Deinonychus
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2008-07-14T09:57:52Z
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:''This article is about the dinosaur. For the Dutch doom metal group see [[Deinonychus (band)]].''
{{Taxobox
| name = ''Deinonychus''
| fossil_range = [[Early Cretaceous]]
| image = Deinonychus skeleton FMNH.jpg
| image_width = 250px
| image_caption = ''Deinonychus antirrhopus'' skeleton
| regnum = [[Animal]]ia
| phylum = [[Chordate|Chordata]]
| classis = [[Reptile|Sauropsida]]
| superordo = [[Dinosaur]]ia
| ordo = [[Saurischia]]
| subordo = [[Theropoda]]
| familia = [[Dromaeosauridae]]
| genus = '''''Deinonychus'''''
| genus_authority = [[John Ostrom|Ostrom]], 1969
| subdivision_ranks = [[Species]]
| subdivision =
* '''''D. antirrhopus''''' <small>([[Type (zoology)|type]])</small><br/><small>Ostrom, 1969</small>
}}
'''''Deinonychus''''' ({{pronEng|daɪˈnɒnikəs}}) ([[Ancient Greek|Greek]] ''δεινος'', 'terrible' and ''ονυξ/ονυχος'', 'claw') was a [[genus]] of [[carnivore|carnivorous]] [[dromaeosauridae|dromaeosaurid]] [[dinosaur]]. There is one described species, ''Deinonychus antirrhopus''. This 3.4 metre (11 ft) long dinosaur lived during the early [[Cretaceous]] [[Period (geology)|Period]] ([[Aptian]] - [[Albian]] [[faunal stage|stages]], 121 to 98.9 [[Mya (unit)|million years ago]]). Fossils have been recovered from the [[U.S. state]]s of [[Montana]], [[Wyoming]] and [[Oklahoma]], though teeth that may belong to ''Deinonychus'' have been found much farther east in [[Maryland]].
“Terrible claw” refers to the unusually large, sickle-shaped talon on the second toe of each hind foot, which was probably held up off the ground while the dinosaur walked on the third and fourth toes. It was commonly thought that ''Deinonychus'' would kick with the sickle claw to slash at its prey but recent tests on reconstructions of similar ''[[Velociraptor]]'' talons suggest that the claw was used to stab, not slash. The species name ''antirrhopus'' means “counter balance”, which refers to John Ostrom's idea about the function of the tail. As in other dromaeosaurids, the tail vertebrae have a series of ossified tendons and super - elongated bone [[Process (anatomy)|processes]]. These features seemed to make the tail into a stiff counterbalance, but a fossil of the very closely related ''Velociraptor mongoliensis (IGM'' 100/986) has an articulated tail skeleton that is curved laterally in a long S – shape. This suggests that, in life, the tail could swish to the sides with a high degree of flexibility<ref name=norellmakovicky1999>{{cite_journal |last=Norell |first=Mark A. |coauthors=& Makovicky, Peter J. |year=1999 |title=Important features of the dromaeosaurid skeleton II: information from newly collected specimens of ''Velociraptor mongoliensis'' |journal=American Museum Novitates |volume=3282 |pages=1–45 |url=http://hdl.handle.net/2246/3025}}</ref> In both the Cloverly and Antlers Formation, ''Deinonychus'' remains have been found closely associated with those of the ornithopod ''[[Tenontosaurus]]''. Teeth discovered associated with ''Tenontosaurus'' specimens imply it was hunted or at least scavenged upon by ''Deinonychus''.
[[Paleontology|Paleontologist]] [[John Ostrom]]'s study of ''Deinonychus'' in the late 1960s [[Dinosaur renaissance|revolutionized]] the way scientists thought about dinosaurs, igniting the debate on whether or not dinosaurs were warm-blooded. Before this, the popular conception of dinosaurs had been one of plodding, reptilian giants. Ostrom noted lightweight bones and raptorial claws on the feet, which revealed an active, agile predator.
==Description==
[[Image:Deinonychus-scale.png|left|thumb|Size comparison of ''Deinonychus'' with a human.]]Based on the largest known specimens, ''Deinonychus'' could reach 3.4 meters (11.1 ft), with a maximum skull length of 410 mm (16.4 [[inch|in]]), a hip height of 0.87 meters (2.85 ft), a maximum weight of 73 kilograms (161 [[Pound (mass)|lb]]).<ref name=paul1988b>{{cite book|last=Paul |first=G.S. |year=1988 |title=Predatory Dinosaurs of the World |location=New York |publisher=Simon and Schuster |pages=366-369 }}</ref> Its skull was equipped with powerful jaws lined with around sixty curved, blade-like teeth. Studies of the skull have progressed a great deal over the decades. Ostrom reconstructed the partial, imperfectly preserved, skulls that he had as triangular, broad, and fairly similar to ''[[Allosaurus]]''. Additional ''Deinonychus'' skull material and closely related species found with good 3D preservation<ref name=MaxwellWitmer1996>{{cite_journal |last=Maxwell |first=W.D. |coauthors=&Witmer, L.M. |year=1996 |title= New Material of ''Deinonychus'' (Dinosauria, Theropoda)|journal= Journal of Vertebrate Paleontology volume=16(3) |pages=51A }}</ref> show that the palate was more vaulted than Ostrom thought, making the snout far narrower, while the jugals flared broadly, giving greater stereoscopic vision. The skull of ''Deinonychus'' was different from that of ''Velociraptor'', however, in that it had a more robust skull roof like that of ''[[Dromaeosaurus]]'', and did not have the depressed nasals of ''Velociraptor''.<ref name="Witmer96">Witmer, Lawrence M., Maxwell, William D. (1996). " The skull of ''Deinonychus'' (Dinosauria:Theropoda): New insights and implications". ''Journal of Vertebrate Paleontology'',16(3): 73A</ref> Both the skull and the lower jaw had [[fenestra]]e (skull openings) which reduced the weight of the skull. In ''Deinonychus'', the [[antorbital fenestra]], a skull opening between the eye and nostril, was particularly large.<ref name=MaxwellWitmer1996/>
Like all dromaeosaurs, ''Deinonychus'' possessed large hands ([[Manus (zoology)|manus]]) with three claws on each forelimb. The first digit was shortest and the second was longest. Each hind foot bore a sickle-shaped claw on the second digit, which was probably used during predation.
