Utente:Mariomassone/Sandbox: differenze tra le versioni

Versione delle 09:52, 18 lug 2015

Versione delle 10:04, 18 lug 2015

Riga 84:

Uno studio condotto nel 2009 per mettere alla prova la funzionalità degli artigli posteriori e anteriori di ''Velociraptor'' mostrò paralleli strutturali a quelli del [[Bubo bubo|gufo reale]], i cui artigli sono principalmente usati per l'arrampicamento. Gli scienziati coinvolti nello studio notarono che la punta del secondo artiglio posteriore fosse ideale per perforare e aggrappare.<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/>

PaleontologistIl paleontologo Peter Mackovicky commentedfece oncommento thesu Manningquesto team's studystudio, statingdichiarando thatche small, primitive dromaeosaurids (such as ''[[Microraptor]]'l')artiglio wereavrebbe likelydovuto toavere haveun beenulteriore tree-climbersfunzione, butsiccome thatla climbingforma didricurva notfu explainritenuto whyin later,generi giganticdi dromaeosauridstaglia suchgrossa ascome ''[[Achillobator]]'', retainedche highlyerano curvedtroppo clawsgrandi whenper they were too large to have climbed treesarrampicare. Mackovicky speculatedMacovicky thatinfatti giantsuggerì dromaeosauridsche mayfossero haveusati adaptedper thepermettere clawagli toanimali bedi usedaggrappare exclusivelycontro fori latchingfianchi ondi toprede preygrosse.<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>

InNel 2009, Phil Senter publishedpubblicò auno studystudio onsulle dromaeosauriddita toesdei andpiedi showeddei thatdromaeosauridi, theirdimostrando rangeche ofla motionloro wasflessibilità compatiblefosse withcompatibile thecon excavationlo ofscavamento toughentro insecti nestsnidi d'insetti. SenterSuggerì suggestedche thati smallgeneri dromaeosauridspiù suchpiccoli, ascome ''[[Rahonavis]]'' ande ''[[Buitreraptor]]'', werefossero smallabbastanza enoughdiminutivi toda bepoter partialessere [[insectivore]]sinsettivori, whilementre largerquelli generapiù suchgrandi, ascome ''[[Deinonychus]]'' ande ''[[Neuquenraptor]]'', couldavrebbero haveusato usedgli thisartigli abilityper tocatturare catchprede [[vertebrate]] preyrifugiandosi residingnei innidi insect nests. However, Senter did not test whether the strong curvature of dromaeosaurid claws was also conducive to such activitiesd'insetti.<ref name="Senter2009">{{cite journal|author= Senter, P. | title=Pedal function in deinonychosaurs (Dinosauria: Theropoda): a comparative study | year=2009 | publisher= | url = |doi= | journal =Bulletin of the Gunma Museum of Natural History | pages = 1–14| pmid= | volume=13 | issue=}}</ref>

Nel 2011, Denver Fowler e i suoi colleghi suggerirono un nuovo metodo in cui ''Deinonychus'' e gli altri dromaeosauridi avrebbero catturato le prede.<ref name=Fowler>{{Cita pubblicazione|titolo = The Predatory Ecology of Deinonychus and the Origin of Flapping in Birds | autore =Denver W. Fowler | data = 14 dicembre 2011 | url = http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0028964 | doi = 10.1371/journal.pone.0028964}}</ref> Questo modello, nominato il modello di "Contenimento della Preda da parte dei Rapaci" (''"raptor prey restraint"'' o RPR), propone che ''Deinonychus'' uccidesse le sue prede in un modo simile agli [[Rapace|uccelli rapaci]] [[Accipitridae|accipitridi]]; ''Deinonychus'' avrebbe saltato sopra la preda, trattenendola col suo peso corporeo e aggrappandosi strettamente ad essa con gli artigli ricurvi. Come gli accipitridi, il dromaeosauride avrebbe cominciato a nutrirsi mentre la preda fosse ancora viva, fino a che non moriva dissanguata. Questo modello è basato principalmente sulla morfologia e le proporzioni dei piedi dei dromaeosauridi, che sono paragonabili a quelli dei rapaci. Fowler notò che le gambe e i piedi della maggior parte dei dromaeosauridi sono molto simili a quelli delle [[Aquila|aquile]] e gli [[Accipitrinae|sparvieri]], soprattutto quando viene preso in considerazione il secondo artiglio ingrandito e la manovrabilità delle dita. Il metatarso corto e la forza d'impugnatura delle dita però erano più simili a quelli dei [[Asio otus|gufi]]. Il metodo RPR sarebbe anche consistente con altri aspetti anatomici dei dromaeosauridi grandi, come la morfologia delle mandibole e le braccia. È possibile che le braccia fossero ricoperte da penne lunghe utilizzate, insieme alla coda rigida, per bilanciare il predatore mentre ristringeva la preda. Le sue mandibole, che si ritiene fossero relativamente deboli,<ref name=biteme/> potrebbero essere state utilizzate in un movimento a [[Sega (strumento)|sega]] come fa il moderno varano di Komodo.<ref name=jawforce>{{cite doi|10.1098/rspb.2010.0794}}</ref>

