The type species is Megalosaurus bucklandii, named in 1827. In 1842, Megalosaurus was one of three genera on which Richard Owen based his Dinosauria. On Owen’s directions a model was made as one of the Crystal Palace Dinosaurs, which greatly increased the public interest for prehistoric reptiles. Subsequently, over fifty other species would be classified under the genus, originally because dinosaurs were not well known, but even during the 20th century after many dinosaurs had been discovered. Today it is understood these additional species were not directly related to M. bucklandii, which is the only true Megalosaurus species. Because a complete skeleton of it has never been found, much is still unclear about its build.
Megalosaurus’s evolutionary relationships are still something of a mystery to paleontologists. The few analyses that have been done place Megalosaurus outside the groups that include the allosaurids and the coelurosaurs and closer to an assemblage that includes the spinosaurids (including Spinosaurus and Baryonyx). However, even this possible close relationship with spinosaurids has not yet been definitively established.