The Tethys Ocean, also called the Tethys Sea or the Neo-Tethys, was a prehistoric ocean during much of the Mesozoic Era and early-mid Cenozoic Era. It was the predecessor to the modern Indian Ocean, the Mediterranean Sea, and the Eurasian inland marine basins.
Vast regions of Europe and west-central Asia were still covered by a contiguous Tethys at the start of the Eocene (top image), but by the Oligocene, most of this had dried out (bottom image), and the Tethys was almost entirely divided into the Indian Ocean, Mediterranean and Paratethys.
Geologist Eduard Suess in 1869
The Mesozoic Era is the second-to-last era of Earth's geological history, lasting from about 252 to 66 million years ago, comprising the Triassic, Jurassic and Cretaceous Periods. It is characterized by the dominance of gymnosperms and of archosaurian reptiles, such as the dinosaurs; a hot greenhouse climate; and the tectonic break-up of Pangaea. The Mesozoic is the middle of the three eras since complex life evolved: the Paleozoic, the Mesozoic, and the Cenozoic.
Plateosaurus (a prosauropod)
Sericipterus
Stegosaurus
Tylosaurus (a mosasaur) hunting Xiphactinus