text-fig. 17. Lateral view of the braincase, illustrating states for several braincase characters, a, basal ornithischian Lesothosaurus diagnosticus; redrawn from Sereno (1991Z?). B, Troödon formosus; based on Currie and Zhao (1993a); the paroccipital process of Troödon is shown in cross-section to illustrate the internal pneumatic cavity within this bone. Abbreviations: atr, anterior tympanic recess; bpt, basipterygoid process; boc, basioccipital; bsp, basisphenoid; bt, basal tuber; ep, episthotic; f, frontal; fo, fenestra ovalis; ic, foramen for the entrance of the vidian canal for the internal carotid; jf, jugular foramen; Is, laterosphenoid; mf, metotic fissure; o, orbital facet on the frontal; oc, occipital condyle; op, opisthotic; osp, orbitosphenoid; pa, parietal; pn, pneumatic openings or cavities; pop, paroccipital process; pro, prootic; ps, parasphenoid; pspc, parasphenoid capsule; ptf, posttemporal foramen; vcm, exit of the vena capitis medialis; Roman numbers refer to the foramina for the exits of cranial nerves. Scale bars represent 10 mm. in The interrelationships and evolution of basal theropod dinosaurs

text-fig. 17. Lateral view of the braincase, illustrating states for several braincase characters, a, basal ornithischian Lesothosaurus diagnosticus; redrawn from Sereno (1991Z?). B, Troödon formosus; based on Currie and Zhao (1993a); the paroccipital process of Troödon is shown in cross-section to illustrate the internal pneumatic cavity within this bone. Abbreviations: atr, anterior tympanic recess; bpt, basipterygoid process; boc, basioccipital; bsp, basisphenoid; bt, basal tuber; ep, episthotic; f, frontal; fo, fenestra ovalis; ic, foramen for the entrance of the vidian canal for the internal carotid; jf, jugular foramen; Is, laterosphenoid; mf, metotic fissure; o, orbital facet on the frontal; oc, occipital condyle; op, opisthotic; osp, orbitosphenoid; pa, parietal; pn, pneumatic openings or cavities; pop, paroccipital process; pro, prootic; ps, parasphenoid; pspc, parasphenoid capsule; ptf, posttemporal foramen; vcm, exit of the vena capitis medialis; Roman numbers refer to the foramina for the exits of cranial nerves. Scale bars represent 10 mm.