Brachauchenius lucasi (Williston 1903, 1907) Turonian, early Late Cretaceous ~92 mya, ~10 m in length represents the last known pliosaur in North America. Derived from a sister to Trinacromerum, Brachauchenius was a sister to its contemporary, 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.
The family tree of the Enaliosauria is here. The complete reptile family tree is here.