ars omet at ars al ▁and ▁ped al ▁ph al anges ▁( to e ▁b ones ). ▁ ▁Un like ▁in ▁some ▁pre histor ic ▁birds , ▁av is aur id ▁t ars omet at ars als ▁were ▁not ▁completely ▁f used , ▁with ▁the ▁dist al ▁( outer ) ▁parts ▁of ▁the ▁met at ars als ▁being ▁separate ▁from ▁each ▁other . ▁The ▁proxim al ▁( near ) ▁half ▁of ▁met at ars al ▁III ▁( the ▁long ▁b one ▁in ▁the ▁middle ▁of ▁the ▁t ars omet at ars us ) ▁is ▁convex ▁from ▁the ▁front . ▁The ▁inside ▁edge ▁of ▁this ▁b one ' s ▁tro ch lea ▁( to e ▁joint ) ▁has ▁a ▁b ony ▁tab ▁which ▁points ▁down ward , ▁known ▁as ▁a ▁plant ar ▁projection . ▁The ▁inn erm ost ▁b one ▁of ▁the ▁t ars omet at ars us , ▁met at ars al ▁I , ▁is ▁small , ▁later ally ▁com pressed ▁( fl atten ed ▁from ▁side - to - side ), ▁and ▁J - sh aped ▁from ▁the ▁side . ▁It ▁is ▁connected ▁to ▁a ▁revers ed ▁hall ux ▁sport ing ▁a ▁very ▁large ▁and ▁cur ved ▁cla w . ▁ ▁Ch ia ppe ▁and ▁Cal vo ▁( 1 9 9 4 ) ▁found ▁that ▁the ▁A vis aur idae ▁shared ▁adapt ations ▁of ▁the ▁foot   — ▁including ▁a ▁fully ▁revers ed ▁and ▁dist ally ▁placed ▁hall ux ▁with ▁a ▁large ▁cla w   — ▁that ▁indicated ▁the ▁ability ▁to ▁per