Brachauchenius lucasi (Williston 1903, 1907) Turonian, early Late Cretaceous ~92 mya, ~10 m in length; USNM 4989) represents the last known pliosaur in North America. Derived from a sister to Trinacromerum, Brachauchenius was a sister to its contemporary, Megacephalosaurus (below) and more distantly, Kronosaurus.

Overall larger and distinct from Trinacromerum, the skull of Brachauchenius was relatively longer, wider and flatter. The orbits (eye sockets) were angled anteriorly and so appear to provide binocular vision. A notch appeared between the premaxilla and maxilla. The cervicals were relatively more gracile. The dorsal ribs were longer. The femur was much longer than the humerus.

Megacephalosaurus eulerti (Schumaker, Carpenter and Everhart 2013) renames FHSM VP321. It is larger than Brachauchenius with smaller eyes.

Hampe O 2005. Considerations on a Brachauchenius skeleton (Pliosauroidea) from the lower Paja Formation (late Barremian) of Villa de Leyva area (Colombia). Fossil Record - Mitteilungen aus dem Museum für Naturkunde in Berlin 8 (1): 37-51.

Schumacher BA, Carpenter K and Everhart MJ 2013. A new Cretaceous pliosaurid (Reptilia, Plesiosauria) from the Carlile Shale (Middle Turonian) of Russell County, Kansas. Journal of Vertebrate Paleontology 33(3):613–628.

Williston SW 1903. North American plesiosaurs. Field Columbian Museum, Pub. 73, Geological Series 2 (1):1-79.

Williston SW 1907. The skull of Brachauchenius, with special observations on the relationships of the plesiosaurs. United States National Museum Proceedings 32: 477-489.

wiki/Brachauchenius

wiki/Megacephalosaurus