Key to the Skulls of North Dakota Mammals

1. Lacrimals articulating with nasals (Fig. 52).......................Bovidae...2
   Lacrimals not articulating with nasals (Fig. 53).............................3

2. Greatest length of skull more than 350mm; length of
     maxillary tooth row more than 120mm; horns projecting
     laterally from skull.............................................Bison bison
                                                                            Bison
   Greatest length of skull less than 350mm; length of
     maxillary tooth row more than 120mm; horns projecting
     posteriorly, sometimes curling...............................Ovis canadenis
                                                                   Mountain Sheep
3. Permanent horn with sheath having one flattened prong (in
     males only) and a recurved tip; sheaths shed annually; foramen
     in frontal bone located medial to base of horn-
     core (Fig. 54).........................Antilocapridae, Antilocapra americana
                                                                        Pronghorn
   Deciduous antlers if present, only in males; foramen in frontal
     located anterior to base of antler (Fig. 55)....................Cervidae...4

4. Nasals shortened and rostrum elongated so that distance from
     front of nasals to front of skull is about equal to the distance
     from back of nasals to back of skull.............................Alces alces
                                                                            Moose
   Nasals not as above..........................................................5


5. One upper canine on each side...................................Cervus elaphus
                                                                    Wapiti or Elk
   Upper canines absent.........................................................6

6. Shallow depression in lacrimal, less than 10mm deep; antlers
     branch from main beam (Fig. 56)........................Odocoileus viginianus
                                                                White-tailed Deer
   Lacrimal fossa a deep pit, more than 10mm deep;
     antlers dichotomously branching..........................Odocoileus hemionus
                                                                        Mule Deer