A camel's hoof is not really a hoof at all
A hoof is a toe tip armoured in thick keratin, worn by horses, cattle, deer and even some dinosaurs. Camels only look the part: their feet end in soft toes with nails. Real hooves never stop growing, which is why wild animals wear them down and working horses need shoes.
Hooves belong to ungulates, split into two main groups named from Greek words for even and uneven toes. Artiodactyls, the even-toed kind, include giraffes, deer, bison, cattle, goats, pigs and sheep, with two-toed ruminants the most numerous. Perissodactyls, the odd-toed kind, include horses, rhinoceroses and tapirs. Hooves are mostly a placental mammal feature, but the duck-billed dinosaur Edmontosaurus had hoofed hind feet and the marsupial Chaeropus had them too.
Structurally, the hoof encloses the last bone of the toe and the navicular bone. It includes the wall, the bars, the sole, the frog and cushioning soft tissue, with the animal's weight carried by the sole and the rim of the wall. The wall itself has four layers, the middle one forming most of its bulk, and inside lies a laminar junction that binds wall to bone and copes with the enormous forces passing through. A hoof supports weight, absorbs impact, protects inner tissues and provides grip. A healthy one has a thick wall, a deep enough sole, a solid heel and evenly spaced growth rings, with genetics, diet, environment and athletic demands all affecting its condition.
Most even-toed animals walk on a cloven hoof of two main claws, and many also carry two small dewclaws higher up. In deer and pigs these can touch soft ground or help when running and jumping, while mountain goats use them for grip and braking on steep rock, ice or snow. Giraffes and pronghorns have none. Among odd-toed animals, horses and their relatives have a single hoof per foot, while the tapir has three toes on each hind foot and four on each front one.
Because hooves grow constantly, wild animals keep them balanced through wear. Domestic stock may need trimming, as in dairy herds, while horses and working oxen pounding hard roads under heavy loads wear them too fast and are fitted with shoes.
Source: Hoof
