Megaraptor

Megaraptor
Temporal range: Late Cretaceous,[1] 91–88 Ma
↓
Claw cast with a ruler for scale
Scientific classification
Kingdom:Animalia
Phylum:Chordata
Clade:Dinosauria
Order:Saurischia
Suborder:Theropoda
Clade:†Megaraptora
Family:†Megaraptoridae
Genus:†Megaraptor
Novas, 1998
Species: †M. namunhuaiquii
Binomial name
Megaraptor namunhuaiquii
Novas, 1998

Megaraptor ("giant thief") is a genus of large theropod dinosaur that lived in the Turonian to Coniacian ages of the Late Cretaceous.[2][3] Its fossils have been discovered in the Patagonian region of Argentina. 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.[4]

Description

Megaraptor head reconstruction based on the juvenile skull

Megaraptor was initially described as a giant dromaeosaur, known primarily from a single claw (about 30 cm long) that resembled the sickle-shaped foot claw of dromaeosaurids.[2] The discovery of a complete front limb, however, showed that this giant claw actually came from the first finger of the hand. In 2010, Gregory S. Paul estimated its length at 8 metres (26 ft), its weight at 1 tonne (2,200 lbs).[5] The hands were unusually elongated, bearing sickle-shaped claws even more recurved than those of spinosaurids.[6]

Classification

The hand is quite distinct from other basal tetanurans, so it was not initially clear whether Megaraptor was an allosaurid, a carcharodontosaurid, a spinosauroid, or something else entirely.[3] Subsequent studies, as well as the identification of close relatives with similar large claws on the forelimbs (see below), helped identify Megaraptor as a highly advanced and lightly built allosauroid, and a member of the family Neovenatoridae.[7] More recent studies have proposed that Megaraptor and its kin are actually tyrannosauroids[8] or spinosauroids[9] as opposed to allosauroids.[8] A juvenile specimen described in 2014 has provided more evidence towards Megaraptor being a primitive tyrannosauroid.[10] The discovery of Gualicho indicates that Megaraptor may not be a tyrannosauroid, but either an allosauroid or basal coelurosaur.[11]

When first discovered and prior to publication, the spinosaurid Baryonyx was also reported to be a dromaeosaurid, and the allosauroid Chilantaisaurus was reported to be a possible spinosaurid, both based on the large hand claws.

Restored hand

The cladogram shown below follows an analysis by Porfiri et al., 2014.[12]

Megaraptora

 

Fukuiraptor

 
Megaraptoridae

 

Australovenator

 
 

Aerosteon

 
unnamed

Orkoraptor

 
 

Eotyrannus

 
 

Megaraptor

 
 
 

References

  1. ↑ Holtz, Thomas R. Jr. (2012) Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages, Winter 2011 Appendix.
  2. 1 2 Novas, F.E. (1998). "Megaraptor namunhuaiquii, gen. et sp. nov., a large-clawed, Late Cretaceous theropod from Patagonia". Journal of Vertebrate Paleontology. 18: 4–9. doi:10.1080/02724634.1998.10011030.
  3. 1 2 Calvo, J. O.; Porfiri, J.D.; Veralli, C.; Novas, F.E.; Poblete, F. (2004). "Phylogenetic status of Megaraptor namunhuaiquii Novas based on a new specimen from Neuquén, Patagonia, Argentina". Ameghiniana. 41: 565–575.
  4. ↑ https://www.paleowire.com/just-out-a-new-megaraptoran-theropod-dinosaur-from-the-upper-cretaceous-bajo-de-la-carpa-formation-of-northwestern-patagonia-cretaceous-research/
  5. ↑ Paul, G.S., 2010, The Princeton Field Guide to Dinosaurs, Princeton University Press p. 99
  6. ↑ Calvo, J.O., Porfiri, J.D., González-Riga, B.J., and Kellner, A.W. (2007) "A new Cretaceous terrestrial ecosystem from Gondwana with the description of a new sauropod dinosaur". Anais Academia Brasileira Ciencia, 79(3): 529-41.
  7. ↑ 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.
  8. 1 2 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.
  9. ↑ Holtz, T.R. Jr. (2012). Dinosaurs: The Most Complete, Up-to-date Encyclopedia for Dinosaur Lovers of All Ages. Random House Books for Young Readers. pp. 95–96. ISBN 978-0-375-82419-7.
  10. ↑ Porfiri, J. D., Novas, F. E., Calvo, J. O., Agnolín, F. L., Ezcurra, M. D. & Cerda, I. A.; Novas; Calvo; Agnolín; Ezcurra; 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.
  11. ↑ http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0157793
  12. ↑ Juan D. Porfiri; Fernando E. Novas; Jorge O. Calvo; Federico L. Agnolín; Martín D. Ezcurra; 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.
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