Late Triassic | rhaetian age
The Rhaetian age is the final stage of the Triassic era's mass extinction. The Rhaetian age succeeds the Norian stage, and is the step before the eventual cretaceous era mass extinction. This stage of the Triassic is known for its extinction of marine reptiles, such as nothosaurs and shashtosaurs with the ichthyosaurs, similar to today's dolphin. This stage was concluded with the disappearance of many species that removed types of plankton from the face of the earth, as well as some organisms known for reef-building, and the pelagic conodonts. In addition to these species that became extinct, the straight-shelled nautoloids, placodonts, bivalves and many types of reptiles did not survive through this stage.