==Classification==
''Deinonychus'' is one of the best-known [[dromaeosauridae|dromaeosaurids]],<ref name ="dinosauria04">{{cite book|title=The Dinosauria |edition=2nd edition |year=2004 |chapter= Dromaeosauridae |editor=Weishampel, D.B., Dodson, P., Osmólska, H. |author=Norell, M.A., Makovicky, P.J. |pages=196-210| location=Berkeley|publisher=University of California Press|isbn= 0-520-24209-2}}</ref> and is a close relative of the smaller ''[[Velociraptor]]'', found in younger, Late Cretaceous-age rock formations in Central Asia.<ref name="norelletal06">{{cite journal| last=Norell |first=M.A. |coauthors=Clark, J.M., Turner, A.H., Makovicky, P.J., Barsbold, R., and Rowe, T.|year=2006|title=A new dromaeosaurid theropod from Ukhaa Tolgod (Ömnögov, Mongolia) |journal=American Museum Novitates |volume=3545 |pages=1–51 |url=http://digitallibrary.amnh.org/dspace/bitstream/2246/5823/1/N3545.pdf |accessdate=2007-07-07|doi=10.1206/0003-0082(2006)3545[1:ANDTFU]2.0.CO;2}}</ref><ref name=THN07>{{cite journal |last=Turner |first=A.S. |coauthors=Hwang, S.H.; and Norell, M.A. |year=2007 |title=A small derived theropod from Öösh, Early Cretaceous, Baykhangor Mongolia |journal=American Museum Novitates |volume=3557 |pages=1–27 |url=http://digitallibrary.amnh.org/dspace/bitstream/2246/5845/1/N3557.pdf |accessdate=2007-03-29 |doi=10.1206/0003-0082(2007)3557[1:ASDTFS]2.0.CO;2}}</ref> The [[clade]] they form is called Velociraptorinae. The subfamily name Velociraptorinae was first coined by [[Rinchen Barsbold]] in 1983<ref>{{cite journal|last = Barsbold |first = R. |year = 1983 |title = Carnivorous Dinosaurs from the Cretaceous of Mongolia |journal = The Joint Soviet-Mongolian Palaeontological Expedition, Transactions | volume = 19| pages =1–117}}</ref> and originally contained the single genus ''Velociraptor''. Later [[Phil Currie]] included most of the dromaeosaurids.<ref name="currie">{{cite journal |last=Currie |first=P. J. |year=1995 |title=New information on the anatomy and relationships of ''Dromaeosaurus albertensis'' (Dinosauria: Theropoda) |journal=Journal of Vertebrate Paleontology |volume=15 |issue=3 |pages=576–591}} ([https://www.vertpaleo.org/publications/jvp/15-576-591.cfm abstract])</ref> Two Late Cretaceous genera, ''[[Tsaagan]]'' from Mongolia<ref name="norelletal06"/> and the North American ''[[Saurornitholestes]]'',<ref name=paul1988b/> may also be close relatives, but the latter is poorly known and hard to classify.<ref name="norelletal06"/> ''Velociraptor'' and its allies are regarded as using their claws more than their skulls as killing tools, as opposed to dromaeosaurids like ''[[Dromaeosaurus]]'' with stockier skulls.<ref name=paul1988>{{cite book|last=Paul|first=G.S.|year=1988|title=Predatory dinosaurs of the world : a complete illustrated guide|location=New York|publisher=Simon and Schuster|pages=p. 358| isbn=0-671-61946-2}}</ref> Together with the [[Troodontidae|troodontids]], the dromaeosaurids form the [[Deinonychosauria]] clade which is a sister taxon of [[birds|aves]]. Phylogenetically, the Deinonychosauria represent the group of non-avian dinosaurs the most closely related to birds.<ref name="Benton">{{cite book| last =Benton| first =M.J.| authorlink =| coauthors =| title =Vertebrate Palaeontology (Third Edition)| publisher =Blackwell Publishing| date =2004| location =| pages =472| url =http://palaeo.gly.bris.ac.uk/benton/vertclass.html| doi =| id = | isbn =9780632056378}}</ref>
==Discovery and naming==
[[Image:Deinonychus BW.jpg|thumb|Illustration of ''Deinonychus antirrhopus'']]
Fossilized remains of ''Deinonychus'' have been recovered from the [[Cloverly Formation]] of [[Montana]] and [[Wyoming]]<ref name = "ostrom1970">{{cite journal|last=Ostrom|first=J. H.|year=1970|title=Stratigraphy and paleontology of the Cloverly Formation(Lower Cretaceous) of the Bighorn Basin area, Wyoming and Montana |journal=Bulletin of the Peabody Museum of Natural History|volume=35|pages=1–234}}</ref> and in the [[Antlers Formation]] of [[Oklahoma]],<ref name ="brinkman1998"> {{cite journal|last=Brinkman|first=D. L.