any of the gallinaceous (that is, fowl-like or chickenlike) birds. The order includes about 290 species, of which the best-known are the turkeys, chickens, quail, partridge, pheasant and peacock (Phasianidae); guinea fowl (Numididae); and grouse (Tetraonidae). Lesser-known members of the order are the megapodes and the chachalacas, guans, and curassows. Although the hoatzin is here treated with the Galliformes, most taxonomists have assigned the hoatzin to the family Opisthocomidae (order Cuculiformes).
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