The foot structure of piciform and coraciiform birds is examined in detail. Certain similarity in foot structure between woodpeckers and woodhoopoes is shown and provides the basis for the model of the evolutionary formation of the zygodactyl foot. It is shown that African mousebirds and the Madagascan Leptosomus discolor are probably the closest relatives of piciforms. A brief review of fossil groups presumably belonging to the piciform stem is provided.
Paleontological Journal. 2007. V. 41 (3): 290-297.