|coauthors=R. L. Cifelli, and N. J. Czaplewski |year=1998 |title=First occurrence of ''Deinonychus antirrhopus'' (Dinosauria: Theropoda) from the Antlers Formation (Lower Cretaceous: Aptian-Albian) of Oklahoma |journal=Oklahoma Geological Survey Bulletin|volume=146|pages=1–27}}</ref> in [[North America]]. Additionally, teeth found in the Arundel Clay Facies (Aptian), of the [[Potomac Formation]] on the [[Atlantic Coastal Plain]] of [[Maryland]] may be assigned to the genus.<ref>{{cite book|last=Lipka|first=T. R. |year=1998 |chapter=The Affinities of the Enigmatic Theropods of the Arundel Clay Facies (Aptian), Potomac Formation, Atlantic Coastal Plain of Maryland |title=Lower and Middle Cretaceous Terrestrial Ecosystems| editor=Lucas, S.G., Kirkland, J.I. and Estep, J.W.|publisher= New Mexico Museum of Natural History and Science |location=Albuquerque |series=New Mexico Museum of Natural History and Science Bulletin, 14|pages=229-234| oclc=40283894}}</ref>
The first remains were uncovered in 1931 in southern [[Montana]] near the town of [[Bridger, Montana|Bridger]]. The team leader, paleontologist [[Barnum Brown]], was primarily concerned with excavating and preparing the remains of the [[ornithopod]] dinosaur ''[[Tenontosaurus]]'', but in his field report from the dig site to the [[American Museum of Natural History]], he reported the discovery of a small carnivorous dinosaur close to a ''Tenontosaurus'' skeleton, "but encased in lime difficult to prepare."<ref name="grellet-tinner&makovicky2006">{{cite journal|last=Grellet-Tinner|first=G.|coauthors=and Makovicky, P. |year=2006 |title=A possible egg of the dromaeosaur ''Deinonychus antirrhopus'': phylogenetic and biological implications |journal=Canadian Journal of Earth Sciences |volume=43 |issue=6 |pages=705–719 |doi=10.1139/E06-033}}</ref> He informally called the animal "Daptosaurus" and made preparations for describing it and having the skeleton put on display, but never finished this work.<ref name=NGD95>{{cite book |last=Norell |first=M. A. |coauthors=Gaffney, E. S.; and Dingus, L. |title=Discovering Dinosaurs in the American Museum of Natural History |publisher=Knopf |location=New York |year=1995 |pages=126-130 |isbn=0-679-43386-4}}</ref> Brown brought back from the Cloverly Formation the skeleton of a smaller theropod with seemingly oversized teeth that he informally named "Megadontosaurus". [[John Ostrom]], reviewing this material decades later, realized that the teeth came from ''Deinonychus'', but the skeleton came from a completely different animal. He named this skeleton ''[[Microvenator]]''.<ref name=NGD95/>
A little more than thirty years later, in August 1964, paleontologist John Ostrom led an expedition from Yale University’s Peabody Museum which discovered more skeletal material. Expeditions during the following two summers uncovered more than 1000 bones, among which were at least three individuals. Since the association between the various recovered bones was weak, making the exact number of individual animals represented impossible to determine properly, the [[Type (zoology)|type]] specimen (YPM 5205) of ''Deinonychus'' was restricted to the complete left foot and partial right foot that definitely belonged to the same individual.<ref name="ostrom1969"/> The remaining specimens were catalogued in fifty separate entries at [[Yale University|Yale]]'s [[Peabody Museum of Natural History]].
Later study by Ostrom and Grant E. Meyer analyzed their own material as well as Brown's "Daptosaurus" in detail and found them to be the same species. Ostrom published his findings in 1969, giving all the referred remains the new name of ''Deinonychus antirrhopus''.<ref name="ostrom1969">{{cite journal|last=Ostrom|first=J. H.|year=1969|title=Osteology of ''Deinonychus antirrhopus'', an unusual theropod from the Lower Cretaceous of Montana |journal=Peabody Museum of Natural History Bulletin |volume=30 |pages=1–165}}</ref> "''antirrhopus''" means "counterbalancing" and refers to the likely purpose of a stiffened tail.
Though a myriad of bones was available by 1969, many important ones were missing or hard to interpret. There were few postorbital skull elements, no femurs, no sacrum, no furcula or sternum, missing vertebrae, and (Ostrom thought) only a tiny fragment of a coracoid. Ostrom’s skeletal reconstruction of ''Deinonychus'' included a very unusual pelvic bone – a pubis which was trapezoidal and flat, unlike that of other theropods, but which was the same length as the ischium and which was found right next to it.
