▁large ▁g land ▁apparently ▁over lies ▁the ▁posterior ▁portion ▁of ▁the ▁gut . ▁A ▁pair ▁of ▁structures ▁on ▁either ▁side ▁of ▁the ▁int est ine ▁and ▁a ▁little ▁behind ▁the ▁st om ach ▁may ▁have ▁been ▁g on ads ▁or ▁dig est ive ▁org ans . ▁Mus cular ▁t issue ▁is ▁apparently ▁preserved ▁in ▁the ▁head ▁and ▁the ▁foot , ▁with ▁a ▁distribution ▁that ▁strik ingly ▁res emb les ▁that ▁observed ▁in ▁modern ▁ch it ons . ▁ ▁The ▁foss ils ▁showed ▁signs ▁of ▁a ▁thick ened ▁central ▁structure ▁that ▁Car on , ▁Sch el tem a ▁et ▁al . ▁( 2 0 0 6 ) ▁thought ▁was ▁on ▁the ▁unders ide ▁and ▁probably ▁represents ▁a ▁mus cular ▁sole ▁that ▁was ▁a ▁little ▁over ▁half ▁as ▁wide ▁as ▁the ▁whole ▁animal . ▁It ▁was ▁U - sh aped , ▁with ▁the ▁" open " ▁end ▁behind ▁the ▁mouth ▁and ▁the ▁rounded ▁end ▁a ▁little ▁forward ▁of ▁the ▁animal ' s ▁rear ▁edge . ▁The ▁an us ▁apparently ▁was ▁slightly ▁ahead ▁of ▁the ▁rounded ▁end . ▁All ▁the ▁edges ▁of ▁the ▁" foot " ▁except ▁the ▁front ▁were ▁surrounded ▁by ▁dark er ▁patch es , ▁which ▁are ▁sometimes ▁separated ▁from ▁the ▁rest ▁of ▁the ▁body ▁by ▁a ▁thin ▁layer ▁of ▁sed iment . ▁ ▁Ph y log eny ▁ ▁Od ont og ri ph us ▁has ▁become ▁prominent ▁in ▁the ▁debate ▁that ▁has ▁gone ▁on ▁since ▁ 1 9 9 0 ▁about ▁the ▁evolution ary ▁orig ins ▁of ▁m oll us cs , ▁ann