▁lived ▁from ▁the ▁Car bon ifer ous ▁period ▁( T our na is ian ▁age ) ▁to ▁the ▁Perm ian ▁period ▁( Le on ard ▁age ) ▁( 3 4 5 . 3 ▁to ▁ 2 6 8 . 0 ▁Ma ), ▁when ▁this ▁genus ▁became ▁ext inct . ▁ ▁Description ▁ ▁Arch im edes ▁is ▁a ▁genus ▁of ▁fen est rate ▁b ry oz o ans ▁with ▁a ▁calc ified ▁ske leton ▁of ▁a ▁del icate ▁spir al - sh aped ▁mesh ▁that ▁was ▁thick ened ▁near ▁the ▁axis ▁into ▁a ▁massive ▁c ork s cre w - sh aped ▁central ▁structure . ▁The ▁most ▁common ▁remains ▁are ▁fragments ▁of ▁the ▁mesh ▁that ▁are ▁det ached ▁from ▁the ▁central ▁structure , ▁and ▁these ▁may ▁not ▁be ▁identified ▁other ▁than ▁by ▁association ▁with ▁the ▁" c ork s cre ws ", ▁that ▁are ▁fairly ▁common . ▁Spec im ens ▁in ▁which ▁the ▁mesh ▁remains ▁attached ▁to ▁the ▁central ▁structure ▁are ▁rare . ▁Like ▁other ▁b ry oz o ans , ▁Arch im edes ▁forms ▁colon ies , ▁and ▁like ▁other ▁fen estr ates , ▁the ▁individuals ▁( or ▁zo oid s ) ▁lived ▁on ▁one ▁side ▁of ▁the ▁mesh , ▁and ▁can ▁be ▁recognized ▁for ▁the ▁two ▁rows ▁of ▁equally ▁dist anced ▁rim med ▁por es . ▁Inside ▁the ▁branches , ▁neighbour ing ▁individuals ▁were ▁in ▁contact ▁through ▁small ▁can als . ▁Bry oz o ans ▁are ▁station ary ▁ep ifa unal ▁susp ension ▁feed ers . ▁ ▁Distribution ▁The ▁majority ▁of ▁foss