America’s “antelope” is really a giraffe’s distant cousin
The pronghorn (Antilocapra americana) is a western and central North American artiodactyl nicknamed American antelope though it is not one. Its closest living relatives are the giraffe and okapi. It is the fastest land mammal in the Americas, clocked up to about 55 mph (88.5 km/h).
The pronghorn, Antilocapra americana, is an even-toed hoofed mammal native to the interior west and centre of North America. Locals call it the American antelope, prong buck or prairie antelope, because parallel evolution has made it look and live much like Old World antelopes, but it is not one. It is the sole survivor of the family Antilocapridae, and its closest kin today are the okapi and giraffe; through the infraorder Pecora it is more distantly related to deer, bovids and musk deer. During the Pleistocene, about 11 other antilocaprid species roamed North America, many with long or wildly twisted horns, and three genera, Capromeryx, Stockoceros and Tetrameryx, were still around when humans arrived.
Spanish explorers saw pronghorns in the 16th century, but the species was first properly documented on the Lewis and Clark expedition of 1804 to 1806, where the Niobrara River empties out, in what is now Nebraska. William Clark described shooting a buck and judged it more like an African antelope or gazelle than any goat. The ornithologist George Ord gave the formal description in 1815.
White fur marks the rump, sides, belly, chest and throat. Males measure 1.3 to 1.5 metres long, stand 82 to 104 cm at the shoulder and weigh 40 to 65 kg; females are as tall but lighter, at 34 to 48 kg. Each foot has two hooves and no dewclaws. Huge, high-set eyes give a 320-degree field of view, and unlike deer, pronghorns have a gallbladder.
The name comes from the forward-pointing tine on each branched horn sheath. The horn is a flattened blade of bone covered, as in giraffes, by skin, but here that skin forms a keratin sheath that is shed and regrown every year, something no member of the ox family does. Male sheaths average about 25 cm; female horns are small, straight and seldom pronged. Its top speed of 88.5 km/h beats every other runner in the New World, and the American Society of Mammalogists uses it as an emblem.
Source: Pronghorn
