Late Triassic | norian age
The Norian age is the second stage of the three to occur during the duration of the triassic mass extinction. This stage developed about 217 to 204 million years ago. This stage comes after the Carnian stage, and is known for its rising populations of mesozoic organisms as well as the decline in populations of previous species that had once played important roles in the environment. This stage identifies with its own species of ammonoid index fossils, which is how it differs from the preceding Carnian stage. In this stage, fossils and evidence of Cyrtopleurites bicrenatus are found in these different areas of the world, which seem to be more complex and advanced than those in the preceding stage of the era. Many species alive during the Norian age that eventually became extinct lived either in the Tethys-Panthalassan reef province, or the West Pangean reef province. in the Tethys-Panthalassan province, species saw considerable amounts of populations becoming extinct here. Species such as the sphinctozoid as well as other species began dying out, and by the end of the Norian stage, about 90% of these species evolved and remained in the area. Further evidence shows that scientists discovered major rises in sea level towards later years of the stage, in which new taxa came into play.