▁of ▁water ▁per ▁day . ▁ ▁G row th ▁ ▁A ▁ 1 9 9 9 ▁micro scop ic ▁study ▁of ▁A pat osa urus ▁and ▁Br ont osa urus ▁b ones ▁concluded ▁the ▁animals ▁grew ▁rapidly ▁when ▁young ▁and ▁reached ▁near - ad ult ▁sizes ▁in ▁about ▁ 1 0 year s . ▁In ▁ 2 0 0 8 , ▁a ▁study ▁on ▁the ▁growth ▁rates ▁of ▁sau rop ods ▁was ▁published ▁by ▁Thomas ▁Le h man ▁and ▁Hol ly ▁Wood ward . ▁They ▁said ▁that ▁by ▁using ▁growth ▁lines ▁and ▁length - to - mass ▁r ati os , ▁A pat osa urus ▁would ▁have ▁grown ▁to ▁ 2 5 t ▁( 2 5 ▁long ▁tons ; ▁ 2 8 ▁short ▁tons ) ▁in ▁ 1 5 year s , ▁with ▁growth ▁pe aking ▁at ▁ ▁in ▁a ▁single ▁year . ▁An ▁alternative ▁method , ▁using ▁lim b ▁length ▁and ▁body ▁mass , ▁found ▁A pat osa urus ▁grew ▁ ▁per ▁year , ▁and ▁reached ▁its ▁full ▁mass ▁before ▁it ▁was ▁about ▁ 7 0 year s ▁old . ▁These ▁estimates ▁have ▁been ▁called ▁un re li able ▁because ▁the ▁calculation ▁methods ▁are ▁not ▁sound ; ▁old ▁growth ▁lines ▁would ▁have ▁been ▁ob liter ated ▁by ▁b one ▁rem od elling . ▁One ▁of ▁the ▁first ▁identified ▁growth ▁factors ▁of ▁A pat osa urus ▁was ▁the ▁number ▁of ▁sac ral ▁verte bra e , ▁which ▁increased ▁to ▁five ▁by ▁the ▁time ▁of ▁the ▁creature ' s ▁m atur ity . ▁This