===Further findings===
In 1974 Ostrom published another monograph on the shoulder of ''Deinonychus'' in which he realized that the pubis that he had described was actually a coracoid – a shoulder element.<ref name="Ostrom74">Ostrom, John H.,. (1974). " The Pectoral Girdle and Forelimb Function of Deinonychus (Reptilia: Saurischia) : A Correction". '' Postilla, Peabody Museum of Natural History Bulletin '', 165:1-11.</ref> In that same year, another specimen of ''Deinonychus'' was excavated in Montana by a Harvard University expedition headed by Farish Jenkins. This discovery added several new elements; well preserved femurs, pubes, a sacrum, and better ilia, as well as elements of the pes and metatarsus. Ostrom described this specimen and revised his skeletal restoration of ''Deinonychus''. This time it showed the very long pubes, and Ostrom began to suspect that they may have even been a little retroverted like those of birds.<ref name=”ostrom 1976”>{{cite journal|last=Ostrom|first=J.H. |year=1976 |title= On a new specimen of the Lower Cretaceous theropod dinosaur Deinonychus antirrhopus |journal=Breviora|volume=439 |pages=1–21}}</ref>
A skeleton of ''Deinonychus'' including bones from the original (and most complete) specimen can be seen on display at the American Museum of Natural History,<ref>{{cite web | author = American Museum of Natural History | title = Deinonychus | work = http://www.amnh.org | publisher = American Museum of Natural History | date = 2007 | url = http://www.amnh.org/exhibitions/expeditions/treasure_fossil/Fossils/Specimens/deinonychus.html
| accessdate = 2007-07-13}}</ref> with another specimen on display at the [[Museum of Comparative Zoology]] at [[Harvard University]]. The American Museum and Harvard specimens are from a different locality than the Yale specimens. Even these two skeletal mounts are lacking elements including the sterna, sternal ribs, furcula, and gastralia.
Even after all of Ostrom’s work, several small blocks of lime-encased material remained unprepared in storage at the American Museum. These consisted mostly of isolated bones and bone fragments, including the original matrix, or surrounding rock in which the specimens were initially buried. An examination of these unprepared blocks by Gerald Grellet-Tinner and Peter Makovicky in 2000 revealed an interesting, overlooked feature. Several long, thin bones identified on the blocks as ossified tendons (structures which helped stiffen the tail of ''Deinonychus'') turned out to actually represent [[Gastralium|gastralia]] (abdominal ribs). More significantly, a large number of previously unnoticed fossilized eggshells were discovered in the rock matrix which had surrounded the original ''Deinonychus'' specimen.<ref name="makovicky&grellet-tinner2000">{{cite book|last=Makovicky|first=P. J. |coauthors= Grellet-Tinner, G. |year=2000 |chapter=Association between a specimen of ''Deinonychus antirrhopus'' and theropod eggshell |editor= Bravo, A.M. and T. Reyes|title= First international symposium on dinosaur eggs and babies,Isona i Conca Dellà Catalonia, Spain, 23–26 September 1999| pages=123–128}}</ref>
In a subsequent, more detailed report on the eggshells, Grellet-Tinner and Makovicky concluded that the [[Egg (biology)|egg]] almost certainly belonged to ''Deinonychus'', representing the first dromaeosaurid egg to be identified.<ref name="grellet-tinner&makovicky2006"/> Moreover, the external surface of one eggshell was found in close contact with the gastralia suggesting that ''Deinonychus'' might have [[Avian incubation|brooded]] its eggs. This implies that ''Deinonychus'' used body heat transfer as a mechanism for egg incubation, and indicates an [[endothermy]] similar to modern birds.<ref>{{cite journal|last=Grellet-Tinner|first=Gerard|year=2006|title=Oology And The Evolution Of Thermophysiology In Saurischian Dinosaurs: Homeotherm And Endotherm Deinonychosaurians? |journal=Papeis Avulsos de Zoologia |volume=46 |issue=1 |pages=1–10| url=http://www.scielo.br/scielo.php?pid=S0031-10492006000100001&script=sci_arttext| accessdate=2007-07-07}}</ref> Further study by Gregory Erickson and colleagues finds that this individual was 13 or 14 years old at death and its growth had plateaued. Unlike other theropods in their study of specimens found associated with eggs or nests, it had finished growing at the time of its death.<ref name=GMEetal07>{{cite journal |last=Erickson |first=Gregory M. |authorlink=Gregory M. Erickson |coauthors=Curry Rogers, Kristina; Varricchio, David J.; Norell, Mark A.; and Xu, Xing |year=2007 |title=Growth patterns in brooding dinosaurs reveals the timing of sexual maturity in non-avian dinosaurs and genesis of the avian condition |journal=Biology Letters |volume=published online |url=http://www.journals.royalsoc.ac.uk/content/6508252h00612424/fulltext.pdf |format=pdf |doi=10.1098/rsbl.2007.0254 |accessdate=2007-07-26 |pages=558}}</ref>
===Implications===
[[Image:Archaeo-deinony hands.svg|thumb|right|The similarity of the forelimbs of ''Deinonychus'' (left) and ''[[Archaeopteryx]]'' (right) led [[John Ostrom]] to revive the link between dinosaurs and birds.]]
