Dinosaurs evolved partway through the Triassic period of the Mesozoic era, around 230 Ma (million years ago). At that time, the earth had one supercontinental landmass, called Pangaea, of which Europe was a part. So it remained throughout the Triassic. By the start of the Jurassic period, some 30 million years later, the supercontinent began to split into Laurasia and Gondwana. The largest inlet from Panthalassa, the superocean that surrounded Pangaea, was called the Tethys Ocean, and as this inlet cut deeper into the supercontinent, much of Europe was flooded.