▁ ▁When ▁the ▁Si oux ▁lived ▁around ▁the ▁Great ▁L akes , ▁they ▁imag ined ▁their ▁myth ical ▁Water ▁Mon ster ▁Un kte hi ▁as ▁a ▁large ▁aqu atic ▁buff alo - like ▁m amm al . ▁This ▁image ▁was ▁likely ▁derived ▁from ▁early ▁observations ▁of ▁large ▁Ple ist oc ene ▁m amm al ▁foss ils ▁like ▁m amm oth s ▁and ▁m ast od ons ▁er oding ▁out ▁of ▁the ▁banks ▁of ▁local ▁la kes ▁and ▁rivers . ▁As ▁some ▁groups ▁of ▁Si oux ▁began ▁moving ▁west ▁into ▁the ▁regions ▁that ▁includes ▁North ▁Dak ota ▁their ▁dep ict ions ▁of ▁Un kte hi ▁t ended ▁to ▁conver ge ▁on ▁the ▁characteristics ▁of ▁local ▁foss ils . ▁Although ▁Un kte hi ▁continued ▁to ▁be ▁described ▁as ▁horn ed , ▁it ▁gradually ▁became ▁imag ined ▁as ▁re pt ilian ▁rather ▁than ▁the ▁m amm al ian ▁port ray als ▁of ▁the ▁Si oux ▁in ▁the ▁Great ▁L akes ▁region , ▁like ▁the ▁din osa urs ▁and ▁mos asa urs ▁of ▁the ▁region ' s ▁Mes oz o ic ▁rock . ▁Un kte hi ▁was ▁described ▁as ▁a ▁sn ak eli ke ▁mon ster ▁equ ipped ▁with ▁feet , ▁like ▁the ▁el ong ate ▁sin uous ▁mos asa urs ▁who ▁had ▁four ▁short ▁lim bs . ▁Its ▁back ▁was ▁described ▁as ▁rid ged ▁and ▁saw ▁like , ▁a ▁configuration ▁similar ▁to ▁the ▁appearance ▁of ▁a ▁foss il ▁verte br al ▁column ▁er oding ▁from ▁rock . ▁In ▁more ▁recent ▁times ▁Lak ota ▁story t eller