The description in 1969 by Ostrom of ''Deinonychus'' has been described as the most important single discovery of dinosaur paleontology in the mid 20th century.<ref name = "FasWeis04">{{cite book|author=Fastovsky, D.E., Weishampel, D.B. |title=The Evolution and Extinction of the Dinosaurs|edition= 2nd edition| year=2005 |chapter=Theropoda I: Nature Red in Tooth and Claw |editor=Fastovsky, D.E., Weishampel, D.B. |pages=265–299|location= Cambridge |publisher=Cambridge University Press|id=ISBN 0-521-81172-4}}</ref> The discovery of this clearly active, agile predator did much to change the scientific (and popular) conception of dinosaurs and opened the door to speculation that dinosaurs may have been [[warm-blooded]]. This development has been termed the [[Dinosaur renaissance]]. Several years later, Ostrom noted similarities between the forefeet of ''Deinonychus'' and that of birds, which observation led him to revive the hypothesis that birds are descended from dinosaurs.<ref name="ostrom1976b">{{cite journal|last=Ostrom|first=J. H. |year=1976 |title=''Archaeopteryx'' and the origin of birds |journal=Biological Journal of the Linnean Society |volume=8 |pages=91–182 |doi=10.1111/j.1095-8312.1976.tb00244.x}}</ref> Thirty years later, this idea is almost universally accepted.
''Deinonychus'' almost certainly was feathered, since its close relative ''[[Velociraptor]]'' was shown in 2007 to have been feathered, based on the presence of [[quill knob]]s on the forearm. Such knobs show where feathers anchor in modern birds. This recent discovery added weight to already strong theories that all [[dromaeosaurids]] were feathered.<ref name="turneretal2007b">{{cite journal |last=Turner |first=A.H. |coauthors=Makovicky, P.J.; and Norell, M.A. |year=2007 |title=Feather quill knobs in the dinosaur ''Velociraptor'' |journal=Science |volume=317 |issue=5845 |pages=1721|url=http://www.sciencemag.org/cgi/reprint/317/5845/1721.pdf |format=pdf |doi=10.1126/science.1145076 |pmid=17885130 }}</ref>
==Paleobiology and paleoecology==
Geological evidence suggests that ''Deinonychus'' inhabited a [[floodplain]] or [[swamp]]like habitat.<ref name ="dinosauria04"/> The paleoenvironment of both the Cloverly Formation and the [[Antlers Formation]], in which remains of ''Deinonychus'' have been found, consisted of forests, [[River delta|deltas]] and lagoons, not unlike today's [[Louisiana]].<ref name="wedel2005"/>
Other animals ''Deinonychus'' shared its world with include herbivorous dinosaurs such as the armoured ''[[Sauropelta]]'' and the ornithopods ''[[Zephyrosaurus]]'' and ''[[Tenontosaurus]]''. In Oklahoma, the ecosystem of ''Deinonychus'' also included the large theropod ''[[Acrocanthosaurus]]'', the huge sauropod ''[[Sauroposeidon]]'', the crocodilian ''[[Goniopholis]]'', and the [[gar]] ''[[Lepisosteus]]''.<ref name="wedel2005">{{cite journal|last=Wedel|first=M. J. |coauthors=Cifelli, R. L. |year=2005 |title=''Sauroposeidon'': Oklahoma’s Native Giant |journal=Oklahoma Geology Notes |volume=65| issue=2 |pages=40–57 |url=http://sauroposeidon.net/Wedel-Cifelli_2005_native-giant-plus-cover.pdf | accessdate=2007-07-07}}</ref>If the teeth found in Maryland are those of ''Deinonychus'', then its neighbors would include ''[[Astrodon]]'', ''[[Dryptosaurus]]'' and a nodosaur (called ''[[Priconodon]]'') only known from teeth.
===Predatory behavior===
[[Image:Deinonychus.jpg|thumb|left|Head of ''Deinonychus'' based on recent reconstruction of the skull.]]
''Deinonychus'' teeth found in association with fossils of the [[ornithopod]] dinosaur ''Tenontosaurus'' are quite common in the Cloverly Formation.
