Galliformes is a large and diverse group comprising about 70 genera and more than 250 species. Taxa within Galliformes are commonly referred to as 'gallinaceous birds' (meaning chicken-like) or game birds (as many species are hunted). There is much ongoing discussion about the number of recognized families within Galliformes. Howard and Moore’s Complete Checklist of the Birds of the World (2003) lists: Megapodiidae (scrub fowl, brush-turkeys, mallee fowl), Cracidae (guans, chachalacas, curassows), Numididae (Guineafowl), Odontophoridae (New World quails) and Phasianidae (grouse, turkeys, pheasants and partridges). Gallinaceous birds are chicken-like in appearance, with small to large bodies and blunt-wings. Plumage coloration ranges from cryptic to dark to brightly colorful. Some gallinaceous birds have elaborate head and neck ornamentation including wattles and casques. Some are primarily arboreal and others are terrestrial. Social groups may range from solitary dwellers to mated pairs to gregarious flocks. Mating systems range from monogamy to polygyny to polygynandry. Megapodes, also known as mound builders, bury their eggs, which are incubated by heat from decaying vegetation, sun-warmed sand, or geothermal sources. Cracids may play an important role in the forest ecosystem as seed predators and dispersers. Some phasianoid galliforms have been domesticated and are kept as ornamentals or are bred and raised for human consumption.