The Time Before History, Colin Tudge, Simon and Schuster, 1997, ISBN 978-0-684-83052-0, ... Three main groups of ungulates prevail today: the perissodactyls, which carry their weight on their middle toes like horses, rhinos, and tapirs; the artiodactyls - including the pigs, hippos, camels, and ruminants - which bear their weight equally on their third and fourth toes (and hence are "cloven-hoofed"); and the proboscideans, represented by the elephants ...
Horse Power, Jane Buxton, Learning Media Ltd, 2002, ISBN 978-0-478-24718-3, ... Horses' hooves are like your fingernails. They keep growing all the time, and they have to be cut before they get too long. This doesn't hurt a horse at all, just like it doesn't hurt when you cut your fingernails ...
