Dinozorlardaki iki-ayakl\u0131l\u0131k antik ve \u00e7ok daha k\u00fc\u00e7\u00fck proto-dinozorlardan miras kalm\u0131\u015ft\u0131. Scott Persons yazd\u0131\u011f\u0131 makalede, bu evrimle\u015fmeyi kuyruklarla a\u00e7\u0131kl\u0131yor. \u201cProto-dinozorlar\u0131n kuyruklar\u0131 b\u00fcy\u00fckt\u00fc, bacaklar\u0131n\u0131 g\u00fc\u00e7lendiren kaslara sahipti\u201d diyor Persons. \u201cBu kas k\u00fctlesine sahip olmak, erken dinozorlar\u0131n ayakta durmalar\u0131 ve iki ayaklar\u0131n\u0131n \u00fcst\u00fcnde y\u00fcr\u00fcmeleri i\u00e7in gereken g\u00fcc\u00fc sa\u011flad\u0131. Modern kertenkelelerin iki ayak \u00fczerindeki y\u00fckseli\u015finde de benzer bir etki g\u00f6r\u00fcyoruz.\u201d<\/p>\n
Zamanla, proto-dinozorlar daha h\u0131zl\u0131 ve daha uzun mesafeler i\u00e7in ko\u015fmaya ba\u015flad\u0131. K\u00fc\u00e7\u00fck \u00f6n di\u015fler v\u00fccut a\u011f\u0131rl\u0131\u011f\u0131n\u0131n azalmas\u0131na ve dengenin iyile\u015fmesine yard\u0131mc\u0131 olurken, arka ekstremite uzamas\u0131 gibi adaptasyonlar, antik dinozorlar\u0131n daha h\u0131zl\u0131 ko\u015fmas\u0131na izin verdi. Sonunda, baz\u0131 proto-dinozorlar d\u00f6rt ayak \u00fczerinde y\u00fcr\u00fcmekten vazge\u00e7tiler.<\/p>\n
Kanada Ara\u015ft\u0131rma Ba\u015fkanl\u0131\u011f\u0131 taraf\u0131ndan y\u00fcr\u00fct\u00fclen ara\u015ft\u0131rmada paleontologlar Persons ve Phil Currie, erken proto-dinozorlar\u0131n yaln\u0131zca avlar\u0131n\u0131 avlamak i\u00e7in ellerini bo\u015faltmak amac\u0131yla iki-ayak \u00fczerinde durduklar\u0131 \u015feklindeki tezle tart\u0131\u015f\u0131yorlar.<\/p>\n
\u201cBu a\u00e7\u0131klamalar tutars\u0131z,\u201d diyor Persons. \u201cBir s\u00fcr\u00fc antik iki-ayakl\u0131 dinozor otoburdu ve erken et\u00e7il dinozorlar bile k\u00fc\u00e7\u00fck \u00f6n ayaklar geli\u015ftirdiler, avlar\u0131 \u00e7i\u011fnemek i\u00e7in ellerini kullanmak yerine, yemeklerini g\u00fc\u00e7l\u00fc \u00e7eneleriyle ele ge\u00e7irmi\u015flerdi.\u201d<\/p>\n
Ancak, iki-ayakl\u0131l\u0131\u011f\u0131n hayvanlara h\u0131zl\u0131 \u015fekilde yard\u0131mc\u0131 olmas\u0131 i\u00e7in evrimle\u015febilece\u011fi do\u011fruysa, atlar ve \u00e7italar gibi memeliler neden iki-ayakl\u0131 de\u011fildir?<\/p>\n
\u201cGenelde memelilerin b\u00fcy\u00fck kuyruk tabanl\u0131 bacak kaslar\u0131 olmad\u0131\u011f\u0131ndan\u201d diye a\u00e7\u0131kl\u0131yor Persons. \u201cFosil kay\u0131tlar\u0131na bakt\u0131\u011f\u0131m\u0131zda, proto-memeli atalar\u0131m\u0131z\u0131n asl\u0131nda bu kaslar\u0131 ne zaman kaybetti\u011fini izleyebiliriz. Permiyen d\u00f6nemde, 252 milyon y\u0131l geride kalm\u0131\u015f gibi g\u00f6r\u00fcn\u00fcyorlar\u201d diyor.<\/p>\n
O zamanlar memeli soyu kaz\u0131 yapmaya ve yuvalarda ya\u015famaya adapte olmu\u015ftu. Kazmak i\u00e7in, g\u00fc\u00e7l\u00fc \u00f6n ayaklar\u0131 vard\u0131. Arka bacak kaslar\u0131 ve kuyruklar\u0131 muhtemelen bir viraj\u0131n dar s\u0131n\u0131rlar\u0131nda manevra yapmay\u0131 zorla\u015ft\u0131r\u0131rd\u0131.<\/p>\n
\u201cAyr\u0131ca avc\u0131lar\u0131n sizi yakalamas\u0131 i\u00e7in ula\u015fmas\u0131 gereken mesafeyi \u00e7ok daha k\u0131salt\u0131yor\u201d diyor Persons. \u201cModern kaz\u0131c\u0131 kemirgenler \u00f6zellikle k\u0131sa kuyruklu olma e\u011filimindedir; tav\u015fanlar\u0131, porsuklar\u0131 ve k\u00f6stebekleri d\u00fc\u015f\u00fcn\u00fcn.\u201d<\/p>\n
Ara\u015ft\u0131rmac\u0131lar, \u00a0kaz\u0131c\u0131 kemirgenlerin atalar\u0131m\u0131zla ayn\u0131 d\u00f6nemde ya\u015famalar\u0131n\u0131n permiyen d\u00f6neminin sonunda meydana gelen kitlesel yok olu\u015flarda atalar\u0131m\u0131z\u0131n hayatta kalmalar\u0131n\u0131 sa\u011flad\u0131\u011f\u0131 teorisini de \u00f6ne s\u00fcrd\u00fcler. Ancak proto-memeliler oyuklar\u0131ndan kurtuldu\u011funda, gittik\u00e7e h\u0131zl\u0131 ko\u015fucular haline d\u00f6n\u00fc\u015ft\u00fc ve onlar\u0131 iki-ayak \u00fczerinde y\u00fcr\u00fcmekle kar\u015f\u0131 kar\u015f\u0131ya getirecek olan kuyruktan da yoksundular.\u00a0<\/strong><\/p>\n Dergi Referans\u0131:<\/strong> W. Scott Persons, Philip J. Currie. The functional origin of dinosaur bipedalism: Cumulative evidence from bipedally inclined reptiles and disinclined mammals. Journal of Theoretical Biology, 2017; 420: 1 DOI: 10.1016\/j.jtbi.2017.02.032<\/p>\n