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18 SOCIETY OF VERTEBRATE PALEONTOLOGY, MEMOIR 3<br />
X can nasolac<br />
I\<br />
pneu fen suborb<br />
nas<br />
ap caud<br />
can<br />
1 cm<br />
proc max 4," fac a i max -<br />
FIGURE 12. Plateosaurus engelhardti, facial skeleton. A, reconstruction<br />
<strong>of</strong> snout in left lateral view. B, same in ventral view. C, right nasal<br />
<strong>of</strong> AMNH 6810 in ventromedial view. D, stereophotographs and interpretive<br />
drawing <strong>of</strong> right maxilla, lacrimal, and palatine <strong>of</strong> AMNH 6810<br />
in dorsal and somewhat medial view. The nasal recess shown in C caps<br />
the hiatus in D. A,B modified after Galton (1990).<br />
I<br />
i~ In can<br />
jUY neurovas int<br />
FIGURE 11. Iguanodon atherjieldensis, facial skeleton. A, Snout in<br />
left lateral view (modified from Noman,1986). B, left maxilla, jugal,<br />
lacrimal, and prefrontal <strong>of</strong> BMNH R5764 in medial view. Arrow shows<br />
the course <strong>of</strong> the nasolacrimal duct.<br />
tending into the premaxillae as well. These foramina and canals<br />
likely conveyed branches <strong>of</strong> the maxillary nerve and accompanying<br />
vessels. Their positions dorsal or dorsolateral to the<br />
putative muscular fossa on the palatine are consistent with the<br />
dorsal pterygoideus muscle being restricted to the floor <strong>of</strong> the<br />
antorbital cavity.<br />
Dinosauria-Among Omithodira, comparable data are abundant<br />
for dinosaurs, but less so for other taxa. Good material is<br />
available for the basal members <strong>of</strong> many <strong>of</strong> the major clades<br />
<strong>of</strong> Ornithischia (Sereno, 1986). The basal omithischian Leso-<br />
thesaurus diagnosticus (Weishampel and Witmer, 1990a; Sereno,<br />
1991a) provides information on both the existence and<br />
position <strong>of</strong> a dorsal pterygoideus and the course <strong>of</strong> the maxillary<br />
neurovasculature. The dorsal surface <strong>of</strong> the palatine<br />
(BMNH R8501, RUB17) has a well developed excavation extending<br />
rostrally up to the lateral aspect <strong>of</strong> the choana (Fig. 7C,<br />
D). This excavation is here interpreted as a muscular fossa and<br />
is bounded rostrally .by a strong ridge that extends from the<br />
maxillary contact (where it borders the choana) rostrodorsomedially<br />
to the contact with the vomer. The palatine (BMNH<br />
RUB17) has an additional deep fossa rostral to this ridge and<br />
dorsomedial to the choana and directly opposite the internal<br />
antorbital fenestra that must be associated with either the nasal<br />
or antorbital cavity. The muscular fossa is restricted to the caudoventral<br />
portion <strong>of</strong> the antorbital cavity. The proximity <strong>of</strong> the<br />
ridge bordering the fossa to the medial edge <strong>of</strong> the lacrimoprefrontal<br />
wall (BMNH R8501) suggests that the postnasal fenestra<br />
was narrow in this area and would make rostral passage <strong>of</strong> a<br />
muscular slip unlikely. The course <strong>of</strong> the maxillary neurovas-