Sauropterygian yakatanga kuoneka makore angangoita mamirioni makumi maviri nemashanu apfuura (Ma), pakutanga kweTriassic nguva: yekutanga sauropterygian ine chaiyo stratigraphic datum iri mukati meSpathian chikamu cheOlenekian nguva muSouth China. Mienzaniso yekutanga yaive diki (anenge 60 cm), semi-aquatic lizard-senge mhuka dzine makumbo marefu (pachypleurosaurs), asi ivo vakakurumidza kukura kuva mamita akati wandei kureba uye vakapararira mumvura isina kudzika (nothosaurs). Chiitiko cheTriassic-Jurassic chekutsakatika chakavabvisa vese kunze kweiyo plesiosaurs. Munguva yeKutanga Jurassic, izvi zvakakurumidza kusiyaniswa kuva ese marefu-muswe-muswe plesiosaurs, uye mapfupi-muswe-muswe plesiosaurs. Pakutanga, zvaifungidzirwa kuti plesiosaurs uye plesiosaurs vaive vaviri vakasarudzika superfamily nemitezo miviri yakasarudzika. Panguva yekushanduka kwekutanga, zvinoita sekunge vaviri ava vatevedzana nemhando mbiri dzakasiyana dzemhando dzakasiyana dzem
plesiosaurs chaiyo ine mitsipa mirefu ine misoro miduku, uye pliosaurs ine mitsipa mipfupi ine misoro mikuru