▁a ▁dia ph rag m , ▁the ▁dead - space ▁volume ▁( the ▁amount ▁of ▁un used ▁air ▁remaining ▁in ▁the ▁mouth , ▁tra che a , ▁and ▁air ▁tub es ▁after ▁each ▁breath ) ▁has ▁been ▁estimated ▁at ▁about ▁ ▁for ▁a ▁ ▁spec imen . ▁Pal ad ino ▁calcul ates ▁its ▁tid al ▁volume ▁( the ▁amount ▁of ▁air ▁moved ▁in ▁or ▁out ▁during ▁a ▁single ▁breath ) ▁at ▁ ▁with ▁an ▁av ian ▁resp ir atory ▁system , ▁ ▁if ▁m amm al ian , ▁and ▁ ▁if ▁re pt ilian . ▁ ▁On ▁this ▁basis , ▁its ▁resp ir atory ▁system ▁would ▁likely ▁have ▁been ▁par ab ron chi , ▁with ▁multiple ▁pul mon ary ▁air ▁sac s ▁as ▁in ▁av ian ▁l ungs , ▁and ▁a ▁flow - through ▁lung . ▁An ▁av ian ▁resp ir atory ▁system ▁would ▁need ▁a ▁lung ▁volume ▁of ▁about ▁ ▁compared ▁with ▁a ▁m amm al ian ▁requirement ▁of ▁, ▁which ▁would ▁exceed ▁the ▁space ▁available . ▁The ▁overall ▁thor ac ic ▁volume ▁of ▁A pat osa urus ▁has ▁been ▁estimated ▁at ▁, ▁allowing ▁for ▁a ▁, ▁four - ch am ber ed ▁heart ▁and ▁a ▁ ▁lung ▁capacity . ▁That ▁would ▁allow ▁about ▁ ▁for ▁the ▁necessary ▁t issue . ▁Ev idence ▁for ▁the ▁av ian ▁system ▁in ▁A pat osa urus ▁and ▁other ▁sau rop ods ▁is ▁also ▁present ▁in ▁the ▁p neum atic ity ▁of ▁the ▁verte bra e . ▁Though ▁this ▁plays ▁a ▁role ▁in ▁reducing ▁the ▁weight