Two quarries have been discovered that preserve fairly complete ''Deinonychus'' fossils near ''Tenontosaurus'' fossils. The first, the Yale quarry in the Cloverly of Montana, includes numerous teeth, four adult ''Deinonychus'' and one juvenile ''Deinonychus''. The association of this number of ''Deinonychus'' [[skeleton]]s in a single quarry suggests that ''Deinonychus'' may have fed on that animal, and perhaps hunted it. Ostrom and Maxwell have even used this information to speculate that ''Deinonychus'' might have lived and hunted in packs.<ref name="maxwell&ostrom1995">{{cite journal|last=Maxwell|first=W. D. |coauthors=Ostrom, J.H. |year=1995 |title=Taphonomy and paleobiological implications of ''Tenontosaurus''-''Deinonychus'' associations|journal=Journal of Vertebrate Paleontology |volume=15 |issue=4 |pages=707–712}} ([http://www.vertpaleo.org/publications/jvp/15-707-712.cfm abstract])</ref> The second such quarry is from the Antlers formation of Oklahoma. The site contains six partial skeletons of ''Tenontosaurus'' of various sizes, along with one partial skeleton and many teeth of ''Deinonychus''. One tenontosaur humerus even bears what might be ''Deinonychus'' tooth marks. Brinkman ''et al''. (1998) point out that ''Deinonychus'' had an adult mass of 70-100 kilograms, whereas adult tenontosaurs were 1-4 metric tons. A solitary ''Deinonychus'' could not kill an adult tenontosaur, suggesting that pack hunting is possible.<ref name="Brinkmanetal1998">{{cite journal|last=Brinkman|first=Daniel L. |coauthors=Cifelli, Richard L., Czaplewski, Nicholas J. |year=1998 |title="First Occurrence of Deinonychus antirrhopus (Dinosauria: Theropoda) from the Antlers Formation (Lower Cretaceous: Aptain-Albian) of Oklahoma"|journal=Oklahoma Geological Survey |issue=164 |pages=27}}</ref>
A recent study by Roach and Brinkman has called into question the cooperative pack hunting behavior of ''Deinonychus'', based on what is known of modern carnivore hunting and the [[taphonomy]] of tenontosaur sites. Modern [[archosaur]]s ([[bird]]s and [[crocodile]]s) and [[komodo dragon]]s display little cooperative hunting; instead, they are usually either solitary hunters, or are drawn to previously-killed carcasses, where much conflict occurs between individuals of the same species. For example, in situations where groups of komodo dragons are eating together, the largest individuals eat first and will attack smaller komodos that attempt to feed; if the smaller animal is killed, it is [[cannibalism (zoology)|cannibalized]]. When this information is applied to the tenontosaur sites, it appears that what is found is consistent with ''Deinonychus'' having a komodo- or crocodile-like feeding strategy. ''Deinonychus'' skeletal remains found at these sites are from subadults, with missing parts consistent with having been eaten by other ''Deinonychus''.<ref>{{cite journal|last=Roach|first=B. T.|coauthors=D. L. Brinkman |year=2007 |title=A reevaluation of cooperative pack hunting and gregariousness in ''Deinonychus antirrhopus'' and other nonavian theropod dinosaurs|journal=Bulletin of the Peabody Museum of Natural History |volume=48 |issue=1 |pages=103–138 |doi=10.3374/0079-032X(2007)48[103:AROCPH]2.0.CO;2}}</ref>
====Limb function====
Despite being the most distinctive feature of ''Deinonychus'', the shape and curvature of the [[sickle]]-claw varies between specimens. The type specimen described by Ostrom in 1969 has a strongly curved sickle claw, while a newer specimen described in 1976 had a claw with much weaker curvature, more similar in profile with the 'normal' claws on the remaining toes.<ref name="ostrom1976">{{cite journal|last=Ostrom |first=J. H. |year=1976 |title=On a new specimen of the Lower Cretaceous theropod dinosaur ''Deinonychus antirrhopus'' |journal=Breviora |volume=439 |pages=1–21}}</ref> Ostrom suggested that this difference in the size and shape of the sickle claws could be due to individual, sexual, or age-related variation.
[[Image:Deinonychus-antirrhopus jconway.jpg|left|thumb|Illustration of ''Deinonychus antirrhopus'' at rest with forelimbs folded.<br> Plumage based on related genera.]]
Ostrom originally speculated that ''Deinonychus'' gripped its prey with the talons of the forelimbs while delivering disemboweling slashes with its sickle claws.<ref name ="ostrom1969"/> Later studies, however, have shown that the sickle claws were not used to slash but rather to deliver small stabs to the victim,<ref>{{cite journal |last=Carpenter |first=K. |year=1998| title=Evidence of predatory behavior by carnivorous dinosaurs |journal=Gaia |volume=15 |pages=135–144 |url=https://scientists.dmns.org/sites/kencarpenter/PDFs%20of%20publications/theropod%20predation.pdf |accessdate=2007-07-07}}</ref> possibly indicating their use as [[crampon]]-like climbing tools.<ref name="manning2006">{{cite journal |last=Manning |first=P. L. |coauthors=D. Payne, J. Pennicott, P. M. Barrett, and R. A. Ennos |year=2006 |title=Dinosaur killer claws or climbing crampons? |journal=Biology Letters |volume=2| issue=1 |pages=110–112| doi=10.1098/rsbl.2005.0395| pmid=17148340}}</ref> Biomechanical studies by [[Kenneth Carpenter|Ken Carpenter]] in 2002 confirmed that the most likely function of the forelimbs in predation was grasping, as their great lengths would have permitted longer reach than for most other theropods. The rather large and elongated [[coracoid]], hinting for powerful muscles in the forelimbs, further strengthened this interpretation.