Orkoraptor

Last updated

Orkoraptor
Temporal range: Late Cretaceous, 76–70  Ma
Orkoraptor drawing.jpg
Artist's restoration
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Clade: Saurischia
Clade: Theropoda
Clade: Megaraptora
Family: Megaraptoridae
Genus: Orkoraptor
Novas, Ezcurra & Lecuona, 2008
Species:
O. burkei
Binomial name
Orkoraptor burkei
Novas, Ezcurra & Lecuona, 2008

Orkoraptor is a genus of medium-sized megaraptoran 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. [1] [2] Found in the Cerro Fortaleza Formation of Southern Patagonia, it is one of the southernmost carnivorous dinosaurs known from South America. [3]

Contents

Etymology

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. [3]

Description

Orkoraptor was a medium-sized theropod, measuring 6 m (20 ft) long and weighing 500 kilograms (1,100 lb). [4] [5] The holotype, MPM-Pv 3457 was excavated in 2001 and consists of a right postorbital, a right quadratojugal, a probable right coronoid, eight isolated teeth, the intercentrum of the atlas and its right neurapophysis, two proximal caudal vertebrae, the proximal half of the right tibia, eight fragmentary ribs, and three incomplete chevrons. It was initially believed to be a coelurosaur due to the upturned anterior process of the postorbital as well as specialized teeth which are unserrated on the mesial (front) side and have an 8-shaped cross section, similar to those of dromaeosaurids and compsognathids. However, many other features contradict those of these families and other coelurosaurs, so its original describers were unable to conclusively assign it to any specific family. They did note its similarity to a then-undescribed Patagonian theropod now known as Murusraptor . [3] More recent analyses have explained that these coelurosaur-like traits are also present in some megaraptorans. For example, Orkoraptor's postorbital is almost identical to that of Aerosteon [1] and the juvenile Megaraptor described in 2014 has teeth similar to those of Orkoraptor. [2]

Classification

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. [3] 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. [1] [2] [6] The phylogenetic trees in the publication of Gualicho shinyae have found megaraptorans to be either allosauroids or basal coelurosaurs. [7]

Provenance

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, [8] or merely an alternative name for the Cerro Fortaleza Formation. [9] [10] 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. [8] [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. [8] However, the site where Orkoraptor is known from, Cerro Hornos, was recently reinterpreted as coming from the Campanian. [11]

Related Research Articles

<i>Fukuiraptor</i> Megaraptoran theropod dinosaur genus from the Early Cretaceous epoch

Fukuiraptor was a medium-sized megaraptoran theropod dinosaur of the Early Cretaceous epoch that lived in what is now Japan. Fukuiraptor is known from the Kitadani Formation and possibly also the Sebayashi Formation.

<span class="mw-page-title-main">Carcharodontosauridae</span> Extinct family of dinosaurs

Carcharodontosauridae is a group of carnivorous theropod dinosaurs. In 1931, Ernst Stromer named Carcharodontosauridae as a family, which, in modern paleontology, indicates a clade within Carnosauria. Carcharodontosaurids include some of the largest land predators ever known: Giganotosaurus, Mapusaurus, Carcharodontosaurus, and Tyrannotitan all rivaled Tyrannosaurus in size. Estimates give a maximum weight of 8–10 metric tons for the largest carcharodontosaurids, while the smallest carcharodontosaurids were estimated to have weighed at least 500 kilograms (1,100 lb).

<i>Deltadromeus</i> Theropod dinosaur genus from mid-Cretaceous Period

Deltadromeus is a genus of theropod dinosaur from Northern Africa. It had long, unusually slender hind limbs for its size, suggesting that it was a swift runner. The skull is not known. One fossil specimen of a single species has been described, found in the Kem Kem Beds, which date to the mid-Cretaceous Period, about 95 million years ago. It may be a junior synonym of the contemporary Bahariasaurus. The classification of Deltadromeus has been in flux since its original description. In 2016, a South American theropod known as Gualicho shinyae was found to possess many similarities with Deltadromeus. Depending on the phylogenetic position of Gualicho, Deltadromeus may have been a neovenatorid carnosaur, a tyrannosauroid, or a basal coelurosaur if its close relation to Gualicho is legitimate. Other studies have considered it a ceratosaurian, more specifically a member of the family Noasauridae.

