Named By: Gasparini - 1997.
Classification: Chordata, Reptilia, Sauropterygia, Plesiosauria, Rhomaleos
Species: M. coccai (type).
Known locations: Argentina, Los Molles Formation.
Time period: Bajocian of the Jurassic.
Fossil representation: Complete skull and mandible (lower jaw) and some cervical (neck) vertebrae.
Maresaurus is one of the rhomaleosaurid pliosaurs, a group that seem to be between the long necked plesiosaurs and short necked pliosaurs in form. Additionally the fact that Maresaurus comes from South America combined with the presence of Yuzhoupliosaurus in China, produces a picture of the rhomaleosaurid pliosaurs having a global distribution. Other and older members of the group such as Macroplata and Rhomaleosaurus are so far only known from Europe where the largest number and most complete remains are known.