<ref>{{cite journal |last=Carpenter |first=K. |year=2002 |title=Forelimb biomechanics of nonavian theropod dinosaurs in predation |journal=Senckenbergiana Lethaea |volume=82 |pages=59–76| url=https://scientists.dmns.org/sites/kencarpenter/PDFs%20of%20publications/theropod%20forelimb.pdf |accessdate=2007-07-07}}</ref> Carpenter's biomechanical studies using bones casts also showed that ''Deinonychus'' could not fold its arms against its body like a bird ("avian folding"), contrary to what was inferred from the earlier 1985 descriptions by [[Jacques Gauthier]]<ref>{{cite conference |last=Gauthier |first=J. |coauthors=Padian, K. |year=1985 |title=Phylogenetic, Functional, And Aerodynamic Analyses Of The Origin Of Birds And Their Flight |editor=M.K. Hecht, J.H. Ostrom, G. Viohl, & P. Wellnhofer (eds)|conference=The Beginnings Of Birds| booktitle=proceedings of the International Archaeopteryx Conference, Eichstätt, 1984| location=Eischtatt |publisher=Freunde des Jura-Museums Eichstätt|pages=185-197| id=isbn 3-9801178-0-4}}</ref> and [[Gregory S. Paul]] in 1988.<ref name=paul1988b/>
Studies by [[Phil Senter]] in 2006 indicated that ''Deinonychus'' forelimbs could be used not only for grasping but also for clutching objects towards the chest. The likely presence of large wing feathers in ''Deinonychus'', however, would have limited the range of motion of the forelimbs to some degree. For example, when ''Deinonychus'' extended its arm forward, the 'palm' of the hand automatically rotated to an upward-facing position. This would have caused one wing to block the other if both forelimbs were extended at the same time, leading Senter to conclude that clutching objects to the chest would have only been accomplished with one arm at a time. The function of the fingers would also have been limited by feathers; for example, only the third digit of the hand could have been employed in activities such as probing crevices for small prey items, and only in a position perpendicular to the main wing.<ref>{{cite journal |last=Senter |first=P. |year=2006 |title=Comparison of Forelimb Function Between ''Deinonychus'' And ''Bambiraptor'' (Theropoda: Dromaeosauridae)|journal=Journal of Vertebrate Paleontology |volume=26 |pages=897–906| id=<!--complicated coding necessary because of *$%ing square brackets-->{{doi|id= 10.1671/0272-4634(2006)26%5B897:COFFBD%5D2.0.CO;2| label=10.1671/0272-4634(2006)26[897:COFFBD]2.0.CO;2}} |doi=10.1671/0272-4634(2006)26[897:COFFBD]2.0.CO;2 }}}</ref> [[Alan Gishlick]], in a 2001 study of ''Deinonychus'' forelimb mechanics, found that even if large wing feathers were present, the grasping ability of the hand would not have been significantly hindered; rather, grasping would have been accomplished perpendicular to the wing, and objects likely would have been held by both hands simultaneously in a "bear hug" fashion, finding which have been supported by the later forelimb studies by Carpenter and Senter.<ref name="gishlick2001">{{cite book|title=New Perspectives on the Origin and Early Evolution of Birds |edition= |year=2001 |chapter= The function of the manus and forelimb of ''Deinonychus antirrhopus'' and its importance for the origin of avian flight |editor=Gauthier, J. and Gall, L.F. |author=Gishlick, A.D. |pages=301-318| location=New Haven|publisher=Yale Peabody Museum|isbn= }}</ref>
Parsons has shown that juvenile and sub-adult specimens of ''Deinonychus'' display some morphological differences with the adults. For instance, the arms of the younger specimens were proportionally longer than those of the adults, a possible indication of difference in behavior between young and adults.<ref>{{cite journal |last=Parsons |first=W. |coauthors=Parsons, K. |year=2006 |title=Morphology And Size Of An Adult Specimen Of ''Deinonychus antirrhopus'', (Saurischia, Theropoda) |journal=Journal of Vertebrate Paleontology |volume=26 |issue=3 sup. |pages=109A}}</ref>
===Speed===
Dromaeosaurids, especially ''Deinonychus'', are often depicted as unusually fast-running animals in the popular media, and Ostrom himself speculated that ''Deinonychus'' was fleet-footed in his original description.<ref name="ostrom1969"/> However, when first described, a complete leg of ''Deinonychus'' had not been found, and Ostrom's speculation about the length of the [[femur]] (upper leg bone) later proved to have been an overestimate. In a later study, Ostrom noted that the [[ratio]] of the femur to the [[tibia]] (lower leg bone) is not as important in determining speed as the relative length of the foot and lower leg. In modern, fleet-footed birds like the [[ostrich]], the foot-tibia ratio is .95. In unusually fast-running dinosaurs like ''[[Struthiomimus]]'', the ratio is .68, but in ''Deinonychus'', the ratio is .48. Ostrom stated that the "only reasonable conclusion" is that ''Deinonychus'' was not particularly fast compared to other dinosaurs, and certainly not as fast as modern flightless birds.<ref name="ostrom1976"/>
