Genus: Megalneusaurus KNIGHT, 1898
Etymology: Greek, megal- (megas), “great”, Greek, neus- (neo), “swim”, Greek, sauros, “lizard”: Great swimming reptile.

Species: rex KNIGHT, 1898
Etymology:

Holotype: UW 4602

Locality: Natrona County, Wyoming.

Horizon:

Biostratigraphy:

Age: Late Jurassic.

Material: Cervical, dorsal and caudal vertebrae, humerus, ulna, radius, phalanges, ribs and greater portion of the pectoral girdle.
Note: Paleopathology, 2 humeri shows avascular necrosis (ROTHSCHILDS & STORRS, 2003)