Megalosaurus

Megalosaurus Temporal range: Middle Jurassic (Bathonian), 166–165 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Fossil specimens referred to M. bucklandii, Oxford University Museum of Natural History. The display shows most of the original syntype series, including the lectotype dentary, identified by Buckland in 1824
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Clade:	Dinosauria
Clade:	Saurischia
Clade:	Theropoda
Family:	†Megalosauridae
Subfamily:	†Megalosaurinae
Genus:	†Megalosaurus Buckland, 1824
Species:	†M. bucklandii
Binomial name
†Megalosaurus bucklandii Mantell, 1827
Synonyms
Megalosaurus bucklandi Meyer, 1832 Megalosaurus conybeari Ritgen, 1826 (nomen oblitum) Scrotum humanum Brookes, 1763 (nomen oblitum)

Megalosaurus (meaning "great lizard", from Greek μέγας, megas, meaning 'big', 'tall' or 'great' and σαῦρος, sauros, meaning 'lizard') is an extinct genus of large carnivorous theropod dinosaurs of the Middle Jurassic Epoch (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 earliest remains of Megalosaurus were described in the 17th century, and were initially interpreted as the remains of elephants or giants. Megalosaurus was named in 1824 by William Buckland, becoming the first genus of non-avian dinosaur to be validly named. The type species is M. bucklandii, named in 1827 by Gideon Mantell, after Buckland.^[1] 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. Over 50 other species would eventually be classified under the genus; at first, this was because so few types of dinosaur had been identified, but the practice continued even into the 20th century after many other dinosaurs had been discovered. Today it is understood that none of these additional species was 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.

The first naturalists who investigated Megalosaurus mistook it for a gigantic lizard 20 metres (66 ft) in length. In 1842, Owen concluded that it was no longer than 9 metres (30 ft). He still thought it was a quadruped, though. Modern scientists were able to obtain a more accurate picture, by comparing Megalosaurus with its direct relatives in the Megalosauridae. Megalosaurus was about 6 metres (20 ft) long, weighing about 700 kilograms (1,500 lb). It was bipedal, walking on stout hindlimbs, its horizontal torso balanced by a horizontal tail. Its forelimbs were short, though very robust. Megalosaurus had a rather large head, equipped with long curved teeth. It was generally a robust and heavily muscled animal.

At the time Megalosaurus lived, Europe formed an island archipelago around the Tethys Ocean, with Megalosaurus inhabiting an island formed by the London–Brabant Massif, where it likely served as the apex predator of its ecosystem, coexisting with other dinosaurs like the large sauropod Cetiosaurus.