Hainosaurus
Hainosaurus ("Haino" from the river Haine, where it was first discovered, and "saurus", from Greek sauros, meaning lizard) is an extinct genus of marine reptiles belonging to the mosasaur family. It is one of the largest mosasaurs, though its size has been revised more than once. At first it was estimated to be , and the largest mosasaurid. During the 1990s, its size was revised to long; more recently, Johan Lindgren estimated that it reached lengths of up to . It was one of the top marine predators of the Late Cretaceous. Like other giant mosasaurs, this giant predator preyed on  turtles, plesiosaurs, pterosaurs, cephalopods, sharks, fish, and smaller mosasaurs. History. In 1885, Louis Dollo described the genus "Hainosaurus" from a near-complete but poorly preserved skeleton excavated from a phosphate quarry in the Ciply Basin near the town of Mesvin, Belgium. The fossil was initially discovered as eight vertebrae by a worker in the January of the same year, who sold them to the Royal Belgian Institute of Natural Sciences. Based on information about the circumstances and locality of the discovery given the museum, it was recognized that the rest of the skeleton may have remained intact. In February, excavations  were made under the authorization of an industrialist named Leopold Bernard, who managed the quarry the fossil resided in. The rest of the skeleton was recovered after a month of excavating between of phosphate, although a section of the tail was found to have been destroyed by erosion from an overlying deposit. The skeleton went to the museum, which was subsequently studied by Dollo, who recognized that it belonged to a new type of mosasaur. By instruction of the museum, he named it "Hainosaurus bernardi". The prefix "Haino"- in the generic name refers to the Haine, a river located nearby  the Ciply Basin, and thus combined with means "lizard from the Haine"; Dollo wrote that this was erected specifically to complement the etymology of "Mosasaurus", which was similarly named in reference to a river near its type locality. The specific epithet "bernardi" was in recognition of Bernard, who made the excavation of the skeleton possible. The skeleton is now on display at the Royal Belgian Institute under the catalog number IRSNB R23. A second species historically pertained to "Hainosaurus" was described by in 1988 by Elizabeth Nicholls based on a partial skeleton consisting of a partial skull, lower jaw, a  near-complete vertebral column, and some limb bones recovered from the Pembina Member of the Pierre Shale in Manitoba, Canada. This skeleton resides in the Miami Museum in Miami, Manitoba cataloged as MT 2. Although "Hainosaurus" was previously only known in Europe, Nicholls (1988) argued that the new species differed from the more locally known "Tylosaurus" based on a higher count of pygal vertebrae, longer external nares, and femur longer than the humerus. The species was named "Hainosaurus pembinensis", the specific epithet referring to the Pembina Member the skeleton was found in. 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, some scientists argue that "Hainosaurus" should remain 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. Classification. "Hainosaurus" is a member of the subfamily Tylosaurinae, and it is related to  the wholly North American "Tylosaurus". However, it has more vertebrae from the neck to the part of the tail with chevrons (53) than "Tylosaurus" (35). Both genera are large marine superpredators. "Hainosaurus"' tail has less chevron-bearing vertebrae, making it shorter than that of "Tylosaurus". The type species of "Hainosaurus" is "H. bernardi", named after the Belgian Léopold Bernard, owner of the phosphate chalk exploitation where the fossil was unearthed. In a paper published in 2016, "Hainosaurus" was considered a species of "Tylosaurus", "T. bernardi", which was found to be the sister taxon to the type species of "Tylosaurus", "T.  proriger".