They are highly derived mosasaurs, containing genera like Plotosaurus, having unique adaptations to fast swimming speeds, or Mosasaurus, which is among the largest known marine reptiles.

The tribe was erected by Russell in 1967, stating that it is unified by having twelve or less pygal vertebrae and that the radius and ulna are widely separated by a bridge of carpalia on the distal border of the antebrachial foramen.

[1] But In a 1997 study, paleontologist Gorden Bell recovered Plotosaurus, which was formerly classified within another tribe called the Plotosaurini, as a sister genus to Mosasaurus.

For example, in a 2012 study, Aaron LeBlanc, Caldwell, and Bardet argued that, while it is not necessarily invalid, abandoning Mosasaurini would not follow the general principle of the type genus carrying over to all ranks in a classification hierarchy, and that the original diagnostics of the Plotosaurini is outdated.

[4] The taxa Mosasaurini has historically been more inclusive, on occasion including genera such as Plesiotylosaurus,[5] Liodon and Clidastes,[1] all of which are now seen as more basal mosasaurines.