Orkoraptor

Orkoraptor Temporal range: Cenomanian–Santonian PreЄ Є O S D C P T J K Pg N
Artist's restoration
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Clade:	Dinosauria
Order:	Saurischia
Suborder:	Theropoda
Clade:	Avetheropoda
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. Found in the Pari Aike Formation of Southern Patagonia, it is one of the southernmost carnivorous dinosaurs known from South America.

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.

Description

Orkoraptor was a medium-sized theropod. In 2010, Gregory S. Paul estimated its length as 6 meters and mass as 500 kilograms.

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. 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.

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, or merely an alternative name for the Cerro Fortaleza Formation. 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. 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.