The Iapatus ocean existed during the Ordovician period of the Paleozoic Era. The Ipatus ocean supported both shallow water and deep water ecosystems. All fossil organisms found in the Iapatus ocean sediments and marine. (Benthic or Pelagic). Many Genera of organisms are known from sediments formed from the Iapatus ocean. The Trilobite species of Pseudogygites Lantimarginatus, Isotelus Gigas, Triarthrus Eotoni and Triarthrus Spinosus all lived in the Iapatus ocean. Pseudogygites fossil exoskeletons are often found in excavation sites of the Iapatus ocean sediments. Larger pygidiums and full exoskeletons are found in thicker shale from the deep water environments of the Iapatus ocean. Smaller Pseudogygites pygidiums and full exoskeletons are found in thinner shale from the shallow water reef environments of the Iapatus ocean. This may indicate that, like its modern-day relative, the horseshoe crab, Pseuodogygites individuals lived for the first few months or years of their lives in the shallow water reef ecosystems before migrating to deeper water environments, remaining there for the rest of their lifecycle.