Duriavenator
Duriavenator is a genus of theropod dinosaur that lived in what is now England during the Middle Jurassic, about 168 million years ago. In 1882, upper and lower jaw bones of a dinosaur were collected near Sherborne in Dorset, and Richard Owen considered the fossils to belong to the species Megalosaurus bucklandii, the first named non-bird dinosaur. By 1964, the specimen was recognised as belonging to a different species, and in 1974 it was described as a new species of Megalosaurus, M. hesperis; the specific name means 'the West' or 'western'. Later researchers questioned whether the species belonged to Megalosaurus, in which many fragmentary theropods from around the world had historically been placed. After examining the taxonomic issues surrounding Megalosaurus, Roger B. J. Benson moved M. hesperis to its own genus in 2008, Duriavenator; this name means "Dorset hunter".
Estimated to have been 5–7 m (16–23 ft) long and weighed 1 t (2,200 lb), Duriavenator has been described as a medium-sized theropod. Duriavenator is distinct in features of the maxilla, the main bone of the upper jaw; it has a deep groove on the upper surface of the jugal process with numerous pneumatic (air-filled) foramina (openings), and small foramina on the lower part of the surface that connected with the premaxilla, the front bone of the upper jaw. It had about four teeth in the premaxilla, about 14–16 in the maxilla behind, and about 14–15 in the dentary of the lower jaw. While its classification was long uncertain, phylogenetic analyses in 2010 and onwards have shown it to be among the oldest tetanuran theropods (a diverse group that includes modern birds), and to belong in the family Megalosauridae. The long teeth at the front of the lower jaw may have been used for plucking and grasping during feeding. Duriavenator is known from the Upper Inferior Oolite Formation which is Bajocian in age, a stage in the Middle Jurassic.
In 1882, the British scientist and businessman Edward Cleminshaw obtained skull bones and teeth of a dinosaur from the freestone of the Inferior Oolite in Greenhill near Sherborne in Dorset, England. Blocks of the quarry-stone were being prepared for a building when Cleminshaw detected fossils embedded in them on cracked surfaces of the stones, and all such stones were withdrawn from the building yard.[1][2] Cleminshaw presented the fossils at an 1882 meeting of the Dorset Natural History and Antiquarian Field Club, where he expressed hope that more remains would be found when the quarry had been worked, and that he would send them to the British naturalist Richard Owen for examination at the British Museum.[1][3]
In 1883, Owen considered these fossils to have belonged to the species Megalosaurus bucklandii (using the now obsolete spelling M. bucklandi), which had been scientifically described and named in 1824, making it the first named non-bird dinosaur. Owen found the jaws of the then known Megalosaurus specimens to only differ in size, and due to the similarity of the teeth, thought there was no reason to divide them into different species. The skull of Megalosaurus was only known from fragments, so these new fossils aided Owen in producing a more complete reconstruction of it, incorporating the various specimens, guided by the skull of a monitor lizard. Owen believed the large opening behind the maxilla (the main bone of the upper jaw) to be the eye socket, while this is now known to be the antorbital fenestra, a large opening in front of the eye socket of many dinosaurs and their relatives.[1][4][5]
