wer ▁than ▁twenty ▁good ▁spec im ens ▁have ▁been ▁described ; ▁ 3 ▁spec im ens ▁of ▁Op ab in ia ▁are ▁known ▁from ▁the ▁Gre ater ▁Ph yl lop od ▁bed , ▁where ▁they ▁const itute ▁less ▁than ▁ 0 . 1 % ▁of ▁the ▁community . ▁Op ab in ia ▁was ▁a ▁soft - b od ied ▁animal , ▁aver aging ▁about ▁ 5 . 7   cm ▁in ▁length ▁( ex cluding ▁prob os cis ), ▁and ▁its ▁segment ed ▁body ▁had ▁lo bes ▁along ▁the ▁sides ▁and ▁a ▁fan - sh aped ▁tail . ▁The ▁head ▁shows ▁unusual ▁features : ▁five ▁eyes , ▁a ▁mouth ▁under ▁the ▁head ▁and ▁facing ▁backwards , ▁and ▁a ▁prob os cis ▁that ▁probably ▁passed ▁food ▁to ▁the ▁mouth . ▁Op ab in ia ▁probably ▁lived ▁on ▁the ▁se af loor , ▁using ▁the ▁prob os cis ▁to ▁seek ▁out ▁small , ▁soft ▁food . ▁ ▁When ▁the ▁first ▁thorough ▁exam ination ▁of ▁Op ab in ia ▁in ▁ 1 9 7 5 ▁revealed ▁its ▁unusual ▁features , ▁it ▁was ▁thought ▁to ▁be ▁un related ▁to ▁any ▁known ▁ph yl um , ▁although ▁possibly ▁related ▁to ▁a ▁hypoth et ical ▁ancest or ▁of ▁ar th rop ods ▁and ▁of ▁ann el id ▁w orm s . ▁However ▁other ▁finds , ▁most ▁not ably ▁An om al oc aris , ▁suggested ▁that ▁it ▁belonged ▁to ▁a ▁group ▁of ▁animals ▁that ▁were ▁closely ▁related ▁to ▁the ▁ancest ors ▁of ▁ar th rop ods ▁and ▁of ▁which