▁sp ider ▁and , ▁with ▁its ▁body ▁length ▁of ▁ 1   foot ▁( 3 4   cm ) ▁and ▁leg ▁span ▁of ▁above ▁ 2 0   in ches ▁( 5 0   cm ), ▁the ▁largest ▁known ▁sp ider ▁ever ▁to ▁have ▁lived ▁on ▁Earth , ▁but ▁subsequent ▁exam ination ▁by ▁an ▁expert ▁revealed ▁that ▁it ▁was ▁actually ▁a ▁relatively ▁small ▁sea ▁sc orp ion . ▁ ▁By ▁the ▁Jur ass ic , ▁the ▁s oph istic ated ▁aer ial ▁web s ▁of ▁the ▁orb - we aver ▁sp iders ▁had ▁already ▁developed ▁to ▁take ▁advantage ▁of ▁the ▁rapidly ▁divers ifying ▁groups ▁of ▁insect s . ▁A ▁sp ider ▁web ▁preserved ▁in ▁am ber , ▁thought ▁to ▁be ▁ 1 1 0 ▁million ▁years ▁old , ▁shows ▁evidence ▁of ▁a ▁perfect ▁" orb " ▁web , ▁the ▁most ▁famous , ▁circular ▁kind ▁one ▁thinks ▁of ▁when ▁imag ining ▁sp ider ▁web s . ▁An ▁exam ination ▁of ▁the ▁dr ift ▁of ▁those ▁gen es ▁thought ▁to ▁be ▁used ▁to ▁produce ▁the ▁web - sp in ning ▁behavior ▁suggests ▁that ▁orb ▁spin ning ▁was ▁in ▁an ▁advanced ▁state ▁as ▁many ▁as ▁ 1 3 6 ▁million ▁years ▁ago . ▁One ▁of ▁these , ▁the ▁ar ane id ▁Mong olar ach ne ▁jur ass ica , ▁from ▁about ▁, ▁recorded ▁from ▁Da oh u ogo , ▁Inner ▁Mong olia ▁in ▁China , ▁is ▁the ▁largest ▁known ▁foss il ▁of ▁a ▁sp ider . ▁ ▁The ▁ 1 1 0 - mill ion -