n iv orous , ▁and ▁had ▁a ▁c rop ▁for ▁food ▁storage . ▁ ▁They ▁are ▁unlikely ▁to ▁have ▁dw elt ▁in ▁fresh ▁or ▁bra ck ish ▁water . ▁Many ▁am mon ites ▁were ▁likely ▁filter ▁feed ers , ▁so ▁adapt ations ▁associated ▁with ▁this ▁l ifest yle ▁like ▁sie ves ▁probably ▁occurred . ▁ ▁Size ▁ ▁F ew ▁of ▁the ▁am mon ites ▁occurr ing ▁in ▁the ▁lower ▁and ▁middle ▁part ▁of ▁the ▁Jur ass ic ▁period ▁reached ▁a ▁size ▁exceed ing ▁ 2 3   cm ▁( 9   in ) ▁in ▁diameter . ▁Much ▁larger ▁forms ▁are ▁found ▁in ▁the ▁later ▁rocks ▁of ▁the ▁upper ▁part ▁of ▁the ▁Jur ass ic ▁and ▁the ▁lower ▁part ▁of ▁the ▁C ret ace ous , ▁such ▁as ▁T itan ites ▁from ▁the ▁Port land ▁Stone ▁of ▁Jur ass ic ▁of ▁southern ▁England , ▁which ▁is ▁often ▁ 5 3   cm ▁( 2   ft ) ▁in ▁diameter , ▁and ▁Par ap uz os ia ▁se ppen rad ensis ▁of ▁the ▁C ret ace ous ▁period ▁of ▁Germany , ▁which ▁is ▁one ▁of ▁the ▁largest ▁known ▁am mon ites , ▁sometimes ▁reaching ▁ 2   m ▁( 6 . 5   ft ) ▁in ▁diameter . ▁The ▁largest ▁documented ▁North ▁American ▁am mon ite ▁is ▁Par ap uz os ia ▁br ady i ▁from ▁the ▁C ret ace ous , ▁with ▁spec im ens ▁meas uring ▁ 1 3 7   cm ▁( 4 . 5   ft ) ▁in ▁diameter . ▁