. ▁ ▁Res p ir atory ▁system ▁▁ ▁Scient ists ▁have ▁re construct ed ▁the ▁resp ir atory ▁system ▁of ▁Maj ung as aur us ▁based ▁on ▁a ▁super b ly ▁preserved ▁series ▁of ▁verte bra e ▁( U A ▁ 8 6 7 8 ) ▁recovered ▁from ▁the ▁Ma e var ano ▁Form ation . ▁Most ▁of ▁these ▁verte bra e ▁and ▁some ▁of ▁the ▁rib s ▁contained ▁cav ities ▁( p neum atic ▁foram ina ) ▁that ▁may ▁have ▁resulted ▁from ▁the ▁in fil tr ation ▁of ▁av ian - style ▁l ungs ▁and ▁air ▁sac s . ▁In ▁birds , ▁the ▁neck ▁verte bra e ▁and ▁rib s ▁are ▁h ollow ed ▁out ▁by ▁the ▁cer v ical ▁air ▁sac , ▁the ▁upper ▁back ▁verte bra e ▁by ▁the ▁lung , ▁and ▁the ▁lower ▁back ▁and ▁sac ral ▁( hip ) ▁verte bra e ▁by ▁the ▁ab dom inal ▁air ▁sac . ▁Similar ▁features ▁in ▁Maj ung as aur us ▁verte bra e ▁imply ▁the ▁presence ▁of ▁these ▁air ▁sac s . ▁These ▁air ▁sac s ▁may ▁have ▁allowed ▁for ▁a ▁basic ▁form ▁of ▁av ian - style ▁' flow - through ▁vent ilation ,' ▁where ▁air ▁flow ▁through ▁the ▁l ungs ▁is ▁one - way , ▁so ▁that ▁o xygen - rich ▁air ▁in h aled ▁from ▁outside ▁the ▁body ▁is ▁never ▁mixed ▁with ▁ex h aled ▁air ▁l aden ▁with ▁carbon ▁dio x ide . ▁This ▁method ▁of ▁resp iration , ▁while ▁complicated , ▁is ▁highly ▁efficient .