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".

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.

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.

[8] In 1964, the British palaeontologist Alick D. Walker stated that while the specimen was commonly accepted as belonging to Megalosaurus bucklandii, it had more teeth in the maxilla, was older, and at least distinct at the species level.

[9] The British palaeontologist Michael Waldman further prepared the specimen in 1964–1965 and made it the holotype (on which the scientific name is based)[1] of a new species of Megalosaurus, M. hesperis in 1974.

The distinction was based on its higher tooth count in both the upper and lower jaws, but he cautioned no further comparisons could be made due to lack of material.

[1] In the 1970s, the American palaeontologists Samuel P. Welles and Jaime Emilio Powell prepared a study on European theropods, planning to move the species to the new genus "Walkersaurus".

[13] The Australian palaeontologist Ralph E. Molnar and colleagues stated in 1990 that M. hesperis could plausibly be retained in Megalosaurus, as it resembled M. bucklandii in several characters.

[15] Holtz and colleagues cautioned in 2004 that while plausible, there was no diagnostic, derived feature that could support the assignment of the species to Megalosaurus, and listed it as an unnamed tetanuran (a diverse group of theropod dinosaurs that includes modern birds).

[16] In 2007, the British palaeontologists Darren Naish and David M. Martill stated that while a valid species, ‘M.’ hesperis was probably not assignable to Megalosaurus, and did not preserve enough information to reliably classify it within Tetanurae.

Though the outer side surface of the premaxilla is poorly preserved, randomly distributed nutrient foramina (openings for blood-vessels) are visible towards its front.

One of these foramina probably opened into a canal for the nerve or blood vessel that also continued into the foramen on the surface of the maxilla that connected with the premaxilla, a feature also seen in Megalosaurus.

Waldman suggested there were five tooth sockets in the premaxilla, and if this is true, Duriavenator would have been unique among megalosauroids, which have either lower or higher numbers of premaxillary teeth.

[5] Until it was re-described and moved to its own genus Duriavenator in 2008, the higher level classification of the species was unclear, due to the fragmentary nature of its fossils and lack of detailed study.

Researchers were unable to classify it more specifically within Tetanurae, a diverse group of theropods which dominated the predator niche from the Middle Jurassic and until the end of the Cretaceous, and also includes modern birds.

Being Bajocian in age (a stage in the Middle Jurassic), Duriavenator and Magnosaurus are some of the oldest known tetanurans, with supposed older members of the group having been misidentified.

[5] In addition to being distinct from Megalosaurus (including in features like an enlarged, roughly circular third dentary tooth socket and front dentary teeth that are inclined forwards), Benson identified tetanuran features in Duriavenator (including a prominent front process of the maxilla and band-like enamel wrinkles on the teeth), and noted he would subsequently examine whether the family Megalosauridae, which it and many other British theropods had been previously grouped in, was a monophyletic (natural) group.

[6] In 2012, the American palaeontologist Matthew T. Carrano, Benson and Scott D. Sampson examined the phylogeny of Tetanura, and found Duriavenator to group in the subfamily Megalosaurinae along with Megalosaurus and Torvosaurus.

The following cladogram shows the position of Duriavenator within Megalosauroidea according to Carrano and colleagues, 2012:[7] Piatnitzkysauridae Streptospondylus Eustreptospondylus Duriavenator Megalosaurus Torvosaurus Leshansaurus Afrovenator Magnosaurus Piveteausaurus Dubreuillosaurus Poekilopleuron Spinosauridae In their 2016 description of the megalosaurid Wiehenvenator, the German palaeontologist Oliver W. M. Rauhut and colleagues included a cladogram which they found to be in perfect accordance with the stratigraphic appearance of the taxa included.

It showed Duriavenator as the most basal member of Megalosaurinae, which was in accordance with its older, Bajocian age, followed by Megalosaurus from the Bathonian, Wiehenvenator from the Callovian, and finally Torvosaurus from the Kimmeridgian-Tithonian.

[25] Benson and Barrett pointed out in 2009 that the teeth at the front of the dentary in Duriavenator were longer than those at the back, were circular in cross-section, and were slightly inclined forwards, and that such heterodonty (difference in tooth morphology) seen in megalosauroids and some other theropods may be associated with plucking or precise grasping during feeding.

[26] Holtz stated in 2012 that lighter megalosaurids, with their long, shallow snouts and relatively weak bites, would have relied on their stout, well-muscled arms to catch and kill their prey.