• Webster's Revised Unabridged Dictionary
    • a Quadratojugal (Anat) Of or pertaining to the quadrate and jugal bones.
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Century Dictionary and Cyclopedia
    • quadratojugal Connected with or representing elements of the quadrate and of the jugal or malar bone; common to these two bones: as, the quadratojugal arch; the quadratojugal articulation.
    • n quadratojugal A bone of the zygomatic arch of birds, etc., interposed between the quadrate bone behind and the jugal or malar bone before: generally a slender rod forming the hinder piece of the zygoma. By some it is identified with the squamosal of mammals — a determination to which few now assent. See cuts under Gallinæ, girdle-bone, temporomastoid, and Trematosaurus.
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In literature:

The quadratojugal exists only as a small spur and is not in contact with the maxillary.
"Middle American Frogs of the Hyla microcephala Group" by William E. Duellman
The mentomecklians do not ossify until approximately the same time that the quadratojugal appears in the upper jaw.
"Neotropical Hylid Frogs, Genus Smilisca" by William E. Duellman