▁the ▁sides . ▁Bud d ▁thought ▁the ▁" tri angles " ▁were ▁too ▁wide ▁to ▁fit ▁within ▁Op ab ini as ▁sl ender ▁body , ▁and ▁that ▁cross - section ▁views ▁showed ▁they ▁were ▁attached ▁separately ▁from ▁and ▁lower ▁than ▁the ▁lo bes , ▁and ▁extended ▁below ▁the ▁body . ▁He ▁later ▁found ▁spec im ens ▁that ▁appeared ▁to ▁preserve ▁the ▁legs ' ▁exterior ▁cut icle . ▁He ▁therefore ▁interpreted ▁the ▁" tri angles " ▁as ▁short , ▁f les hy , ▁con ical ▁legs . ▁He ▁also ▁found ▁small ▁min eral ized ▁patch es ▁at ▁the ▁tips ▁of ▁some , ▁and ▁interpreted ▁these ▁as ▁cla ws . ▁Z hang ▁and ▁Brig gs ▁( 2 0 0 7 ) ▁analyz ed ▁the ▁chemical ▁composition ▁of ▁the ▁" tri angles ", ▁and ▁concluded ▁that ▁they ▁had ▁the ▁same ▁composition ▁as ▁the ▁gut , ▁and ▁therefore ▁agreed ▁with ▁Wh itt ington ▁that ▁they ▁were ▁part ▁of ▁the ▁dig est ive ▁system . ▁Instead ▁they ▁regarded ▁Op ab ini as ▁lo be + g ill ▁arrangement ▁as ▁an ▁early ▁form ▁of ▁the ▁bir am ous ▁lim bs ▁seen ▁in ▁tr il ob ites ▁and ▁cr ust ace ans ▁and ▁which ▁may ▁be ▁the ▁original ▁form ▁in ▁all ▁ar th rop ods . ▁However , ▁this ▁similar ▁chemical ▁composition ▁is ▁not ▁only ▁associated ▁with ▁the ▁dig est ive ▁tract ; ▁Bud d ▁and ▁D ale y ▁suggest ▁that ▁it ▁represents ▁min eral ization ▁forming ▁within ▁fluid - filled ▁cav ities ▁within ▁the ▁body ▁( cons istent ▁with