Fig. 10 Baryonyx walkeri, holotype, BMNH R9951; left jugal. A, lateral view; B, medial. x 0.5. 
right angled corner. The ventral margin is rounded so that it would 
appear U-shaped in transverse section. Viewed from either side, the 
dorsal margin is bent significantly upwards as it approaches the 
anterior end: at about the level of the 9" tooth alveolus it is angled 
upwards through some 25° and then runs in a more or less straight 
line to the anterodorsal corner of the bone, 1.e. to the region of the 1* 
tooth. Forwards of the level of the 9" alveolus the dentary starts to 
expand both vertically and laterally (thereby creating the enlarged 
‘terminal rosette’ ). 
The ventral margin, at the extreme anterior end, passes smoothly 
into the anterior margin. This region is where the two rami, left and 
right, joined at the mandibular symphysis. The symphysial surface, 
sq 
Fig. 11 
Baryonyx walkeri, holotype, BMNH R9951; left quadrate. A, lateral view; B, posterior; C, ventral. 
A.J. CHARIG AND A.C. MILNER 
however, is marked by only a very few short parallel striations on the » | 
lingual side of the dentary, suggesting that the symphysis must have 
been effected through connective tissue only, retaining some mobil- 
ity between the two jaw rami. 
The posterior third of the dentary is altogether much thinner than} 
the anterior part; it has a broader, blade-like appearance, expanded 
vertically, with the dorsal and ventral margins diverging widely 
posteriorly. Indeed, the Meckelian groove on its lingual surface © 
widens backwards to the extent that it disappears into a broad, flat)” 
surface occupying the entire height of the bone between the dorsal 
and ventral rims. The labial surface is flat and featureless. 
The dorsal and ventral margins of this posterior dentary ‘blade’ 
xiOi5: 
