Though represented by relatively small forms throughout the Turonian and Santonian, such as Clidastes, the lineage diversified during the Campanian and had by the Maastrichtian grown into the most diverse and species-rich mosasaur subfamily.

[5] The etymology of the group derives from the genus Mosasaurus (Latin Mosa = "Meuse river" + Greek sauros = "lizard").

Dorsal edge of surangular thin lamina of bone rising anteriorly to posterior surface of coronoid...At least 31, usually 42–45 presacral vertebrae present.

Length of presacral series exceeds that of postsacral, neural spines of posterior caudal vertebrae elongated to form distinct fin.

[6] "Clidastini" or the adjective "clidastine" is also used sometimes, but generally refers to an adaptive grade close to and containing the genus Clidastes, rather than an actual clade.