plesiosaur plesiomorphous • Plesiosauri · · · Info · Definitions · Synonyms · Characters · · plesiosaur · · Text Latin · · Script 10 · · Length 5 · · Syllables Definitions · · · (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. Synonyms: plesiosaurus. · · Noun Definition 1 Synonyms · · · plesiosaurus · · Synonym 1 Characters · · a latin small letter a U+0061 e latin small letter e U+0065 i latin small letter i U+0069 l latin small letter l U+006C o latin small letter o U+006F p latin small letter p U+0070 r latin small letter r U+0072 s latin small letter s U+0073 u latin small letter u U+0075