New Insights Into the Brain, Braincase, and Ear Region of Tyrannosaurs (Dinosauria, Theropoda), with Implications for Sensory Organization and Behavior
Fig. 7. Endocranial region of Tyrannosaurus rex (actual fossil specimen of AMNH FR 5029, sagittally sec- tioned) in left medial view to show the fine vascular grooves on the endocranial surface.A, Labeled view show- ing the whole endocranial cavity. B, Close-up view with reversed stereopairs such that the endocranial cavity looks ‘‘filled,’’ making the view more comparable to the digital endocasts illustrated elsewhere in this article.
Fig. 1. Cranial endocast of Tyrannosaurus rex (AMNH FR 5117) reconstructed from CT scans. Some vascular elements and the endosseous labyrinth are depicted. Labeled illustrations in A, left lateral; B, ventral; C, dorsal; D, rostral; and E, caudal views.
Fig. 2. Stereopairs of articulated braincase of Tyrannosaurus rex (AMNH FR 5117) derived from reconstructed CT scans and shown in the following views: A, right lateral; B, dorsal; C, caudal.
Fig. 3. Cranial endocasts reconstructed from CT scans in left lateral view (left column, this page), ventral view (right column, this page), and dorsal view (left column, facing page). A–C, Tyrannosaurus rex (AMNH FR 5117); D–F, T. rex (AMNH FR 5029); G–I, T. rex (FMNH PR2081); J–L, Gorgosaurus libratus (ROM 1247); M–O, Cleveland skull (CMNH 7541; reversed). Some vascular elements are depicted, as well as the endosseous labyrinth. Scale bars = 2 cm.
Fig. 4. Cranial endocasts reconstructed from CT scans in left lateral view, arranged in a cladogram. A, Majungasaurus crenatissimus (FMNH PR2100; modified from Sampson and Witmer, 2007); B, Allosaurus fragilis (UMNH VP 18050); C, Tyrannosaurus rex (AMNH FR 5117); D, Struthiomimus altus (TMP 90.26.1); E, Deinonychus antirrho- pus (composite of MOR 747 and OMNH 50268); and F, Archaeopteryx lithographica (BMNH 37001). C, D, and E+F are arranged in a polytomy to reflect uncertain relationships near the base of Coelurosauria, which impacts the optimization of some attributes (e.g., position of optic lobe). Scale bars = 1 cm.
Fig. 5. Stereopairs of a braincase of Tyrannosaurus rex (AMNH FR 5117) reconstructed from CT scans in various views to show the osteological correlates (e.g., foramina, fossae, crests) of many of the soft-tissue structures discussed in the text. Each view consists of a set of stereopairs (above) showing a semitransparent braincase revealing enclosed soft-tissue structures, coupled with a set of stereopairs (below) in the same view showing the bony braincase and labeled structures. A, left lateral view; B, left lateral view, close-up.
Fig. 6. Olfactory structures in Tyrannosaurus rex. A, FMNH PR2081; B, AMNH FR 5117; dorsal views of the cranial endocast. Green structures in A are the caudal portions of the olfactory region of the nasal cavity, which correspond to what Brochu (2000, 2003) regarded as olfactory bulbs. The true limits of the olfactory bulb cast are indicated in blue of the cranial endocast. C, sagittal section of a T. rex skull, showing the cranial endocast in place (generated by registering AMNH FR 5117 to a one-third scale restored sculpture of FMNH PR2081). The large arrow shows the course of the respiratory airway (yellow) through the rostral portion of the nasal cavity, choana, and pharynx. The small, wavy arrow shows the low-velocity path of odorant molecules through the large olfactory region of the nasal cavity (reddish). Scale bar for A–B = 5 cm.
Fig. 8. Endosseous labyrinths (left sides). Left four columns are stereopairs of left lateral and dorsal views. Right two columns are rostral and caudal views, respectively. A–D, Tyrannosaurus rex (AMNH FR 5029); E–H, T. rex (AMNH FR 5117); I–L, Gorgosaurus libratus (ROM 1247, composite of both sides); M–P, Cleveland skull (CMNH 7541, composite of both sides, restored parts in yellow); Q–T, Struthiomimus altus (AMNH FR 5355); and U–X, Allosaurus fragilis (UMNH VP 18050, right side reversed). All are to the same scale (Scale bar = 1 cm).
Fig. 9. Columella and columellar region. A, braincase of the Cleveland skull (CMNH 7541, extracted from the full CT dataset) in left rostroventrolateral view, showing the left columella preserved in place. B, Cranial endocast and labyrinth of Tyrannosaurus rex (AMNH FR 5117) reconstructed from CT scans in left caudodorsolateral view, with the columellar canal (highlighted in teal) leading toward the fenestra vestibuli of the endosseous labyrinth. Scale bars = 2 cm.
Fig. 10. Pneumatic sinuses in the braincase of tyrannosaurs in right rostroventrolateral view (left column) and caudal view (right column). Bone is rendered semitransparent, revealing pneumatic recesses, cranial endocast, vascular elements, and the endosseous labyrinth. A, Tyrannosaurus rex (AMNH FR 5117); B, Gorgosaurus libratus (ROM 1247); and C, the Cleveland skull (CMNH 7541). Scale bars = 5 cm.
Fig. 11. ‘‘Alert’’ head postures based on orienting the skull such that the lateral semicircular canal is horizontal. A, Majungasaurus crenatissimus (FMNH PR2100; modified from Sampson and Witmer, 2007); B, Allosaurus fragilis (UMNH VP 18050, registered to MOR 693); C, Gorgosaurus libratus (ROM 1247, registered to a cast of AMNH FR 5664); D, the Cleveland skull (CMNH 7541); E, Tyrannosaurus rex AMNH FR 5117, registered to a model of a T. rex skull); F, T. rex (FMNH PR2081); G, Struthiomimus altus (TMP 90.26.1); and H, Troodon formosus (composite of TMP 86.36.457 and TMP 79.8.1, registered to the skull of Saurornithoides junior, IGM 100/1). Scale bars pertain to A–D (top bar), E–F (middle bar), and G–H (lower bar). Scale bars = 10 cm.