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Temporal range: Cenomanian–Santonian[1]
Orkoraptor drawing.jpg
Artist's restoration
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Order: Saurischia
Suborder: Theropoda
Clade: Megaraptora
Genus: Orkoraptor
Novas, Ezcurra & Lecuona, 2008
Species: O. burkei
Binomial name
Orkoraptor burkei
Novas, Ezcurra & Lecuona, 2008

Orkoraptor is a genus of large theropod dinosaur from the late Cretaceous Period of Argentina. It is known from incomplete fossil remains including parts of the skull, teeth, tail vertebrae, and a partial tibia. The specialized teeth resemble those of some maniraptoriform theropods, namely the deinonychosaurs and compsognathids. This and other anatomical features led the authors who described it (Novas, Ezcurra, and Lecuona) to suggest that it was a maniraptoran Coelurosaur. However, subsequent studies found it to be a megaraptoran.[2][3] Found in the Pari Aike Formation of Southern Patagonia, it is one of the southernmost carnivorous dinosaurs known from South America.[4]


The name Orkoraptor means "Toothed River thief", and was derived from the Aoniken "Orr-Korr", the local name for the La Leona River, located near the original fossil site. The species name honors Coleman Burke, an amateur paleontologist who supported the expedition that collected the original fossils.[4]


Orkoraptor was a medium-sized theropod. In 2010, Gregory S. Paul estimated its length as 6 m (20 ft) and mass as 500 kilograms.[5]:99


Orkoraptor was originally classified as Maniraptora incertae sedis. While the majority of phylogenetic trees recovered in its describers' analysis recovered it as a compsognathid, the describers considered this unlikely based on its much larger size and presence in much younger strata.[4] Orkoraptor was subsequently recovered in Megaraptora, a clade including several other enigmatic medium to large theropods, which has variously been considered to be a member of Allosauroidea and Tyrannosauroidea.[2][3][6] The phylogenetic trees in the publication of Gualicho shinyae have found megaraptorans to be either allosauroids or basal coelurosaurs.[7]


All known specimens of Orkoraptor were collected from the Pari Aike Formation, which is now considered by different authors to be either the middle section of the Mata Amarilla Formation,[1] or merely an alternative name for the Cerro Fortaleza Formation.[8][9] It was originally identified as coming from the Maastrichtian, and thus the youngest known megaraptoran, but more recently is considered to be from the Cenomanian to Santonian.[1][6] The middle section of the Mata Amarilla Formation, whence Orkoraptor was collected, contains a tuff layer that has been dated to 96.2 ± 0.7 Ma, during the Cenomanian.[1]


  1. ^ a b c d Varela, A. N.; Poiré, D. G.; Martin, T.; Gerdes, A.; Goin, F. J.; Gelfo, J. N.; Hoffmann, S. (2012). "U-Pb zircon constraints on the age of the Cretaceous Mata Amarilla Formation, Southern Patagonia, Argentina: Its relationship with the evolution of the Austral Basin". Andean Geology. 39 (3): 359–379. doi:10.5027/andgeoV39n3-a01. 
  2. ^ a b Benson, R.B.J.; Carrano, M.T; Brusatte, S.L. (2010). "A new clade of archaic large-bodied predatory dinosaurs (Theropoda: Allosauroidea) that survived to the latest Mesozoic". Naturwissenschaften. 97 (1): 71–78. Bibcode:2010NW.....97...71B. PMID 19826771. doi:10.1007/s00114-009-0614-x. 
  3. ^ a b Porfiri, Juan D.; Novas, Fernando E.; Calvo, Jorge O.; Agnolín, Frederico L.; Ezcurra, Martín D.; Cerda, Ignacio A. (2014). "Juvenile specimen of Megaraptor (Dinosauria, Theropoda) sheds light about tyrannosauroid radiation". Cretaceous Research. 51: 35–55. doi:10.1016/j.cretres.2014.04.007. 
  4. ^ a b c Novas, F.E.; Ezcurra, M.D.; Lecuona, A. (2008). "Orkoraptor burkei nov. gen. et sp., a large theropod from the Maastrichtian Pari Aike Formation, Southern Patagonia, Argentina". Cretaceous Research. 29 (3): 468–480. doi:10.1016/j.cretres.2008.01.001. 
  5. ^ Paul, G. S. (2010). The Princeton Field Guide to Dinosaurs. Princeton University Press. 
  6. ^ a b Novas, F. E.; Agnolín, F. L.; Ezcurra, M. D.; Porfiri, J.; Canale, J. I. (2013). "Evolution of the carnivorous dinosaurs during the Cretaceous: The evidence from Patagonia". Cretaceous Research. 45: 174–215. doi:10.1016/j.crecres.2013.04.001. 
  7. ^ http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0157793
  8. ^ Elena R. Schroeter; Victoria M. Egerton; Lucio M. Ibiricu; Kenneth J. Lacovara (2014). "Lamniform Shark Teeth from the Late Cretaceous of Southernmost South America (Santa Cruz Province, Argentina)". PLoS ONE. 9 (8): e104800. PMC 4139311Freely accessible. PMID 25141301. doi:10.1371/journal.pone.0104800. 
  9. ^ Kenneth J. Lacovara; Matthew C. Lamanna; Lucio M. Ibiricu; Jason C. Poole; Elena R. Schroeter; Paul V. Ullmann; Kristyn K. Voegele; Zachary M. Boles; Aja M. Carter; Emma K. Fowler; Victoria M. Egerton; Alison E. Moyer; Christopher L. Coughenour; Jason P. Schein; Jerald D. Harris; Rubén D. Martínez; Fernando E. Novas (2014). "A Gigantic, Exceptionally Complete Titanosaurian Sauropod Dinosaur from Southern Patagonia, Argentina (Supplementary information)". Scientific Reports. 4: 6196. PMID 25186586. doi:10.1038/srep06196.