E. D. Cope discovered the first specimens in 1869 from the Mooreville Chalk in Lowndes County, Alabama.[5] The remains unearthed were that of a juvenile but are one of the best preserved and most complete mosasaurs collected from the state and is regarded as the generic holotype of Clidastes.[3] In 1918, Charles H. Sternberg and his son found additional remains of Clidastes in Kansas.[6] They were surprised to see that it had humeri and femora with round heads, similar to that of mammals. Due to good preservation of the caudals, Sternberg noted that the chevrons along the vertebrae were ankylosed to the center, which is not observed in other mosasaurs. This synapamorphy was believed to aid in fitting the proximal heads snugly into the basins that hew out from the vertebrae almost locking t