▁et ▁al . ▁think ▁the ▁primary ▁function ▁of ▁the ▁third ▁finger ▁was ▁the ▁attachment ▁of ▁the ▁wing ▁memb rane , ▁or ▁pat ag ium , ▁as ▁their ▁fingers ▁were ▁probably ▁surrounded ▁by ▁memb ran ous ▁t issue ▁and ▁had ▁limited ▁mob ility . ▁ ▁Among ▁sc ans ori opter yg ids , ▁Amb opter y x ▁was ▁most ▁closely - related ▁to ▁Y i , ▁with ▁which ▁it ▁shared ▁a ▁" st yl iform ▁element ", ▁an ▁el ong ate ▁b one ▁that ▁extended ▁from ▁the ▁dist al ▁( far ) ▁end ▁of ▁the ▁ul na . ▁The ▁st yl iform ▁element ▁was ▁slightly ▁cur ved ▁and ▁t aper ed ▁towards ▁the ▁dist al ▁end . ▁It ▁supported ▁the ▁wing ▁memb rane , ▁which ▁stretch ed ▁from ▁the ▁third ▁finger ▁down ▁to ▁the ▁ab d omen . ▁ ▁The ▁for el im bs ▁of ▁Amb opter y x ▁were ▁about ▁ 1 . 3 ▁times ▁longer ▁than ▁the ▁h ind lim bs , ▁with ▁the ▁ul na ▁being ▁shorter ▁than ▁the ▁hum er us ▁and ▁almost ▁twice ▁as ▁wide ▁as ▁the ▁width ▁of ▁the ▁radius . ▁Un like ▁most ▁other ▁non - av ian ▁ther op ods , ▁it ▁had ▁a ▁short ▁tail ▁that ▁lack ed ▁a ▁trans itional ▁point ▁and ▁ended ▁in ▁a ▁pyg ost yle , ▁a ▁set ▁of ▁f used ▁tail ▁verte bra e . ▁The ▁only ▁other ▁non - av ian ▁ther op od ▁that ▁are ▁known ▁to ▁have ▁had ▁a ▁pyg ost yle ▁are ▁certain ▁o vi ra