Deinonychosauria

Bilateria

Deinonychosaurs Temporal range: Middle Jurassic-Late Cretaceous, 167–65.5 Ma PreЄ Є O S D C P T J K Pg N
Mounted Deinonychus antirrhopus skeleton, Field Museum of Natural History
Scientific classification
Phylum:	Chordata
Class:	Reptilia
Superorder:	Dinosauria
Order:	Saurischia
Suborder:	Theropoda
Apomorphy:	Aviremigia
Branch:	Paraves
Infraorder:	†Deinonychosauria Colbert & Russell, 1969
Subgroups
†Archaeopterygidae †Dromaeosauroidea †Troodontoidea

The Deinonychosauria ("fearsome claw lizards") were a successful clade of theropods in the Late Jurassic and Cretaceous Periods. These omnivores and carnivores are known for their switchblade-like second toe claws. The clade has been divided into two further clades — Dromaeosauridae and Troodontidae. The largest known of these was Utahraptor (7 m or 23 ft), and Anchiornis was the smallest (34 cm or 13 in).

Description

Like other theropods, deinonychosaurs were bipedal; that is, they walked on their hind legs. However, whereas most theropods walked with three toes contacting the ground, fossilized footprint tracks confirm that most deinonychosaurs held the second toe off the ground in a hyperextended position, with only the third and fourth toes bearing the weight of the animal. This is called functional didactyly.^[1] The enlarged second toe bore an unusually large, curved sickle-shaped claw (held off the ground or 'retracted' when walking), which is thought to have been used in capturing prey and climbing trees. This claw was especially blade-like in the large-bodied predatory eudromaeosaurs.^[2] One eudromaeosaur species, Balaur bondoc, also possessed a first toe which was highly modified in parallel with the second. Both the first and second toes on each foot of B. bondoc were also held retracted and bore enlarged, sickle-shaped claws.^[3]

Classification

• Infraorder Deinonychosauria
  • Euronychodon?
  • Pamparaptor
  • Paronychodon?
  • Family Archaeopterygidae?^[4]
  • Superfamiliy Dromaeosauroidea
    • Family Dromaeosauridae
      • Subfamily Microraptorinae
      • Subfamily Unenlagiinae
      • Node Eudromaeosauria
        • Subfamily Dromaeosaurinae
        • Subfamily Saurornitholestinae
        • Subfamily Velociraptorinae
  • Superfamily Troodontoidea
    • Family Troodontidae
      •  ?Subfamily Elopteryginae
      • Subfamily Troodontinae

References

1. ^ Li, Rihui; Lockley, M.G., Makovicky, P.J., Matsukawa, M., Norell, M.A., Harris, J.D. and Liu, M. (2007). "Behavioral and faunal implications of Early Cretaceous deinonychosaur trackways from China". Naturwissenschaften 95 (3): 185–91. doi:10.1007/s00114-007-0310-7. PMID 17952398. http://www.springerlink.com/content/v1u455854212404r/. 
2. ^ Longrich, N.R.; Currie, P.J. (2009). "A microraptorine (Dinosauria–Dromaeosauridae) from the Late Cretaceous of North America". PNAS 106 (13): 5002–7. doi:10.1073/pnas.0811664106. PMC 2664043. PMID 19289829. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2664043. 
3. ^ Z., Csiki; Vremir, M.; Brusatte, S. L.; and Norell, M. A. (in press). "An aberrant island-dwelling theropod dinosaur from the Late Cretaceous of Romania". Proceedings of the National Academy of Sciences of the United States of America preprint (35): 15357–61. doi:10.1073/pnas.1006970107. PMC 2932599. PMID 20805514. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2932599.  Supporting Information
4. ^ Xing Xu, Hailu You, Kai Du and Fenglu Han (28 July 2011). "An Archaeopteryx-like theropod from China and the origin of Avialae". Nature 475 (7357): 465–470. doi:10.1038/nature10288. PMID 21796204. http://www.nature.com/nature/journal/v475/n7357/full/nature10288.html. 

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