Scientists previously interpreted "Tylosaurus" as an anguilliform swimmer that moved by undulating its entire body like a snake due to its close relationship with the animal. However, it is now understood that "Tylosaurus" actually used carangiform locomotion, meaning that the upper body was less flexible and movement was largely concentrated at the tail like in mackerels. A BS thesis by Jesse Carpenter published in 2017 examined the vertebral mobility of "T. proriger" spinal columns and found that the dorsal vertebrae were relatively rigid but the cervical, pygal, and caudal vertebrae were more liberal in movement, indicating flexibility in the neck, hip, and tail regions. This contrasted with more derived mosasaurs like "Plotosaurus", whose vertebral column was stiff up to the hip. Interestingly, an examination of a juvenile "T. proriger" found that its cervical and dorsal vertebrae were much stiffer than those in adult specimens. This may have been an evolutionary adaptation among young individuals; a more rigid tail-based locomotion is associated with faster speed, and this would allow vulnerable juveniles to better escape predators or catch prey. Older individuals would see their spine grow in flexibility as predator evasion becomes less important for survival.