Megalosaurus, (meaning “Great Lizard”), is a genus of large meat-eating theropod dinosaurs of the Middle Jurassic period (Bathonian stage, 166 million years ago) of Southern England. Although fossils from other areas have been assigned to the genus, the only certain remains of Megalosaurus come from Oxfordshire and date to the late Middle Jurassic.
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 may have been the first dinosaur, apart from modern birds, to be described in the scientific literature. The earliest possible fossil of the genus, from the Taynton Limestone Formation, was the lower part of a femur, discovered in the 17th century. It was originally described by Robert Plot as a thighbone of a Roman war elephant, and then as a biblical giant. Part of a bone was recovered from the Taynton Limestone Formation of Stonesfield limestone quarry, Oxfordshire in 1676. Sir Thomas Pennyson gave the fragment to Robert Plot, Professor of Chemistry at the University of Oxford and first curator of the Ashmolean Museum, who published a description and illustration in his Natural History of Oxfordshire in 1676. It was the first illustration of a dinosaur bone published. Plot correctly identified the bone as the lower extremity of the thighbone or femur of a large animal and he recognized that it was too large to belong to any species known to be living in England. He therefore at first concluded it to be the thighbone of a Roman war elephant and later that of a giant human, such as those mentioned in the Bible. The bone has since been lost, but the illustration is detailed enough that some have since identified it as that of Megalosaurus.
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.
When this dinosaur was alive it was quite a formidable beast. It was approximately 30 feet long, 10 feet tall at the hips and weighed approximately a ton. It was an aggressive hunter that relied on its natural speed and powerful jaws to take down its prey. Scientists believe this dinosaur combed coastal regions to hunt plesiosaurs or to scavenge fish that have washed upon the shore. This scenario was put forward because many of this dinosaur’s fossil remains have been found with marine deposits.
Likely, this dinosaur not only hunted Plesiosaurs or washed up fish, but probably used several hunting strategies. It was one of the smartest of the dinosaurs of the time and probably adapted its hunting style according to the prey that was available.