1. Upper incisors present; body shape piglike; elongate canines: Pecari tajacu.
1'. No upper incisors; body shape not piglike; canines absent, or if present, not elongate: 2
2. Males with antlers (females without antlers or horns); a large antorbital fenestra; lateral digits present: Cervidae, 6
2'. Males and females with horns (a bony frontal core covered with a keratinized sheath); large antorbital fenestra absent, or if present, lateral digits lacking or vestigial: 3
3. Horns forked; antorbital fenestra present; lateral digits absent or vestigial: Antilocapra americana.
3'. Horns not forked; antorbital fenestra absent; four hooves (including two vestigial hooves) on each foot: 4
4. Horns smooth and directed laterally and dorsally, slanting somewhat posteriorly; cow-sized; dark brown in color: Bos bison.
4'. Horns with annular ridges, posteriorly curved; sheep-sized: 5
5. Males with midventral mane of hair on neck: Ammotragus lervia.
5'. Males without midventral mane on neck: Ovis canadensis.
6. Antlers with a prominent brow tine; upper canines present; vomer not attached to medial suture of palatines, not separating posterior narial cavity; prominent yellow rump patch: Cervus canadensis.
6'. Antlers without prominent brow tine; upper canines absent; vomer attached to medial suture of palatines, completely separating narial cavity; no large yellow rump patch: 7
7. Tail white, tipped with black tuft; antlers branched dichotomously, anterior and posterior beams nearly equal: Odocoileus hemionus.
7'. Tail white below, brown above; antlers with one main anteriorly directed beam with smaller tines branching dorsally from it: Odocoileus virginianus.
Key slightly modified from Findley (1987).
Last Update: 20 Jul 2005