The class Mammalia consists of 29 orders, 153 families, about 1,200 genera and more than 5,000 species. They are distributed on every continent. They range in size from the 3 centimeter (1.2 in) Kitti's Hog-nosed Bat Craseonycteris thonglongyai to the 33 meter (110 ft) Blue Whale Balaenoptera musculus. About 442 species can be found in North America north of Mexico.