▁ 1 8 7 7 , ▁and ▁a ▁second ▁species , ▁A . ▁l ou is ae , ▁was ▁discovered ▁and ▁named ▁by ▁William ▁H . ▁Holland ▁in ▁ 1 9 1 6 . ▁A pat osa urus ▁lived ▁about ▁ 1 5 2 ▁to ▁ 1 5 1 ▁million ▁years ▁ago ▁( my a ), ▁during ▁the ▁late ▁Kim mer id g ian ▁to ▁early ▁T ith onian ▁age , ▁and ▁are ▁now ▁known ▁from ▁foss ils ▁in ▁the ▁Mor r ison ▁Form ation ▁of ▁modern - day ▁Colorado , ▁Oklahoma , ▁New ▁Mexico , ▁Wy oming , ▁and ▁Ut ah ▁in ▁the ▁United ▁States . ▁A pat osa urus ▁had ▁an ▁average ▁length ▁of ▁, ▁and ▁an ▁average ▁mass ▁of ▁. ▁A ▁few ▁spec im ens ▁indicate ▁a ▁maximum ▁length ▁of ▁ 1 1 – 3 0 % ▁greater ▁than ▁average ▁and ▁a ▁mass ▁of ▁. ▁ ▁The ▁cer v ical ▁verte bra e ▁of ▁A pat osa urus ▁are ▁less ▁el ong ated ▁and ▁more ▁heavily ▁constructed ▁than ▁those ▁of ▁Di pl od ocus , ▁a ▁di pl od oc id ▁like ▁A pat osa urus , ▁and ▁the ▁b ones ▁of ▁the ▁leg ▁are ▁much ▁stock ier ▁despite ▁being ▁longer , ▁imp lying ▁that ▁A pat osa urus ▁was ▁a ▁more ▁robust ▁animal . ▁The ▁tail ▁was ▁held ▁above ▁the ▁ground ▁during ▁normal ▁lo com otion . ▁A pat osa urus ▁had ▁a ▁single ▁cla w ▁on ▁each ▁for el imb ▁and ▁three ▁on ▁each ▁h ind lim b