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312 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY 20 years ago by the Polish- and Soviet-Mongolian expeditions, but the first review of their osteology was published only recently (Barsbold et al., 1990), and most of the long-known Mongolian cranial specimens still need to be thoroughly studied. New finds of oviraptorids, including an embryonic skeleton, have been reported from Mongolia (Norell et al., 1994; Dashzeveg et al., 1995). The following description is based on the skull of Oviraptor sp. (ZPAL MgD-I/95) in the collection of the Institute of Paleobiology, Polish Academy of Sciences, Warsaw, Poland. This specimen has been illustrated and interpreted in the context of broad, primarily functional, comparisons (Osmolska, 1976) but was never described in detail. Osmolska's (1976) reconstruction of the oviraptorid palate proved correct except for details of the median pterygoid contact. Barsbold (1983a, fig. 12) published an illustration of the similar palate of Oviraptor philoceratops, which is not accompanied by a description and contains a misinterpretation of the vomer as the rostral part of the pterygoid. Both the premaxilla and maxilla bear sharp tomial edges that suggest a cutting function of the jaws (Figure 1). The palatal shelves of the premaxillae and maxillae form an entirely closed "secondary" palate. The two shelves of each bone remain separated by a median suture. Dorsal to the shelves, the body of the premaxilla encloses a spacious sinus. The ventral (palatal) surface of the premaxillary shelves is overlapped by the maxillary shelves. Each maxillary shelf is made of two longitudinal bulges separated by a shallow groove. The shelf is separated from the tomial edge by a deep, probably neurovascular, groove that empties into an opening at the suture with the premaxilla. The tomial edge is continuous with the lateral wall of the bone, which overlaps the premaxilla rostrally. The medial wall is seen in part as a perpendicular stmt, visible in the antorbital fenestra (Figure 2 A), that rises in the midlength of the bone and leaves a large maxillary foramen in front. The medial and lateral walls are both fenestrated and enclose a spacious maxillary sinus (a part of the antorbital fossa) that extends all the way to the caudal (jugal) end of the bone (Figure 2A). The maxilla of Oviraptorphiloceratops has a similar structure (Barsbold et al., 1990, fig. 10.1 A). The maxilla is forked caudally (Figure 1). Each palatal shelf has a prominent knob- or tooth-like caudomedial process. The two caudomedial processes brace the vomer. Caudolaterally, the maxilla continues as a palato-jugal wing that articulates with the palatine, jugal, ectopterygoid, and lacrimal. The vomer is tightly held between the maxilla and the pterygoid. The rostral end of the vomer is strongly expanded and composed of a median knob and lateral wings. The knob is braced and the wings are overlapped by the caudomedial processes of the maxilla. The convoluted suture to the pterygoid suggests a deep interdigitation. The palatine is composed of the maxillary process, which is its only prominent rostral process, and the pterygoid (caudal) qj pm mp plm 1 v fp A^—p 1 c W-ec FIGURE 1.—Reconstruction of the oviraptorid bony palate based on the specimen ZPAL MgD-I/95. Arrow points to the palatine's ascending wing (invisible in this view, see Figure 2). Scale bar=10 mm. (ec=ectopterygoid, fp=postpalatine fenestra, in=intemal naris, ip=interpterygoid vacuity, j=jugal, l=lacrimal, m=maxilla, mp=tooth-like caudomedial process of maxilla, plc=choanal conch (pterygoid wing) of palatine, plm=maxillary process of palatine, pm=premaxilla, pt=pterygoid, ptb=basal wing of pterygoid, q=quadrate, qj=quadratojugal, t=tomial edges of premaxilla and maxilla, v= vomer.) wing, which encloses the choana caudally. The maxillary process has a triangular ascending wing that forms the lateral wall of the choana and articulates with the lacrimal dorsally and the maxilla rostrally (Figure 2B). The pterygoid wing, which is paper-thin and poorly preserved, is strongly convex-concave dor-

B FIGURE 2.—Oviraptorid specimen ZPAL MgD-I/95: A, upper jaw in lateral view; B, lateral wall of the choana in medial view, with a schematic reconstruction of the pterygoid wing of the palatine (pic). Arrow points to a narrow pocket that opens laterally by the postpalatine fenestra. Each scale bar=5 mm. (ec=ectopterygoid, fp=postpalatine fenestra, in=intemal naris, j=jugal, 1= lacrimal, m=maxilla, mf=maxillary foramen, ml=lateral wall of caudal maxillary sinus, mm=medial wall of caudal maxillary sinus, mp=tooth-like caudomedial process of maxilla, nf=nasal foramen, pl=palatine, pla=ascending wing of palatine, pIc=choanal conch (pterygoid wing) of palatine, plm=maxillary process of palatine, pm=premaxilla, pt=pterygoid, s= openings to caudal maxillary sinus, v=vomer.) soventrally: its dorsal vault fits in the ventral trough of the pterygoid and appears to be partly fused with that bone. The rostromedial comer of the wing probably formed a diminutive Pic 313 counterpart of the vomeral process of other theropods (Elzanowski and Wellnhofer, 1993, fig. 4), as in Oviraptorphiloceratops (Barsbold et al., 1990, fig. 10.ID). Laterally, the palatine

B<br />

FIGURE 2.—Oviraptorid specimen ZPAL MgD-I/95: A, upper jaw in lateral view; B, lateral wall of the choana in<br />

medial view, with a schematic reconstruction of the pterygoid wing of the palatine (pic). Arrow points to a narrow<br />

pocket that opens laterally by the postpalatine fenestra. Each scale bar=5 mm. (ec=ectopterygoid,<br />

fp=postpalatine fenestra, in=intemal naris, j=jugal, 1= lacrimal, m=maxilla, mf=maxillary foramen, ml=lateral<br />

wall of caudal maxillary sinus, mm=medial wall of caudal maxillary sinus, mp=tooth-like caudomedial process<br />

of maxilla, nf=nasal foramen, pl=palatine, pla=ascending wing of palatine, pIc=choanal conch (pterygoid wing)<br />

of palatine, plm=maxillary process of palatine, pm=premaxilla, pt=pterygoid, s= openings to caudal maxillary<br />

sinus, v=vomer.)<br />

soventrally: its dorsal vault fits in the ventral trough of the<br />

pterygoid and appears to be partly fused with that bone. The<br />

rostromedial comer of the wing probably formed a diminutive<br />

Pic<br />

313<br />

counterpart of the vomeral process of other theropods (Elzanowski<br />

and Wellnhofer, 1993, fig. 4), as in Oviraptorphiloceratops<br />

(Barsbold et al., 1990, fig. 10.ID). Laterally, the palatine

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