Key to the Major Orders of Mammals in Texas

The Mammals of Texas - Online Edition

KEY TO THE MAJOR GROUPS (ORDERS) OF MAMMALS IN TEXAS

This key, like those on the pages detailing individual Orders, may be used in the standard manner, or you may advance to the next appropriate section by clicking on the highlighted number or name at the end of a subsection.

1.		Body covered dorsally, and tail completely, by bands of bony plates; snout tapering and lacking teeth anteriorly; eight peglike teeth on each side of upper and lower jaws: Order Xenarthra (armadillos, sloths, and allies). Not as above: 2
2.		Body torpedo-shaped; hind legs absent; front limbs developed into paddles; hairless or nearly so; live in ocean or coastal waters: 3 Not as above: 4
3.		Body ending in a broad, horizontally flattened, rounded fluke; no dorsal fin; muzzle squarish, covered with stout bristles; short bristlelike hairs scattered sparingly over rest of body; nostrils terminal; length 2.5 to 4.5 m: Order Sirenia (manatee and allies). Body ending in horizontal, expanded (not rounded) flukes; blowhole (nostrils) on top of head; most Texas forms with dorsal fin; length 2.5 to 30 m: Order Cetacea (whales, porpoises, and dolphins).
4.		Hand and arm developed into leathery wing: Order Chiroptera (bats). Hand and arm normal, not developed into a wing: 5
5.		Hoofed mammals; two or four toes on each foot: Order Artiodactyla (even-toed ungulates). Toes usually armed with claws, not hoofs: 6
6.		Total of 10 upper incisors; big toe of hind foot without claw; tail prehensile: Order Didelphimorphia (opossums). Total of six or less upper incisors; all toes armed with claws; tail not prehensile: 7
7.		Snout highly flexible and protruding conspicuously beyond mouth; eyes very small or hidden; length of head and body usually less than 150 mm: Order Insectivora (shrews and moles). Snout normal, or if protruding conspicuously then length of head and body much more than 150 mm; eyes normal: 8
8.		Total of two incisors in lower jaw, one on each side: 9 Total of four or more incisors in lower jaw (two or three on each side): 10
9.		Total of two incisors in the upper jaw, one on each side so that incisor formula is 1/1: Order Rodentia (rodents). Total of four incisors in the upper jaw, two on each side, one in front of the other in tandem; incisor formula 2/1: Order Lagomorpha (hares and rabbits).
10.		Marine dwellers, fore and hind limbs developed into flippers; tail normal or vestigial, never developed into flukes: Order Pinnipedia (seals and walruses). Mainly land dwellers, limbs never developed into flippers, but hind feet may have webs between the toes: Order Carnivora (carnivores).