<i>Megaraptor</i> Extinct genus of dinosaurs

Megaraptor is a genus of large theropod dinosaur that lived in the ages of the Late Cretaceous. Its fossils have been discovered in the Patagonian Portezuelo Formation of Argentina, South America. Initially thought to have been a giant dromaeosaur-like coelurosaur, it was classified as a neovenatorid allosauroid in previous phylogenies, but more recent phylogeny and discoveries of related megaraptoran genera has placed it as either a basal tyrannosauroid or a basal coelurosaur with some studies still considering it a neovenatorid.

<i>Talenkauen</i> Extinct genus of dinosaurs

Talenkauen is a genus of basal iguanodont dinosaur from the Campanian or Maastrichtian age of the Late Cretaceous Cerro Fortaleza Formation, formerly known as the Pari Aike Formation of Patagonian Lake Viedma, in the Austral Basin of Santa Cruz, Argentina. It is based on MPM-10001A, a partial articulated skeleton missing the rear part of the skull, the tail, and the hands. The type and only species is Talenkauen santacrucensis.

The Bajo de la Carpa Formation is a geologic formation of the Neuquén Basin that crops out in northern Patagonia, in the provinces of Río Negro and Neuquén, Argentina. It is the oldest of two formations belonging to the Río Colorado Subgroup within the Neuquén Group. Formerly, that subgroup was treated as a formation, and the Bajo de la Carpa Formation was known as the Bajo de la Carpa Member.

<i>Puertasaurus</i> Extinct genus of dinosaurs

Puertasaurus is a genus of sauropod dinosaur that lived in South America during the Late Cretaceous Period. It is known from a single specimen recovered from sedimentary rocks of the Cerro Fortaleza Formation in southwestern Patagonia, Argentina, which probably is Campanian or Maastrichtian in age. The only species is Puertasaurus reuili. Described by the paleontologist Fernando Novas and colleagues in 2005, it was named in honor of Pablo Puerta and Santiago Reuil, who discovered and prepared the specimen. It consists of four well-preserved vertebrae, including one cervical, one dorsal, and two caudal vertebrae. Puertasaurus is a member of Titanosauria, the dominant group of sauropods during the Cretaceous.

<i>Aerosteon</i> Extinct genus of dinosaurs

Aerosteon is a genus of megaraptoran dinosaur from the Late Cretaceous period of Argentina. Its remains were discovered in 1996 in the Anacleto Formation, which is from the late Campanian. The type and only known species is A. riocoloradensis. Its specific name indicates that its remains were found 1 km north of the Río Colorado, in Mendoza Province, Argentina.

<span class="mw-page-title-main">Bahariasauridae</span> Probable family of averostran theropods

Bahariasauridae is a potential family of averostran theropods that might include a handful of African and South American genera, such as Aoniraptor, Bahariasaurus, Deltadromeus, and Gualicho. The placement of these theropods is controversial, with some studies placing them as basal ceratosaurs possibly related to Noasauridae, others classifying them as megaraptorans, basal neovenatorids, or basal coelurosaurs. There is also a possibility the group might not be monophyletic, as a monograph on the vertebrate diversity in the Kem Kem Beds published in 2020 found Bahariasaurus to be nomen dubium. In the same paper Deltadromeus is classified as an noasaurid, a result also recovered by some previous studies.

<i>Australovenator</i> Extinct genus of dinosaurs

Australovenator is a genus of megaraptoran theropod dinosaur from Cenomanian -age Winton Formation of Australia. It is known from partial cranial and postcranial remains which were described in 2009 by Scott Hocknull and colleagues, although additional descriptions and analyses continue to be published. It is the most complete predatory dinosaur discovered in Australia. It has been suggested that Australovenator is a sister taxon to Fukuiraptor, although some phylogenetic analyses find it to be a more derived member of the Megaraptora, possibly being part of the main Megaraptoridae family itself.

<span class="mw-page-title-main">Neovenatoridae</span> Extinct family of dinosaurs

Neovenatoridae is a proposed clade of carcharodontosaurian dinosaurs uniting some primitive members of the group such as Neovenator with the Megaraptora, a group of theropods with controversial affinities. Other studies recover megaraptorans as basal coelurosaurs unrelated to carcharodontosaurs. Other theropods with uncertain affinities such as Gualicho, Chilantaisaurus and Deltadromeus are also sometimes included.

<span class="mw-page-title-main">Megaraptora</span> Extinct clade of dinosaurs

Megaraptora is a clade of carnivorous tetanuran theropod dinosaurs with controversial relations to other theropods. Its derived members, the Megaraptoridae are noted for their large hand claws and robust forelimbs, which are usually reduced in size in other large theropods.

