Plesiosauria Plesiosauria The Plesiosauria (; Greek: πλησίος, "plesios", meaning "near to" and "sauros", meaning "lizard") or plesiosaurs are an order or clade of Mesozoic marine reptiles (marine Sauropsida), belonging to the Sauropterygia. Plesiosaurs first appeared in the latest Triassic Period, possibly in the Rhaetian stage, about 203 million years ago. They became especially common during the Jurassic Period, thriving until their disappearance due to the Cretaceous–Paleogene extinction event at the end of the Cretaceous Period, about 66 million years ago. They had a worldwide oceanic distribution. Plesiosaurs were among the first fossil reptiles discovered. In the beginning of the nineteenth century,
Angola Basin by gravity spreading and increased sediment loading, major factors which act upon the Angola Basin. In the basin this tectonic mechanism is attributed to three periods of high strain that occurred at approximately 96, 28, and 10 million years ago, and the most recent high strain activity is still ongoing. These high strain rates lasted anywhere from 15 to 36 million years while rafting itself lasted from 7-10 million years. The formation of the Angola Basin can be divided into three phases of rifting which took place from approximately 145-113 million years ago from the Jurassic to the Cretaceous. Initial