▁pl esi omorphic ▁( un alter ed ) ▁and ▁robust ▁post c ran ial ▁ske let ons . ▁Their ▁five - to ed ▁feet ▁are ▁often ▁hoof ed ▁with ▁the ▁t ars als ▁similar ▁to ▁those ▁of ▁ung ul ates , ▁which ▁feature ▁had ▁led ▁to ▁previously ▁suggested ▁t ies ▁to ▁ar ct ocy on id ▁" cond yl arth s ", ▁but ▁this ▁similarity ▁is ▁now ▁considered ▁primitive . ▁ ▁Classification ▁The ▁p ant od ont s ▁were ▁previously ▁grouped ▁with ▁the ▁ung ul ates ▁as ▁amb ly pod s , ▁pa en ung ul ates , ▁or ▁ar ct ocy on ids , ▁but ▁since ▁ ▁they ▁have ▁been ▁al lied ▁with ▁the ▁till od ont s ▁and ▁considered ▁to ▁be ▁derived ▁from ▁the ▁c im ol est ids . ▁The ▁inter rel ations hip ▁within ▁P ant od ont a ▁is ▁controvers ial , ▁but , ▁following ▁, ▁it ▁contains ▁about ▁two ▁dozen ▁gener a ▁in ▁ten ▁families . ▁Most ▁of ▁the ▁families ▁are ▁known ▁from ▁the ▁Pale oc ene ▁of ▁either ▁Asia ▁or ▁North ▁America . ▁The ▁p ant ol amb d od ont ids ▁and ▁c ory ph od ont ids ▁surv ived ▁into ▁the ▁E oc ene ▁and ▁the ▁latter ▁are ▁known ▁from ▁across ▁the ▁northern ▁hem is phere . ▁Some ▁dent al ▁features ▁can ▁possibly ▁link ▁the ▁most ▁primit ve ▁p ant od ont s ▁to ▁the ▁p ala e ory ct ids , ▁a ▁group ▁of ▁small ▁and ▁insect iv orous ▁m amm als ▁that