The only known remains of Regnosaurus are the holotype BMNH 2422, the right fragment of the lower jaw. The fragment has a length of 15.5 cm and includes 15 dental alveoli. You may also notice several uncut teeth. Some other fossils, such as petrified pelvic bones found on the Isle of Wight , were also attributed to this genus, but due to the lack of a complete skeleton, their unambiguous identification is difficult. The same is true for the skin spikes found by paleoanthologist William Blous in 2001 [1] .
The dinosaur allegedly possessed a body structure characteristic of all stegosaurs . Most likely, it was relatively small in size, about 4 meters in length.
The fossilized remains, which are fragments of the lower jaw, were discovered near the village of Cuckfield ( en: Cuckfield ) in West Sussex , England , and were exhibited at the London Museum of Natural History [2] . In 1839, Gideon Mantell noted that he paid attention to the remains when visiting the museum. Mantell soon concluded that these fragments of the jaw belong to the iguanodon , moreover, to the cub (whose jaw had not yet been described). On February 8, 1841, he presented fragments as the jaw of the iguanodon to the Royal Society of London . Richard Owen hastened to refute this statement, on the basis of a lack of clear evidence. Later, in 1848, when the true jaws of the iguanodon were found, Mantell changed his mind and attributed fragments of the holotype to a separate species and genus, which he gave the name Regnosaurus Northamptoni [3] . The generic name Regnosaurus comes from the name of the tribe of Regns , who once lived on the territory of Sussex. The specific name Northamptoni was given in honor of Spencer Joshua Compton , Earl of Northampton , who at that time was just about to resign as president of the Royal Society [4] . In accordance with modern binary nomenclature rules, the correct species name is Regnosaurus northampthoni .
Originally considered an iguanodontid , Regnosaurus was later assigned to armored dinosaurs. In 1888, Richard Lidecker attributed the lizards to the Scelidosauridae group, Friedrich von Hunet in 1909 classified him as a member of the now abolished Omosauridae group, and in 1911 Karl Alfred von Zittel assigned the lizards to Stegosauridae. However, all these groups at that time had different borders, and also included armored dinosaurs. As for Regnosaurus, there were completely original ideas - for example, John Ostrom suggested that he was generally a sauropod .
The first to suggest that Regnosaurus is a stegosaurus in the modern sense of the word was George Olszewski in 1993 [5] . This assumption was confirmed by Paul Barett and Paul Apcherch in 1995, who concluded that the lizard is very close to the gileosaurus due to the similarity of the jaws [6] . Due to the fact that the remains of Regnosaurus are so incomplete and rare (in fact, only fragments of the jaw clearly belong to the species), many scientists believe that Regnosaurus northamthoni is a nomen dubium within the suborder of thyroids [7] .