The low foot to lower leg ratio in ''Deinonychus'' is due partly to an unusually short [[metatarsus]] (upper foot bones). The ratio is actually larger in smaller individuals than in larger ones. Ostrom suggested that the short metatarsus may be related to the function of the sickle claw, and used the fact that it appears to get shorter as individuals aged as support for this. He interpreted all these features – the short second toe with enlarged claw, short metatarsus, etc. – as support for the use of the hind leg as an offensive weapon, where the sickle claw would strike downwards and backwards, and the leg pulled back and down at the same time, slashing and tearing at the prey. Ostrom suggested that the short metatarsus reduced overall stress on the leg bones during such an attack, and interpreted the unusual arrangement of muscle attachments in the ''Deinonychus'' leg as support for his idea that a different set of muscles were used in the predatory stroke than in walking or running. Therefore, Ostrom concluded that the legs of ''Deinonychus'' represented a balance between running adaptations needed for an agile predator, and stress-reducing features to compensate for its unique foot weapon.<ref name="ostrom1976"/>
In his 1981 study of Canadian dinosaur footprints, [[Richard Kool]] produced rough walking speed estimates based on several track-ways made by different species in the [[Gething Formation]] of [[British Columbia]]. Kool estimated one of these track-ways, representing the [[Ichnotaxon|ichnospecies]] ''Irenichnites gracilis'' (which may have been made by ''Deinonychus''), to have a walking speed of 10.1 kilometers per hour (6 miles per hour).<ref name="kool1981">Kool, R. (1981). "The walking speed of dinosaurs from the Peace River Canyon, British Columbia, Canada." ''Canadian Journal of Earth Science'', '''18''': 823-825.</ref>
===Eggs===
The identification in 2000 of a probable ''Deinonychus'' egg associated with one of the original specimens allowed comparison with other theropod dinosaurs in terms of egg structure, nesting, and reproduction. In their 2006 examination of the specimen, Grellet-Tinner and Makovicky examined the possibility that the dromaeosaurid had been feeding on the egg, or that the egg fragments had been associated with the ''Deinonychus'' skeleton by coincidence. They dismissed the idea that the egg had been a meal for the theropod, noting that the fragments were sandwiched between the belly ribs and forelimb bones, making it impossible that they represented contents of the animal's stomach. In addition, the manner in which the egg had been crushed and fragmented indicated that it had been intact at the time of burial, and was broken by the fossilization process. The idea that the egg was randomly associated with the dinosaur were also found to be unlikely; the bones surrounding the egg had not been scattered or disarticulated, but remained fairly intact relative to their positions in life, indicating that the area around and including the egg was not disturbed during preservation. The fact that these bones were belly ribs ([[gastralium|gastralia]]), which are very rarely found articulated, supported this interpretation. All the evidence, according to Grellet-Tinner and Makovicky, indicates that the egg was intact beneath the body of the ''Deinonychus'' when it was buried. It is possible that this represents brooding or nesting behavior in ''Deinonychus'' similar to that seen in the related [[troodontid]]s and [[oviraptorid]]s, or that the egg was in fact inside the [[oviduct]] when the animal died.<ref name="grellet-tinner&makovicky2006"/>
Examination of the ''Deinonychus'' egg's microstructure confirms that it belonged to a theropod, since it shares characteristics with other known theropod eggs and shows dissimilarities with [[ornithischia]]n and [[sauropod]] eggs. Compared to other [[maniraptora]]n theropods, the egg of ''Deinonychus'' is more similar to those of [[oviraptorid]]s than to those of [[troodontid]]s, despite studies which show the latter are more closely related to dromaeosaurids like ''Deinonychus''. While the egg was too badly crushed to accurately determine its size, Grellet-Tinner and Makovicky estimated a diameter of about 7 cm (2.7 in) based on the width of the pelvic canal through which the egg had to have passed. This size is similar to the 7.2 cm diameter of the largest ''[[Citipati]]'' (an oviraptorid) eggs; ''Citipati'' and ''Deinonychus'' also shared the same overall body size, supporting this estimate. Additionally, the thicknesses of ''Citipati'' and ''Deinonychus'' eggshells are almost identical, and since shell thickness correlates with egg volume, this further supports the idea that the eggs of these two animals were about the same size.<ref name="grellet-tinner&makovicky2006"/>
==References==
{{reflist|2}}
==External links==
{{Commons}}
{{Wikispecies|Deinonychus}}
{{portalpar|Dinosaurs}}
{{featured article}}
* [http://palaeos.com/Vertebrates/Units/340Theropoda/340.800.html#Dromaeosauridae Dromaeosauridae at Palaeos.com (technical)]
* [http://www.users.qwest.net/~jstweet1/dromaeosauridae.htm Dromaeosauridae at ''Thescelosaurus'' web site (overview of all Dromaeosaurid genera)]
[[Category:Cretaceous dinosaurs]]
[[Category:Dinosaurs of North America]]
[[Category:Dromaeosaurs]]
[[ar:دينونيتشوس]]
[[ca:Deinonychus]]
[[cs:Deinonychus]]
[[da:Deinonychus]]
[[de:Deinonychus]]
[[es:Deinonychus]]
[[fr:Deinonychus]]
[[it:Deinonychus antirrhopus]]
[[he:דיינוניכוס]]
[[lv:Deinonikss]]
[[hu:Deinonychus]]
[[ms:Deinonychus]]
[[nl:Deinonychus]]
[[ja:デイノニクス]]
[[no:Deinonychus]]
[[pl:Deinonych]]
[[pt:Deinonico]]
[[ru:Дейноних]]
[[simple:Deinonychus]]
[[sk:Deinonychus]]
[[fi:Deinonychus]]
[[sv:Deinonychus]]
[[vi:Deinonychus]]
[[zh:恐爪龙]]