Thalassiodracon ("sea dragon") is an extinct genus of small pliosaur that lived in the Late Triassic (Rhaetian) to the Early Jurassic (Hettangian) of Europe. The animal is known from a number of complete skeletons (Holotype: BMNH 2018) found by the fossil collector Thomas Hawkins in Somerset, England. The type and only species, Thalassiodracon hawkinsi named to honor its discoverer, was originally placed in the genus Plesiosaurus. This marine reptile measured 1.5-2 m. (5-6.5 ft) had a long neck but the skull was proportionally larger than Plesiosaurus, being 1/10th of the total body length.