Utente:Mariomassone/Sandbox: differenze tra le versioni

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Nel descrivere ''Deinonychus'', Ostrom lo paragonò con lo [[Struthio camelus|struzzo]] e il [[Casuarius casuarius|casuario]], notando che entrambi questi uccelli sono forniti di artigli letali sul secondo dito.<ref name="ostrom1969"/> Il casuario in particolare è fornito d'un artiglio lungo 125 mm.<ref name=Davies2002>Davies, S.J.J.F. (2002) "Ratites and Tinamous" Oxford University Press. New York, USA</ref> Ostrom citò Gilliard (1958) nel descrivere come il casuario è capace di menomare e sventrare un umano.<ref name=Gilliard1958>Gilliard, E. T. (1958) "Living birds of the world" Doubleday, garden City, NY. USA. 400p.</ref> Degli studi condotti nel 1999 e nel 2003 però mostrarono che fra 241 attacchi da parte di casuari registrati, perirono solo una persona e due cani. Non ci furono prove che le vittime fossero smembrate o sventrate.<ref name=Kofron1999>{{cite journal | last1 = Kofron | first1 = Christopher P. | doi = 10.1111/j.1469-7998.1999.tb01206.x | title = Attacks to humans and domestic animals by the southern cassowary (Casuarius casuarius johnsonii) in Queensland, Australia | journal = Journal of Zoology | year = 1999 | volume = 249 | pages=375–381 | issue = 4 }}</ref><ref name=Kofron2003>{{cite journal | last1 = Kofron | first1 = Christopher P. | year = 2003 | title = Case histories of attacks by the southern cassowary in Queensland | url = | journal = Memoirs of the Queensland Museum | volume = 49 | issue = 1| pages = 335–338 }}</ref> I casuari infatti usano i loro artigli per difendersi, per attaccare minacce, e per minacciare i rivali.<ref name="Davies2002"/> La [[Cariamidae|seriema]] è un altro uccello dotato d'un artiglio ingrandito sul secondo dito; lo usa per smembrare piccole prede prima di consumarle.<ref name=Redford&Peters1986>{{cite journal | last1 = Redford | first1 = Kent H. | last2 = Peters | first2 = Gustav | year = 1986| title = Notes on the biology and song of the red-legged seriema (cariama cristata) | journal = Journal of Field Ornithology | volume = 57 | issue = 4| pages = 261–269 | jstor=4513154}}</ref>

PhillipUno Manningstudio andcondotto colleaguesnel (2009) attemptedper tomettere testalla theprova functionla offunzionalità thedegli sickleartigli clawposteriori ande similarlyanteriori shaped claws on the forelimbs. They analyzed the bio-mechanics of how stresses and strains would be distributed along the claws and into the limbs, using X-ray imaging to create a three-dimensional contour map of a forelimb claw fromdi ''[[Velociraptor]]''. Formostrò comparison,paralleli they analyzed the construction ofstrutturali a clawquelli from a modern predatory bird, thedel [[eagleBubo bubo|gufo owlreale]]. They found that, basedi oncui theartigli waysono thatprincipalmente stressusati wasper conducted along the claw, they were ideal for climbingl'arrampicamento. TheGli scientistsscienziati foundcoinvolti thatnello thestudio sharpenednotarono tipche ofla thepunta clawdel wassecondo a puncturing and gripping instrument, while the curved and expandedartiglio clawposteriore basefosse helpedideale transferper stressperforare loadse evenlyaggrappare.<ref name=manningetal2009>{{cite journal | doi = 10.1002/ar.20986 | last1 = Manning | first1 = P.L. | last2 = Margetts | first2 = L. | last3 = Johnson | first3 = M.R. | last4 = Withers | first4 = P.J. | last5 = Sellers | first5 = W.I. | last6 = Falkingham | first6 = P.L. | last7 = Mummery | first7 = P.M. | last8 = Barrett | first8 = P.M. | last9 = Raymont | first9 = D.R. | year = 2009 | title = Biomechanics of dromaeosaurid dinosaur claws: Application of X-ray microtomography, nanoindentation, and finite element analysis | url = | journal = The Anatomical Record: Advances in Integrative Anatomy and Evolutionary Biology | volume = 292 | issue = 9| pages = 1397–1405 |display-authors=etal}}</ref> Nel paragonare gli artigli dei dromaeosauridi a quelli di certi animali odierni, fu notato che il livello di curvatura negli artigli può essere usato come indizio di stile di vita, con artigli più ricurvi indicando una vita più o meno arboricola. Gli artigli posteriori di ''Deinonychus'' infatti dimostrano una curvatura di 160 gradi, un livello tipico di animali arboricoli. Persino gli artigli anteriori mostravano una curvatura simile.<ref name=manningetal2009/>

The Manning team also compared the curvature of the dromaeosaurid "sickle claw" on the foot with curvature in modern birds and mammals. Previous studies had shown that the amount of curvature in a claw corresponded to what lifestyle the animal has: animals with strongly curved claws of a certain shape tend to be climbers, while straighter claws indicate ground-dwelling lifestyles. The sickle-claws of the dromaeosaurid ''Deinonychus'' have a curvature of 160 degrees, well within the range of climbing animals. The forelimb claws they studied also fell within the climbing range of curvature.<ref name=manningetal2009/>

Paleontologist Peter Mackovicky commented on the Manning team's study, stating that small, primitive dromaeosaurids (such as ''[[Microraptor]]'') were likely to have been tree-climbers, but that climbing did not explain why later, gigantic dromaeosaurids such as ''[[Achillobator]]'' retained highly curved claws when they were too large to have climbed trees. Mackovicky speculated that giant dromaeosaurids may have adapted the claw to be used exclusively for latching on to prey.<ref name=newscientistclaws2009>{{cite journal |authorlink= |date=September 2009 |title=Velociraptor's 'killing' claws were for climbing |journal=New Scientist |volume= |issue=2725 |pages= |url=http://www.newscientist.com/article/mg20327254.100-velociraptors-killing-claws-were-for-climbing.html |accessdate=2009-09-15 }}</ref>