1) Archosaur 2) Archosaurian 3) Archosaurian reptile 4) Plesiosaurus 1) Plesiosaurus 
• (n.) One of the Plesiosauria.
any of a group of long-necked marine reptiles found as fossils from the Late Triassic Period into the Late Cretaceous Period (215 million to 80 ... [5 related articles]
(pronounced plee-zee-oh-SAWRS) Plesiosaurs meaning near lizard) were flippered marine reptiles from the Mesozoic Era - they were not dinosaurs. Plesiosaurs are divided into two groups: the Plesiosauroids with long, snake-like necks, tiny heads, and wide bodies, and the Pliosauroids , which had large heads with very strong jaws and short necks. Some...
Ple'si·o·saur noun (Paleon.) One of the Plesiosauria. 
[n] - extinct marine reptile with a small head on a long neck a short tail and four paddle-shaped limbs
plesiosaurus noun extinct marine reptile with a small head on a long neck a short tail and four paddle-shaped limbs; of the Jurassic and Cretaceous
Prehistoric carnivorous marine reptile of the Jurassic and Cretaceous periods, which reached a length of 12 m/36 ft, and had a long neck and paddlelike limbs. The pliosaurs evolved from the plesiosaurs