pid idae ▁is ▁a ▁family ▁of ▁ext inct ▁am phi asp id id ▁heter ost rac an ▁ag n ath ans ▁whose ▁foss ils ▁are ▁restricted ▁to ▁Lower ▁Dev onian ▁marine ▁str ata ▁of ▁Si ber ia ▁near ▁the ▁Ta im yr ▁Pen ins ula . ▁ ▁In ▁life , ▁all ▁am phi asp id ids ▁are ▁thought ▁to ▁be ▁b enth ic ▁animals ▁that ▁lived ▁most ▁of ▁their ▁lives ▁mostly ▁buried ▁in ▁the ▁sed iment ▁of ▁a ▁series ▁of ▁hyp ers al ine ▁l ago ons . ▁Am phi asp ids ▁are ▁easily ▁distinguished ▁from ▁other ▁heter ost rac ans ▁in ▁that ▁all ▁of ▁the ▁pl ates ▁of ▁the ▁ce phal oth or ac ic ▁arm or ▁are ▁f used ▁into ▁a ▁single , ▁m uff - like ▁unit , ▁so ▁that ▁the ▁for eb ody ▁of ▁the ▁living ▁animal ▁would ▁have ▁looked , ▁in ▁the ▁case ▁of ▁ol b ias pid ids , ▁v agu ely ▁like ▁a ▁hot ▁water ▁bott le ▁with ▁a ▁pair ▁of ▁small , ▁or ▁deg ener ated ▁eyes , ▁with ▁each ▁fl ank ed ▁by ▁a ▁pre orb ital ▁opening , ▁and ▁a ▁simple , ▁sl it - like ▁mouth ▁position ed ▁at ▁the ▁an ter i orm ost ▁portion ▁of ▁the ▁ce phal oth or ac ic ▁arm or . ▁ ▁Ol b ias pid ids ▁differ ▁from ▁the ▁am phi asp ido id ▁am phi asp ids ▁of ▁Am phi asp id idae ▁in ▁that ▁ol b ias pid ids ▁have ▁wing - like