• Webster's Revised Unabridged Dictionary
    • n. pl Pygopodes (Zoöl) A division of swimming birds which includes the grebes, divers, auks, etc., in which the legs are placed far back.
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Century Dictionary and Cyclopedia
    • pygopodes An order of swimming and diving birds, the rump-footed birds, having the legs inserted very far back, and buried in the common integument of the body nearly to the heel. Its limits have varied with different writers, but it is now generally considered to include the loons, grebes, and auks, and to exclude the penguins, which, though pygopodous, are otherwise very different in important respects. It then consists of the families Colymbidæ, Podicipedidæ, and Alcidæ. In consequence of the position of the legs, these birds can hardly walk, and when on land they assume a more or less nearly upright attitude. See cuts under Alca, grebe, and loon.
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Webster's Revised Unabridged Dictionary


In literature:

The seventeenth order of Birds, Pygopodes, is represented in the Argentine Ornis by five species of Grebes.
"Argentine Ornithology, Volume I (of 2)" by P. L. Sclater