now ▁Cam ar as aur us ). ▁ ▁In ▁ 1 9 0 3 ▁El mer ▁R ig gs ▁published ▁a ▁study ▁that ▁described ▁a ▁well - pres erved ▁ske leton ▁of ▁a ▁di pl od oc id ▁from ▁the ▁Grand ▁River ▁Valley ▁near ▁F ru ita , ▁Colorado , ▁Field ▁Museum ▁of ▁Natural ▁History ▁spec imen ▁P 2 5 1 1 2 . ▁R ig gs ▁thought ▁that ▁the ▁depos its ▁were ▁similar ▁in ▁age ▁to ▁those ▁of ▁the ▁Como ▁Bl uff ▁in ▁Wy oming ▁from ▁which ▁Marsh ▁had ▁described ▁Br ont osa urus . ▁Most ▁of ▁the ▁ske leton ▁was ▁found , ▁and ▁after ▁comparison ▁with ▁both ▁Br ont osa urus ▁and ▁A pat osa urus ▁ajax , ▁R ig gs ▁realized ▁that ▁the ▁hol ot ype ▁of ▁A . ajax ▁was ▁imm ature , ▁and ▁thus ▁the ▁features ▁distingu ishing ▁the ▁gener a ▁were ▁not ▁valid . ▁Since ▁A pat osa urus ▁was ▁the ▁earlier ▁name , ▁Br ont osa urus ▁should ▁be ▁considered ▁a ▁junior ▁syn onym ▁of ▁A pat osa urus . ▁Because ▁of ▁this , ▁R ig gs ▁re comb ined ▁Br ont osa urus ▁exc els us ▁as ▁A pat osa urus ▁exc els us . ▁Based ▁on ▁compar isons ▁with ▁other ▁species ▁proposed ▁to ▁belong ▁to ▁A pat osa urus , ▁R ig gs ▁also ▁determined ▁that ▁the ▁Field ▁Columb ian ▁Museum ▁spec imen ▁was ▁likely ▁most ▁similar ▁to ▁A . ex c els us . ▁ ▁Despite ▁R ig gs ' ▁publication , ▁Henry