atten ed , ▁disc us - sh aped , ▁stream lined ▁shell s , ▁although ▁some ▁am m ono ids ▁were ▁less ▁effective ▁sw imm ers ▁and ▁were ▁likely ▁to ▁have ▁been ▁slow - sw imming ▁bottom - d well ers . ▁Syn ch ro tr on ▁analysis ▁of ▁an ▁a pty ch op hor an ▁am mon ite ▁revealed ▁remains ▁of ▁is op od ▁and ▁m oll usc ▁lar va e ▁in ▁its ▁bu cc al ▁cav ity , ▁indicating ▁at ▁least ▁this ▁kind ▁of ▁am mon ite ▁fed ▁on ▁pl ank ton . ▁▁ ▁They ▁may ▁have ▁avoided ▁pred ation ▁by ▁squ ir ting ▁in k , ▁much ▁like ▁modern ▁ce phal op ods ; ▁in k ▁is ▁occasionally ▁preserved ▁in ▁foss il ▁spec im ens . ▁ ▁The ▁soft ▁body ▁of ▁the ▁creature ▁occupied ▁the ▁largest ▁segments ▁of ▁the ▁shell ▁at ▁the ▁end ▁of ▁the ▁co il . ▁The ▁smaller ▁earlier ▁segments ▁were ▁w alled ▁off ▁and ▁the ▁animal ▁could ▁maintain ▁its ▁bu oy ancy ▁by ▁filling ▁them ▁with ▁gas . ▁Thus , ▁the ▁smaller ▁sections ▁of ▁the ▁co il ▁would ▁have ▁flo ated ▁above ▁the ▁larger ▁sections . ▁ ▁Many ▁am mon ite ▁shell s ▁have ▁been ▁found ▁with ▁round ▁holes ▁once ▁interpreted ▁as ▁a ▁result ▁of ▁lim p ets ▁att aching ▁themselves ▁to ▁the ▁shell s . ▁However , ▁the ▁tri angular ▁formation ▁of ▁the ▁holes , ▁their ▁size ▁and ▁shape , ▁and ▁their ▁presence ▁on ▁both ▁sides ▁of ▁the ▁shell s , ▁corresponding ▁to ▁the ▁upper ▁and