. Bulletin. Natural history; Natuurlijke historie. 24 PEABODY MUSEUM BULLETIN 30 of bone almost triradiate in shape. Anteriorly a thin but deep process meets the posterior ramus of the maxilla in a weak overlapping contact. Posteriorly, a thin, tapered, two-pronged process contacted the quadratojugal in what appears to have been a weak tongue-and-groove articulation. Dorsally, a somewhat more ro- bust, grooved process met the postorbital. The latter separated the orbit and lat- eral temporal fenestra. The posterior process marks the ventral limit of the lateral fenestra. The sweeping curve of
. Bulletin. Natural history; Natuurlijke historie. 24 PEABODY MUSEUM BULLETIN 30 of bone almost triradiate in shape. Anteriorly a thin but deep process meets the posterior ramus of the maxilla in a weak overlapping contact. Posteriorly, a thin, tapered, two-pronged process contacted the quadratojugal in what appears to have been a weak tongue-and-groove articulation. Dorsally, a somewhat more ro- bust, grooved process met the postorbital. The latter separated the orbit and lat- eral temporal fenestra. The posterior process marks the ventral limit of the lateral fenestra. The sweeping curve of the upper margin of the jugal indicates an orbit of large, if not unusual, size. The external surface is smooth and gently undulated, and, with the exception of articular surfaces for the adjacent elements mentioned above, is unmarked. The internal surface is similar except for a large and irregular depression at the base of the ascending (postorbital) process. This depression, which is the most prominent scar on this element, marks the articulation area of the ectopterygoid. The most remarkable feature of the jugal is the lack of any recognizable con- tact with the lachrymal. There are clear scars for internal and external overlap- ping of the anterior and posterior process by the maxilla and quadratojugal re- spectively, but there is only the faintest suggestion of contact with a preorbital bar just behind the junction with the maxilla. QUADRATOJ UGAL This element is represented by two complete bones of skull YPM 5210 and an incomplete right quadratojugal from skull YPM 5232. The quadratojugal is a T- shaped bone, with the cross-bar oriented almost vertically (Fig. 11). The latter is. FIG. n. Right quadratojugal (reversed) of Deinonychus antirrhopus, YPM 5210, in medial (A) and lateral (B) views. Abbreviations: ju—articular surface for jugal; qu—articular surface for quadrate. the most robust portion, forming a thick, broad blade that apparently overlapped the lower part
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