In 2005, paleontologist Johan Lindgren suspected that "Hainosaurus pembinensis" was actually a species of "Tylosaurus" but stated that a better description of MT 2 was needed to be certain. In 2010, paleontologists Timon Bullard and Michael Caldwell redescribed such specimen. They argued that the pygal vertebrae reported by Nicholls (1988) actually belonged to another individual mosasaur, reducing the vertebral count in MT 2 to one that was indistinguishable with "Tylosaurus". They also noted that the length of the external nares was within the known range of "Tylosaurus" and additionally argued that the femur being longer than the humerus was an insufficient characteristic to diagnose the species at the generic level. Based on these and other characteristics, the study found that the species cannot be referred to "Hainosaurus" and renamed it to "Tylosaurus pembinensis". With this rediagnosis, the study also noted that the only confirmed characteristic that distinguished "Hainosaurus" from "Tylosaurus" at the time was a higher count of pygal vertebrae. It was doubted as to if this would be sufficient enough for "Hainosaurus" to be a distinct genus but acknowledged that further research may provide additional characteristics. This further research was done in 2016 by Paulina Jimenez-Huidobro and Caldwell, which reexamined "H. bernardi". They found that the unique characteristics of the type species are indeed insufficient to warrant a distinction between "Hainosaurus" and "Tylosaurus" and declared the former as a junior synonym of the latter, thus renaming "H. bernardi" to "Tylosaurus bernardi". However, this synonymization is controversial and some scientists continue to argue that "Hainosaurus" is a distinct genus, justified by differences in tooth morphology unexplored by Jimenez-Huidobro & Caldwell (2016) such as the presence of an advanced cutting-based dentition in "T. bernardi" as opposed to a more general smashing-based dentition seen in other "Tylosaurus" species.