▁been ▁assumed ▁that ▁the ▁eyes ▁were ▁all ▁comp ound , ▁like ▁ar th rop ods ' ▁later al ▁eyes , ▁but ▁this ▁reconst ruction , ▁which ▁is ▁not ▁back ed ▁up ▁by ▁any ▁evidence , ▁is ▁" some what ▁f anc iful ". ▁The ▁mouth ▁was ▁under ▁the ▁head , ▁behind ▁the ▁prob os cis , ▁and ▁pointed ▁backwards , ▁so ▁that ▁the ▁dig est ive ▁tract ▁formed ▁a ▁U - b end ▁on ▁its ▁way ▁towards ▁the ▁rear ▁of ▁the ▁animal . ▁The ▁prob os cis ▁appeared ▁sufficiently ▁long ▁and ▁flexible ▁to ▁reach ▁the ▁mouth . ▁ ▁The ▁main ▁part ▁of ▁the ▁body ▁was ▁typically ▁about ▁ ▁wide ▁and ▁had ▁ 1 5 ▁segments , ▁on ▁each ▁of ▁which ▁there ▁were ▁pairs ▁of ▁lo bes ▁( f laps ) ▁pointing ▁down wards ▁and ▁out wards . ▁The ▁lo bes ▁over la pped ▁so ▁that ▁the ▁front ▁of ▁each ▁was ▁covered ▁by ▁the ▁rear ▁edge ▁of ▁the ▁one ▁ahead ▁of ▁it . ▁The ▁body ▁ended ▁with ▁what ▁looked ▁like ▁a ▁single ▁con ical ▁segment ▁bearing ▁three ▁pairs ▁of ▁over la pping ▁lo bes ▁that ▁pointed ▁up ▁and ▁out , ▁forming ▁a ▁tail ▁like ▁a ▁V - sh aped ▁double ▁fan . ▁ ▁Inter pret ations ▁of ▁other ▁features ▁of ▁Op ab in ia ▁foss ils ▁differ . ▁Since ▁the ▁animals ▁did ▁not ▁have ▁min eral ized ▁arm or ▁nor ▁even ▁t ough ▁organ ic ▁ex os ke let ons ▁like ▁those ▁of ▁insect s , ▁their ▁bodies ▁were ▁fl atten ed ▁as ▁they