The World Register of Marine Species (WoRMS) provides data on the taxonomy of I. islandicus :
Species: I. islandicus (also in this genus: I. hospitalis, I. pacificus)
Tim Friend describes a presentation by German microbiologist Karl Otto Stetter at a conference in Yellowstone National Park (another hot spot of extremophile discoveries), during which Stetter talked about research on N. equitans, I. islandicus as well as the symbiotic (or parasitic) nanoarchaea-ignicoccus relationship:
Using the two-person research submersible Geo, samples were taken of sandy sediment and vent fluids at temperature around 90 degrees C [at the Kolbeinsey Ridge]. Black smoker samples obtained during a dive made on the submersible Alvin at a vent in in the Pacific also were analyzed. Initially, the samples from the mid-Atlantic ridge [Kolbeinsey Ridge] revealed a new genus and species of archaea, which Stetter named Ignicoccus islandicus. Electron microscopy photos taken at Stetter's lab of an additional Ignicoccus isolate revealed tiny strange spheres attached to its surface. This was shocking. No such thing had been seen on archaea. By culturing the organisms together Stetter was able to isolate Nanoarchaea then look for segments of its RNA. It does not possess the similar ribosomal RNA signature of other archaea. Tim Friend, 2007 .
Keywords: microbiology, nanobiology, hyperthermophile, crenarchaeon, nomenclature, taxonomy, history.
References and more to explore
 WoRMS taxon details: Ignicoccus islandicus Huber, Burggraf, Mayer, Wyschkony, Rachel & Stetter, 2000:
 Tim Friend: The Third Domain. The Untold Story of Archaea and the Future of Biotechnology. Joseph Henry Press, Washington, D.C., 2007; pages 121 to 124.