Avannacystis

Avannacystis is a genus of extinct, spherical microorganism from the Middle Cambrian Henson Gletscher Formation of North Greenland, first found in 2006 and formally described in 2026. Its single species, A. polaris, forms vesicles 20 to 120 micrometers across, usually with a single surface dimple, and colonized the shells of the small shelly fossil Tesella in what appears to have been a parasitic or commensal relationship. Its true biological identity is unresolved, with researchers unable to rule out a fungal, algal or sulfur oxidizing bacterial origin.