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,
Gulf Keystone Petroleum is notably one of the largest Super Giant oilfields discovered in the last 50 years. Shaikan was declared a commercial discovery on August 1, 2012 following a five-well appraisal program. Initially independent estimates place the gross oil-in-place (OIP) volume at 13.7 billion barrels (P50) potentially making it one of the largest oilfields discovered in Iraqi Kurdistan. The oilfield covers an area of some , and comprises a series of limestone reservoirs stacked upon each other. These reservoirs encompass a very long period of geological time, from the Cretaceous which ended some 65 million years ago to the Triassic, which began