Duriavenator
Duriavenator | |
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Reconstruction of the skull with holotype elements shown in white | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Clade: | Dinosauria |
Clade: | Saurischia |
Clade: | Theropoda |
Family: | †Megalosauridae |
Subfamily: | † Megalosaurinae
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Genus: | †Duriavenator Benson, 2008 |
Species: | †D. hesperis
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Binomial name | |
†Duriavenator hesperis (Waldman, 1974)
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Synonyms | |
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Duriavenator is a
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 in the Middle Jurassic.
Discovery
In 1882, the British scientist and businessman Edward Cleminshaw obtained
In 1883, Owen considered these fossils to have belonged to the species
The specimen (today catalogued as NHM R332 at the
New species and genus
The German palaeontologist
In the 1970s, the American palaeontologists
The British palaeontologist
In 2008, the British palaeontologist Roger B. J. Benson and colleagues concluded that only the
Description
Duriavenator is estimated to have been 5–7 m (16–23 ft) long and weighed 1 t (2,200 lb), and has been described as a medium-sized theropod, comparable to Megalosaurus in size (size estimates of incompletely known dinosaurs are extrapolated from better known relatives). As a
Upper jaw
The front surface of the holotype premaxilla is inclined hindward and upwards at an angle of about 50 degrees relative to the lower margin, an angle comparable to the megalosaurid
The holotype specimen only preserves two
The frontwards directed anterior process of the maxilla is about as long as it is high, which is long compared to some theropods, like non-tetanurans,
All 11 tooth sockets of the maxilla contain emerging or fully-erupted teeth; based on comparison with the similar maxilla of Dubreuillosaurus, 14–16 teeth may have been present in the complete bone, whereas comparison based on Megalosaurus would indicate fewer than 14 teeth. On the inwards side of the maxilla,
Lower jaw
The dentary of the lower jaw has tall, roughly pentagonal interdental plates on the inwards side of the tooth row, and the inwards sides of these plates have a weakly pitted texture. The plates are separated from the inner wall of the dentary by a paradental groove, which is wide at the front, but narrow hind-wards by the fourth tooth socket, where the inner wall of the dentary contacts the interdental plates. The symphyseal region at the front of the dentary (where the two halves of the lower jaw connected) appears to have been much less distinct than that of Allosaurus. There are three front and upwards curving ridges on the dentary, oriented parallel to the lower surface at the front of the dentary, similar to Magnosaurus and other megalosauroids.[4]
The Meckelian groove which runs along the inner surface of the dentary is inclined towards the back and downwards, and is wide and shallow. The lower margin of this groove is better defined than its upper margin, particularly in front of the Meckelian fossa, where it forms a sharp, convex lip. There are two Meckelian foramina in succession close to the front end of the groove, both with roughly oval outlines. The outer surface of the dentary is smooth, with about 14 neurovascular foramina randomly arranged at the front. Further back, there is a longitudinal row of slit-like foramina in a groove just above mid-height, positioned towards the bottom so they are not visible in side view.[4]
The right dentary only preserves parts of the first 13 tooth sockets; comparison with Allosaurus indicates there would only have been one or two more tooth sockets, totalling 14 or 15, which is comparable to the estimate of tooth socket number in the maxilla. Emerging teeth are present in five tooth sockets, and replacement teeth are visible between the interdental plates next to four sockets. The first three tooth sockets are roughly circular, and the third is the largest of them all. The sockets behind the third are roughly rectangular, and decrease in size hind-wards. By the third tooth socket, the dentary expands to the sides to accommodate the enlarged socket, as seen in Magnosaurus and megalosaurids other than Megalosaurus. The second tooth of the right dentary is the only well-preserved adult tooth from the front of a dentary known from any megalosauroid, except for the family
Classification
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. Benson stated in 2008 that it was important to confirm the tetanuran status of early members of the group, such as Duriavenator, by detailed description and comparisons, so they could be included in phylogenetic analyses and the evolutionary origins of the group be examined. 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.[4]
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
In 2010, after re-evaluating various fossils historically assigned to Megalosaurus, Benson performed a phylogenetic analysis, the first to focus on basal tetanurans. He confirmed that Megalosauroidea (which had also been called Spinosauroidea previously) included the two families Megalosauridae and Spinosauridae, and that Megalosauridae was a natural group. This was also the first time Duriavenator was included in such an analysis, and it was found to group within Megalosauridae in a basal position. Benson found that almost all large-bodied theropods from the Middle Jurassic were megalosauroids, with geographic differentiation among
In 2012, the American palaeontologist Matthew T. Carrano, Benson and
Megalosauroidea |
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In their 2016 description of the megalosaurid
Palaeobiology
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
Palaeoenvironment
The only known Duriavenator specimen was collected from the Upper Inferior Oolite
References
- ^ S2CID 129235955.
- OCLC 13370987.
- ^ "Report of a meeting of the Dorset Natural History and Antiquarian Field Club". Dorset County Chronicle. June 15, 1882. p. 7.
- ^ .
- ^ .
- ^ S2CID 85354215.
- ^ a b Waldman, Michael (1974). "Megalosaurids from the Bajocian (Middle Jurassic) of Dorset". Palaeontology. 17 (2): 325–339.
- ISSN 2545-6377.
- S2CID 86378219.
- ^ Mortimer, Mickey. "Megalosauroidea". theropoddatabase.com. Retrieved 9 November 2021.
- ^ Ford, Tracy L. "Duriavenator". www.paleofile.com. Retrieved 15 November 2021.
- ISBN 978-0-517-46890-6.
- ISBN 978-0-671-61946-6.
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- ^ Holtz Jr., Thomas R. (2000). "A new phylogeny of the carnivorous dinosaurs". GAIA. 15: 12, 38.
- ISBN 978-0-520-24209-8.
- S2CID 19004679.
- .
- ^ Black, Riley (November 6, 2012). "Finding Duriavenator". Smithsonian Magazine. Smithsonian Institution. Retrieved 9 November 2021.
- S2CID 140647073.
- ^ a b Holtz Jr., Thomas R. (2012). "Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages, Appendix" (PDF). Retrieved January 12, 2012.
- ^ ISBN 978-0-691-16766-4.
- ISBN 978-0957453050.
- S2CID 53511727.
- S2CID 54901064.
- ^ Benson, Roger B. J.; Barrett, Paul M. (2009). "Dinosaurs of Dorset: Part I, the carnivorous dinosaurs (Saurischia, Theropoda)". Proceedings of the Dorset Natural History and Archaeological Society. 130: 137–138. Archived from the original on 2021-11-09. Retrieved 2021-11-12.
- ISBN 978-0-375-82419-7.
- ISBN 9780511536045.
- .
- ISBN 978-0-520-24209-8.