Source : Webster's Revised Unabridged Dictionary (1913)

Sauropterygia \Sau*rop`te*ryg"i*a\, n. pl. [NL., fr. Gr. ? a
   lizard + ?, ?, a wing.] (Paleon.)
   Same as {Plesiosauria}.

Plesiosauria \Ple`si*o*sau"ri*a\, n. pl. [NL. See
   {Plesiosaurus}.] (Paleon.)
   An extinct order of Mesozoic marine reptiles including the
   genera Plesiosaurus, and allied forms; -- called also
   {Sauropterygia}.

Source : WordNet®

Sauropterygia
     n : extinct marine reptiles: plesiosaurs; nothosaurs [syn: {order
         Sauropterygia}]