but is apparently distinct from either group, making it unique among organisms so far discovered. It is the sole species in the genus Parakaryon. Etymology. The generic name "Parakaryon" comes from Greek παρά ("pará", beside) and κάρυον ("káryon", kernel, nucleus), and reflects its distinction from eukaryotes and prokaryotes. The specific name "myojinensis" reflects the locality where the only sample was collected; from the bristle of  a scale worm collected from hydrothermal vents at Myōjin Knoll (明神海丘, 32°06.2′N, 139°52.1′E) 1240 m deep in the Pacific Ocean, near Aogashima island, southeast of the Japanese archipelago. Structure. "Parakaryon myojinensis" has some structural features unique to eukaryotes, some features unique to prokaryotes, and some features different to both. The table below details these structures, with matching traits coloured beige. Classification. It is not clear whether "P. myojinensis" can be classified as a eukaryote or a prokaryote, the two categories to which all other cellular life belongs. Excluding viruses, which are non-cellular and often distinguished  from cellular life, and excluding several fossils that contain disputed evidence of ancient life (nanobacteria, nanobes), "P. myojinensis" is the only organism to have a completely unknown position in the tree of life. Adding to the difficulties of classification, only one instance of this organism has been discovered to date, and so scientists have been unable to study it further.