The Triassic began 252 million years ago, and it ended 201 million years ago. It was the period when the first dinosaurs appeared. New calcareous algal and coral reefs were built. The clams got a higher diversity and the brachiopods lost this. Many crinoids lived on the reefs. In the water, ammonites and belemnites swam. On land, conifers and other seed plants grew together with ferns. These areas were dominated by different reptiles like early dinosaurs and mammal-like reptiles. In the seas, different marine reptiles emerged. The climate was hot and dry. At the end, there was another big mass extinction.
On the picture, you can see sponges, modern corals, crinoids and other kinds of sea life on the seafloor. Above them, ammonites, belemnites, fishes, and marine reptiles like Nothosaurus and Cymbospondylus are swimming. In the background, you can see a forest with ferns, cycadeens, conifers, and the clubmoss Pleuromeia. Further, there are different reptiles like Cynognathus, Pappochelys and the dinosaur Plateosaurus in the forest. You can also see the huge amphibian Mastodonsaurus and the early pterosaur Peteinosaurus.