Dracovenator

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Dracovenator
Temporal range: Early Jurassic, 201–199 Ma
DracovenatorROM1.JPG
Partial skull of Dracovenator regenti
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Clade: Dinosauria
Order: Saurischia
Suborder: Theropoda
Family: Dilophosauridae
Genus: Dracovenator
Yates, 2005
Species: D. regenti
Binomial name
Dracovenator regenti
Yates, 2005

Dracovenator (/ˌdræ.k.vɛˈn.tər/) is an extinct genus of dilophosaurid theropod dinosaur that lived approximately 201 to 199 million years ago during the early part of the Jurassic Period in what is now South Africa. Dracovenator was a medium-sized, moderately-built, ground-dwelling, bipedal carnivore, that could grow up to an estimated 7 m (23.0 ft) long. Its type specimen was based on only a partial skull that was recovered.

Description[edit]

Hypothetical restoration

Dracovenator is estimated to have measured between 5.5 and 6.5 meters (18 and 21 ft) in length.[1] Others estimates suggest that Dracovenator was at most 7 m (23 ft) long and weighed 400 kilograms (882 pounds).[2] The holotype specimen, BP/1/5243, consists of both premaxillae, a fragment of the maxilla, two dentary fragments, a partial surangular bone, a partial angular bone, a partial prearticular bone, an articular bone, and several teeth. Dracovenator has a kink in its upper jaws, between the maxilla and the premaxilla. The back end of the lower jaw features an array of lumps and bumps, a condition seen in Dilophosaurus, but to a much smaller extent. Munyikwa and Raath (1999) reassigned paratype BP/1/5278, which was originally assigned to Syntarsus rhodesiensis, to Dracovenator, a juvenile specimen which consists of bones from the front of the skull, teeth, and jaw bones.[3]

Size compared to a human

A diagnosis is a statement of the anatomical features of an organism (or group) that collectively distinguish it from all other organisms. Some, but not all, of the features in a diagnosis are also autapomorphies. An autapomorphy is a distinctive anatomical feature that is unique to a given organism. According to Yates (2005) Dracovenator can be distinguished based on the following characteristics: the presence of a large bilobed fossa surrounding a large lateral premaxillary foramen that is connected to the alveolar margin by a deep narrow channel; a deep, oblique notch on the lateral surface of the articular bone, separating the retroarticular process from the posterior margin of the glenoid, a particularly well-developed dorsal, tab-like processes on the articular bone-the first on the medial side, just posterior to the opening of the chorda tympanic foramen and the second on the lateral side on the anterolateral margin of the fossa for the m. depressor mandibulae.[4]

Discovery[edit]

Drawing of the known skull bones

The type material BP/1/5243 for Dracovenator was discovered at the "Upper Drumbo Farm" locality in the Upper Elliot Formation which is part of the Stormberg Group, in Eastern Cape Province, South Africa. It was collected by James Kitching and Regent "Lucas" Huma in sandstone that was deposited during the Hettangian stage of the Jurassic period, approximately 201 to 199 million years ago. The paratype material BP/1/5278 (originally assigned to Syntarsus rhodesiensis) was discovered in 1981, also at the Upper Elliot Formation in pinkish-maroon silty mudstone that was deposited in Hettangian sediments.[3] Both the holotype and paratype specimens are housed in the collection of the Bernard Price Institute for Palaeontological Research which is part of the School of Geosciences of the University of the Witwatersrand, in Johannesburg, South Africa.

The genus name is a contraction of the Latin words draco meaning "dragon", and venator meaning "hunter"; thus, "dragon hunter". "Draco" refers to its discovery in the foothills of Drakensberg, which is "Dragon’s Mountain" in the Dutch language. The specific name, regenti, was named in the honor of the late Regent ‘Lucas’ Huma, who was Professor Kitching’s field assistant. Dracovenator was described and named by Adam M. Yates in 2006 and the type species is Dracovenator regenti.

Classification[edit]

Juvenile Dracovenator regenti snout on display at the Royal Ontario Museum, Ontario

Yates (2005) assigned Dracovenator to the clade Neotheropoda.[4] The first cladistic analysis found that this genus formed a clade with the basal theropods Dilophosaurus and Zupaysaurus. The skull of the type specimen, exhibits a mosaic of both ancestral and derived theropod characteristics. The following cladogram, based on the phylogenetic analysis conducted by Smith, Makovicky, Pol, Hammer, and Currie in 2007, outlines the relationships of Dracovenator and its close relatives:[5]


Neotheropoda

Coelophysoidea


unnamed

Neoceratosauria



Tetanurae




Zupaysaurus


unnamed
Dilophosauridae

Sinosaurus (=Dilophosaurus sinensis)


unnamed

Dracovenator


unnamed

Dilophosaurus



Cryolophosaurus










Paleoecology[edit]

holotype BP/1/5243

The Upper Elliot Formation is thought to have been an ancient floodplain. Fossils of the prosauropod dinosaur Massospondylus and Plateosaurus have been recovered from the Upper Elliot Formation, which boasts the world's most diverse fauna of early Jurassic ornithischian dinosaurs, including Abrictosaurus, Fabrosaurus, Heterodontosaurus, and Lesothosaurus, among others. The Forest Sandstone Formation was the paleoenvironment of protosuchid crocodiles, sphenodonts, the dinosaur Massospondylus and indeterminate remains of a prosauropod. Dracovenator is thought to have preyed on the prosauropod dinosaurs in its paleoenvironment.

References[edit]

  1. ^ Smith, N.D., Makovicky, P.J., Pol, D., Hammer, W.R., and Currie, P.J. (2007). "The Dinosaurs of the Early Jurassic Hanson Formation of the Central Transantarctic Mountains: Phylogenetic Review and Synthesis". U.S. Geological Survey and The National Academies doi:10.3133/of2007-1047.srp003
  2. ^ "Dracovenator". Dinochecker.com. Retrieved 19 May 2013. 
  3. ^ a b Munyikwa and Raath, 1999. Further material of the ceratosaurian dinosaur Syntarsus from the Elliot Formation (Early Jurassic) of South Africa. Palaeontologia Africana. 35:55-59.
  4. ^ a b A. M. Yates. 2005. A new theropod dinosaur from the Early Jurassic of South Africa and its implications for the early evolution of theropods. Palaeontologia Africana 41:105-122
  5. ^ Smith, N.D., Makovicky, P.J., Pol, D., Hammer, W.R., and Currie, P.J. (2007). "The dinosaurs of the Early Jurassic Hanson Formation of the Central Transantarctic Mountains: Phylogenetic review and synthesis." In Cooper, A.K. and Raymond, C.R. et al. (eds.), Antarctica: A Keystone in a Changing World––Online Proceedings of the 10th ISAES, USGS Open-File Report 2007-1047, Short Research Paper 003, 5 p.

External links[edit]