This order contains a group of birds resembling Quails in size and appearance, and to a considerable extent in plumage, but distinguished (so far, at least, as Indian forms are concerned) by wanting the hallux and by having only the three anterior toes. The Hemipodii differ in several important anatomical characters from the Gallinae (see Huxley, P. Z. S. 1868, p. 303). The vertebras are all free, whereas in both Gallinae and Pterocletes the last cervical and anterior dorsals are always anchylosed in adults, and the last dorsal is united with the lumbar vertebra; to form the sacrum. The sternum of Hemipodii has a single deep notch, about two-thirds of the whole length, on each side of the posterior border, and the episternal process is incompletely perforated to receive the inner ends of the coracoids. The palate is schizognathous, but the palatines, pterygoids, and basipterygoids are Pluvialine rather than Galline in form. The nasals are schizorhinal.
As in other three-toed birds, the deep plantar tendons in Turnix unite and the combined tendon is divided to supply the three anterior digits. The ambiens is present, and so are the other muscles of the thigh, except the accessory femoro-caudal, which is wanting. The left carotid only occurs in the genus Turnix. In other characters members of this order resemble the Gallinae. They are quincubital and possess a tufted oil-gland and 14 to 15 cervical vertebras. The young are hatched covered with down, which is marked with a coloured pattern, and they run as soon as they leave the egg.
This order contains two genera or generic groups—Turnix, with three toes, found throughout the warmer parts of the Old "World, including Australia; and Pedionomus, with four toes, peculiar to Australia, and classed by many writers in a distinct family.