Megaraptora

Megaraptorans Temporal range: Early Cretaceous - Late Cretaceous, 130–84 Ma PreЄ Є O S D C P T J K Pg N
Megaraptor claw cast with a ruler for scale.
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Clade:	Dinosauria
Order:	Saurischia
Suborder:	Theropoda
Clade:	Avetheropoda
Clade:	†Megaraptora Benson, Carrano & Brusatte, 2010
Subgroups
†Chilantaisaurus? †Fukuiraptor †Siats †Megaraptoridae †Aerosteon †Australovenator †Megaraptor †Orkoraptor †Rapator

Megaraptora is a group of large carnivorous theropod dinosaurs with controversial relationships. Phylogenetic studies conducted by Benson, Carrano and Brusatte (2010) and Carrano, Benson and Sampson (2012) recovered the group as a branch of the allosauroids (specifically within the family Neovenatoridae), part of a large group of carnosaurs that also includes the metriacanthosaurids, carcharodontosaurids, and allosaurids. This would make megaraptorans the last surviving allosauroids; at least a few megaraptorans, including Orkoraptor, lived near the end of the Mesozoic era, dating to the late Santonian stage of the late Cretaceous period, about 84 million years ago.^[1][2] On the other hand, Novas et al. (2012), while confirming that Neovenator was closely related to carcharodontosaurids, simultaneously found Megaraptor and related genera to probably be coelurosaurs closely related to tyrannosaurids.^[3] A juvenile specimen of Megaraptor suggests it to be within Tyrannosauroidea, as well.^[4] From these debated relations, megaraptorans have been, at the moment, simply placed by some under avetheropods, mostly to remain neutral between carnosaurs and coelurosaurs.

Though it is unknown as of yet where they stand in relation to other theropods, the origins of megaraptorids have recently been determined. Studies by paleontologists Phil Bell, Steve Salisbury et al of a newly discovered, as-yet-unnamed megaraptorid (referred to by the public media as "Lightning Claw," and most likely synonymous with Rapator) from opal fields southwest of Lightning Ridge, Australia, dating back 110 million years ago reveals that megaraptorids likely evolved in Australia, then spread to the rest of Gondwana in an episode of evolutionary radiation. The specimen also allowed for alternative phylogenitic testing as to the placement of megaraptorans as either tyrannosauroids or carcharodontosaurids.^[5][6]

Classification

The cladogram below follows the 2010 analysis by Benson, Carrano and Brusatte.^[1] Another study published later in 2010 found the Australian theropod Rapator to be a megaraptoran extremely similar to Australovenator,^[7] and the description of Siats also recovered it as a megaraptoran.^[8]

Neovenatoridae	Neovenator unnamed Chilantaisaurus Megaraptora unnamed Australovenator Fukuiraptor ?Orkoraptor unnamed Aerosteon Megaraptor

This cladogram shown below follows an analysis by Porfiri et al., 2014,^[9] which recovers Eotyrannus as a megaraptoran;

Megaraptora	Fukuiraptor Megaraptoridae Australovenator Aerosteon unnamed Orkoraptor Eotyrannus Megaraptor

References

1. 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.
2. Matthew T. Carrano, Roger B. J. Benson and Scott D. Sampson (2012). "The phylogeny of Tetanurae (Dinosauria: Theropoda)". Journal of Systematic Palaeontology 10 (2): 211–300. doi:10.1080/14772019.2011.630927.
3. F. E. Novas, F. L. Agnolín, M. D. Ezcurra, J. I. Canale, J. D. Porfiri (2012). "Megaraptorans as members of an unexpected evolutionary radiation of tyrant-reptiles in Gondwana". Ameghiniana 49 (Suppl.): R33.
4. Porfiri, J. D., Novas, F. E., Calvo, J. O., Agnolín, F. L., Ezcurra, M. D. & Cerda, I. 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.
5. Bell, P. R., Cau, A., Fanti, F., & Smith, E. (2015). A large-clawed theropod (Dinosauria: Tetanurae) from the Lower Cretaceous of Australia and the Gondwanan origin of megaraptorid theropods. Gondwana Research.
6. New dinosaur is Australia’s largest carnivore Australian Geographic.
7. Agnolin, Ezcurra; Pais; Salisbury (2010). "A reappraisal of the Cretaceous non-avian dinosaur faunas from Australia and New Zealand: Evidence for their Gondwanan affinities". Journal of Systematic Palaeontology 8 (2): 257–300. doi:10.1080/14772011003594870.
8. Zanno, L. E.; Makovicky, P. J. (2013). "Neovenatorid theropods are apex predators in the Late Cretaceous of North America". Nature Communications 4: 2827. Bibcode:2013NatCo...4E2827Z. doi:10.1038/ncomms3827. PMID 24264527.
9. Juan D. Porfiri, Fernando E. Novas, Jorge O. Calvo, Federico L. Agnolín, Martín D. Ezcurra and Ignacio A. Cerda (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.