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>

In 2009 Phil Senter published a study on dromaeosaurid toes and showed that their range of motion was compatible with the excavation of tough insect nests. Senter suggested that small dromaeosaurids such as ''[[Rahonavis]]'' and ''[[Buitreraptor]]'' were small enough to be partial [[insectivore]]s, while larger genera such as ''[[Deinonychus]]'' and ''[[Neuquenraptor]]'' could have used this ability to catch [[vertebrate]] prey residing in insect nests. However, Senter did not test whether the strong curvature of dromaeosaurid claws was also conducive to such activities.<ref name="Senter2009">{{cite journal|author= Senter, P. | title=Pedal function in deinonychosaurs (Dinosauria: Theropoda): a comparative study | year=2009 | publisher= | url = |doi= | journal =Bulletin of the Gunma Museum of Natural History | pages = 1–14| pmid= | volume=13 | issue=}}</ref>

In 2011, Denver Fowler and colleagues suggested a new method by which dromaeosaurids may have taken smaller prey. This model, known as the "raptor prey restraint" (RPR) model of predation, proposes that dromaeosaurids killed their prey in a manner very similar to extant [[Accipitridae|accipitrid]] [[birds of prey]]: by leaping onto their quarry, pinning it under their body weight, and gripping it tightly with the large, sickle-shaped claws. Like accipitrids, the dromaeosaurid would then begin to feed on the animal while still alive, until it eventually died from blood loss and organ failure. This proposal is based primarily on comparisons between the morphology and proportions of the feet and legs of dromaeosaurids to several groups of extant birds of prey with known predatory behaviors. Fowler found that the feet and legs of dromaeosaurids most closely resemble those of [[eagle]]s and [[hawk]]s, especially in terms of having an enlarged second claw and a similar range of grasping motion. The short [[Tarsometatarsus|metatarsus]] and foot strength, however, would have been more similar to that of [[owl]]s. The RPR method of predation would be consistent with other aspects of dromaeosaurid anatomy, such as their unusual dentition and arm morphology. The arms, which could exert a lot of force but were likely covered in long feathers, may have been used as flapping stabilizers for balance while atop a struggling prey animal, along with the stiff counterbalancing tail. Dromaeosaurid jaws, thought by Fowler and colleagues to be comparatively weak, would have been useful for eating prey alive but not as useful for quick, forceful dispatch of the prey. These predatory adaptations working together may also have implications for the [[Origin of avian flight|origin of flapping]] in [[paravian]]s.<ref name=fowler2011>{{cite journal | author = Fowler, D.W., Freedman, E.A., Scannella, J.B., Kambic, R.E. | year = 2011 | title = The Predatory Ecology of ''Deinonychus'' and the Origin of Flapping in Birds | url = http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0028964 | journal = PLoS ONE | volume = 6 | issue = 12| page = e28964 | doi = 10.1371/journal.pone.0028964 | pmid=22194962|bibcode = 2011PLoSO...628964F | pmc=3237572| last2 = Freedman | last3 = Scannella | last4 = Kambic }}</ref><ref>{{Cite news| last = Choi| first = Charles| title = Velociraptors' Killer Claws Helped Them Eat Prey Alive| newspaper = LiveScience| date = 14 December 2011| url = http://www.livescience.com/17485-velociraptors-killer-claws.html| archiveurl = | postscript = <!-- Bot inserted parameter. Either remove it; or change its value to "." for the cite to end in a ".", as necessary. -->&#123;&#123;inconsistent citations&#125;&#125;}}</ref>

===Comportamenti sociali===