<i>Austrocheirus</i> Genus of reptiles (fossil)

Austrocheirus is an extinct genus of theropod dinosaur that lived during the Late Cretaceous period. It was named and described by Martin Ezcurra, Federico Agnolin and Fernando Novas in 2010. It contains the type species Austrocheirus isasii. The generic name means "southern hand". The specific epithet honours discoverer and preparator Marcelo Pablo Isasi.

The Cerro Fortaleza Formation, in older literature described as Pari Aike Formation, is a Late Cretaceous geologic formation of Campanian to Maastrichtian age of the Austral Basin in southern Patagonia, Argentina.

<i>Siats</i> Extinct genus of theropod dinosaur

Siats (/see-ats/) is an extinct genus of large theropod dinosaur known from the Late Cretaceous Cedar Mountain Formation of Utah, United States. It contains a single species, Siats meekerorum. It was initially classified as a megaraptoran, a clade of large theropods with very controversial relationships. Siats may be a neovenatorid allosauroid, a coelurosaur of uncertain phylogenetic position, or a tyrannosauroid.

<i>Murusraptor</i> Extinct genus of dinosaurs

Murusraptor is a genus of carnivorous megaraptoran theropod dinosaur from the Sierra Barrosa Formation, part of the Neuquén Group of Patagonia, in Argentina, South America. It is known from a single specimen that consists of a partial skull, ribs, partial pelvis, leg and other assorted skeletal elements.

Martín Dário Ezcurra is an Argentine palaeontologist naming many extinct genera such as Aerotitan, Lophostropheus and Powellvenator.

Tralkasaurus is a genus of abelisaurid dinosaur from the Huincul Formation from Río Negro Province in Argentina. The type and only species is Tralkasaurus cuyi, named in 2020 by Mauricio Cerroni and colleagues based on an incomplete skeleton. A medium-sized abelisaurid, Tralkasaurus exhibits a conflicting blend of characteristics found among the early-diverging abelisauroids with others that characterize the highly specialized clade Brachyrostra, and thus its position within the clade is poorly-resolved.

<i>Maip</i> Genus of megaraptoran dinosaurs

Maip is a genus of large megaraptorid theropod dinosaur from the Late Cretaceous (Maastrichtian) Chorrillo Formation of Santa Cruz, Argentina. The genus contains a single species, M. macrothorax, known from an incomplete, disarticulated skeleton. Maip may represent the largest megaraptorid known from South America, and possibly the world.

References

  1. 1 2 3 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. doi:10.1007/s00114-009-0614-x. PMID   19826771. S2CID   22646156.
  2. 1 2 3 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. hdl: 11336/12129 .
  3. 1 2 3 4 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.
  4. Rolando, Alexis M. A.; Motta, Matias J.; Agnolín, Federico L.; Manabe, Makoto; Tsuihiji, Takanobu; Novas, Fernando E. (2022-04-26). "A large Megaraptoridae (Theropoda: Coelurosauria) from Upper Cretaceous (Maastrichtian) of Patagonia, Argentina". Scientific Reports. 12 (1): Article number 6318. doi: 10.1038/s41598-022-09272-z . PMC   9042913 . PMID   35474310.
  5. Paul, G. S. (2010). The Princeton Field Guide to Dinosaurs . Princeton University Press. p.  99.
  6. 1 2 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.cretres.2013.04.001. hdl: 11336/102037 .
  7. Apesteguía, Sebastián; Smith, Nathan D.; Juárez Valieri, Rubén; Makovicky, Peter J. (2016). "An Unusual New Theropod with a Didactyl Manus from the Upper Cretaceous of Patagonia, Argentina". PLOS ONE. 11 (7): e0157793. Bibcode:2016PLoSO..1157793A. doi: 10.1371/journal.pone.0157793 . PMC   4943716 . PMID   27410683.
  8. 1 2 3 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 .
  9. 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. Bibcode:2014PLoSO...9j4800S. doi: 10.1371/journal.pone.0104800 . PMC   4139311 . PMID   25141301.
  10. 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. Bibcode:2014NatSR...4E6196L. doi:10.1038/srep06196. PMC   5385829 . PMID   25186586.
  11. Sickmann, Zachary T.; Schwartz, Theresa M.; Graham, Stephan A. (2018). "Refining stratigraphy and tectonic history using detrital zircon maximum depositional age: an example from the Cerro Fortaleza Formation, Austral Basin, southern Patagonia". Basin Research. 30 (4): 708–729. doi:10.1111/bre.12272.