1. Forelimbs modified as wings, canines large and prominent, greatest skull length less than 35 mm: Order Chiroptera (Bats).
1'. Forelimbs not modified as wings; if canines large and prominent, then greatest skull length greater than 35 mm: 2
2. Back covered with bony plates; teeth a row of small, similar pegs: Order Cingulata, Family Dasypodidae, Dasypus novemcinctus (Armadillo).
2'. Back not covered with bony plates, teeth not as above: 3
3. No upper incisors or, if present, molars bunodont and skull large; feet protected by at least two hooves per foot: Order Artiodactyla (Even-toed Hoofed mammals)
3'. Upper incisors present; if hooves present, then only one per foot: 4
4. Incisors 1/1: Order Rodentia (Rodents).
4'. Incisors more than 1/1: 5
5. Incisors 2/1 (2nd upper incisor behind first incisor); tail length less than ear length: Order Lagomorpha (Rabbits, hares, pikas).
5'. Incisors more than 2/1; if tail length less than ear length (as in bears), then large prominent canines present: 6
6. Upper and lower incisors procumbent, hooklike, and with secondary cusps (when unworn); eyes minute; snout long and pointed and extending well in front of mouth; total length less than 200 mm: Order Soricomorpha (Shrews).
6'. Upper and lower incisors not as described as above; eyes "normal" size; snout not long and pointed, not extending far in front of mouth; total length more than 200 mm: 7
7. Incisors 5/4; tail long, naked, and scaly; ears large and naked: Order Didelphimorphia, Family Didelphidae, Didelphis virginiana (Opossum).
7'. Incisors fewer than 5/4; tail and ears not as above: 8
8. Canines large and extending well beyond level of other teeth; pentadactyl feet provided with claws: Order Carnivora (Carnivores).
8'. Canines, if present, small and not extending beyond level of other teeth; a single hoof-covered toe on each foot: Order Perissodactyla, Family Equidae, genus Equus (Horses).
Key modified from Findley et al. (1975).
Last Update: 26 Jan 2008