Long-necked and short-necked plesiosaurs “flew” through Mesozoic seas
Plesiosaurs were Mesozoic marine reptiles of Sauropterygia, appearing by the latest Triassic (possibly Rhaetian, about 203 million years ago). Broad bodies, short tails, and four muscular flippers powered underwater flight. They are not dinosaurs, though often sold as such in popular media.
Plesiosaurs were marine reptiles of the group Sauropterygia. They appeared at the very end of the Triassic, perhaps during the Rhaetian, roughly 203 million years back, flourished especially in the Jurassic, and vanished in the extinction at the end of the Cretaceous about 66 million years ago. They swam in oceans worldwide, and some lived at least partly in fresh water. Like ichthyosaurs and mosasaurs, they were not dinosaurs.
The body was broad and flat with a short tail, and the four limbs had become long flippers driven by powerful muscles anchored to wide bony plates of the shoulder and hip girdles. They beat these flippers in a flying motion. Plesiosaurs breathed air and gave birth to live young, and there are signs they were warm-blooded. Two body plans recur. Plesiosauromorphs had long, sometimes extremely long, necks and small heads and were fairly slow hunters of small animals; pliosauromorphs had short necks and big heads and were fast apex predators of large prey. Because some long-necked lineages turn out to include short-necked members and vice versa, these descriptive terms have partly replaced the old two-suborder scheme.
Their bones were among the earliest extinct-reptile fossils ever recognised. In 1605 Richard Verstegen of Antwerp illustrated plesiosaur vertebrae, thinking them fish and taking them as proof that Britain was once joined to the continent. Edward Lhuyd pictured more vertebrae in 1699, also as fish. In 1719 William Stukeley described a partial skeleton brought to him by Robert Darwin of Elston, great-grandfather of Charles Darwin. The slab had come from a Fulbeck quarry and been set into a watering-hole slope, then shown in a vicarage as a sinner drowned in the Flood. Now in the Natural History Museum, it is the earliest roughly complete fossil reptile skeleton held by a museum.
Scientists grasped how distinctive the group was in the early nineteenth century. Plesiosaurus was named in 1821, the order was established in 1835, and more than a hundred valid species have since been described, with finds accelerating this century.
Source: Plesiosaur
