The earliest period of the Mesozoic era. It began about 252 million years ago, following the Permian, the last period of the Palaeozoic era, and extended until about 201 million years ago when it was succeeded by the Jurassic. It was named, by F. von Alberti in 1834, after the sequence of three divisions of strata that he studied in central Germany—Bunter, Muschelkalk, and Keuper. The Triassic rocks are frequently difficult to distinguish from the underlying Permian strata and the term New Red Sandstone is often applied to rocks of the Permo-Triassic. During the period marine animals diversified: molluscs were the dominant invertebrates—ammonites were abundant and bivalves replaced the declining brachiopods. Reptiles were the dominant vertebrates and included turtles, phytosaurs, dinosaurs, and the marine ichthyosaurs.