The Cranial Morphology of Tyrannosaurus rex
Fig. 1. Tyrannosaurus rex Osborn, LACM 23844, right premaxilla. — A. Medial view. B. Posterior view. C. Lateral view. D. Ventral view. Dotted lines indicate broken nasal process. 0.3 X.
Plate 1 Tyrannosaurus rex Osborn, Hell Creek Fm., Jordan (Montana), LACM 23844. Fig. 1. Right lachrymal in lateral view. Fig, 2. Right lachrymal in medial view. The medial wall of the posterior part ofthe horizontal ramus is missing, revealing the internal chambers. Fig. 3. Right premaxilla in lateral view. The lateral tooth (arrow) has apparently been broken, after which the broken surface was planed off. Fig. 4. Left quadratojugal in medial view. The articular surfaces for the quadrate are seen at the left. Fig. 5. Left quadratojugal in lateral view. Scale bars 10 cm.
Plate I. Complete skull of Tyrannosaurus rex Osborn. Amer. Mus. No. 5027. One-fifth natural size. The element shown in the upper posterior part of the first antorbital fenestra is the displaced ectopterygoid (transversum) of the opposite side.
Plate II. Tyrannosaurus rex. Superior view of skull. Amer. Mus. No. 5027. Scale about 1/6.
Fig. 6. Tyrannosaurus rex. Inferior aspect of the skull, slightly corrected for distortion. Amer. Mus. No. 5027. Scale i. The ectopterygoids, Ec. pt., have slipped back from the normal connection with the maxillaries.
Plate 2. Tyrannosaurus rex Osborn, Hell Creek Fm., Jordan (Montana) (LACM 23844) and Custer (Montana) (MOR 008). Fig. 1. Right maxilla of LACM 23844 in medial view. Anterodorsal and posterodorsal to the maxillary fenestra the medial walls of the internal chambers are missing, so that they are exposed to view. Only the posterior part of the palatal process is preserved. Fig. 2. Right squamosal of MOR 008 in dorsal view. Anterior is to the left. Fig. 3. Right squamosal of MOR 008 in ventral view. Anterior is to the right. Scale bars 10 cm.
Plate 1. Complete skull of Tyrannosaurus rex Osborn. Amer. Mus. No. 5027. One-fifth natural size. The element shown in the upper posterior part of the first antorbital fenestra is the displaced ectopterygoid (transversum) of the opposite side.
Fig. 22. Tyrannosaurus rex. Left maxilla, outer view. Amer. Mus. No. 973. (Type.) Scale 1/6
Fig. 23. Tyrannosaurus rex. Left maxilla, inner view of the same specimen, Amer. Mus. No. 973. Exhibiting eight of the maxillary teeth, four vacant alveoli, and nine interdental plates of the maxilla
Fig. 2. Tyrannosaurus rex Osborn, LACM 23844, right maxilla represented diagramatically in medial view. — The exposed sinus chambers may be seen just anterodorsal (a, b and c; the anteriormost is not lettered) and posterodorsal (d) to the maxillary fenestra. The presumed tooth impressions (1, 2 and 3) may also be seen anteriorly, just below the. broken palatal process. 0.3x.
Fig. 3. Tyrannosaurus rex Osborn, LACM 23844, right lachrymal represented diagramatically in medial view. — The upper sinus chambers are exposed, and the chamber in the descending ramus is indicated by dot- ted lines. The position of the lateral foramen is also indicated in dotted line. 0.3 X.
Plate 3. Tyrannosaurus rex Osborn, Hell Creek Fm., Jordan (Montana) (LACM 23844) and Custer (Montana) (MOR 008). Fig. 1. Anterior part of left nasal of MOR 008 in lateral view, showing the prominent nasal rugosities. Fig. 2. Left jugal of LACM 23844 in lateral view. Fig.3. Left jugal of LACM 23844 in medial view. Part of the medial wall of the vertical internal canal is missing, revealing the vertical canal. Scale bars 10 cm.
Plate 4 Tyrannosaurus rex Osborn, Hell Creek Fm., Jordan (Montana) (LACM 23844) and Custer (Montana) (MOR 008) Fig. 1. Right postorbital of LACM 23844 in lateral view. Fig. 2. Right postorbital of LACM 23844 in medial view. Fig. 3. Left postorbital of MOR 008 in lateral view. The prominent eave-like projection over the orbit of MOR 008 may be seen, as well as the low roughening in that area in LACM 23844. Scale bars 10 cm.
Fig. 1. Skull of Tryrannosaurus. d, dentary; sur, surangular; sq, squamosal; prf,prefrontal; o, orbit; na, anterior nares; 1, 2, 3, antorbital openings. Dotted outlines arefrom Allosaurus.
Plate 5. Tyrannosaurus rex Osborn, Hell Creek Fm., Jordan (Montana), AMNH 5027 and LACM 23844. Fig. 1. Right jugal of LACM 23844 in ventral view, showing the presumed articular surface for the ectopterygoid (arrows). Fig. 2. Right jugal of LACM 23844 in lateral view, showing the articular surface for the lachrymal adjacent to scale bar. Fig. 3. Dorsal portion of left lateral temporal fenestra of AMNH 5027 in lateral view, showing the smooth surface (just in front of the “Sq.”) interpreted as an attachment area for the external mandibular adductors. Scale bars 10 cm.
Figure 7 Daspletosaurus torosus, reconstruction of the skull in dorsal aspect, based on NMC 8506
Fig. 4. Tyrannosaurus rex Osborn, LACM 23844, left jugal in lateral view. — The presumed extent of the internal chambers is shown in dotted line. The medial foramen also so indicated, at the end of the short passage directed posterodorsally from the area of the lateral foramen. 0.3 X.
Fig. 5. Tyrannosaurus rex Osborn, reconstruction of the vomer. — A. Left lateral view. B. Ventral view. The extreme posterior portion is unknown. The insets indicate which parts of the reconstruction are based on LACM 23844 and which on MOR 008. Scale bar 10 cm
Plate 6 Tyrannosaurus rex Osborn, Hell Creek Fm., Custer (Montana), MOR 008. Fig. 1. Right palatine in lateral view. Fig. 2. Right palatine in ventral view. Fig. 3. Right palatine in dorsal view. The anterolateral portion of this element has been broken away. Scale bars 10 cm.
Plate 7. Tyrannosaurus rex Osborn, Hell Creek Fm., Jordan (Montana) (CM 9379) and Custer (Montana) (MOR 008), and Lance Fm., Converse Co., (Wyoming) (AMNH 5117). Fig. 1. Occipital face of AMNH 5117. Part of the posterior wall of the paroccipital process has collapsed forward into the internal chamber of that process, thus revealing its presence. Fig. 2. Right half of the occipital face of CM 9379. Fig. 3. Left ectopterygoid of MOR 008 in ventral view. Fig. 4. Right ectopterygoid of MOR 008 in dorsal view. Scale bars 10 cm.
Fig. 6. Tyrannosaurus rex Osborn, reconstruction of the right pterygoid. — A. Lateral view. B. Dorsal view. Based on LACM 23844 and MOR 008. The extent and form of the anterior and lateral processes are unknown. Scale bar 10 cm.
Figure 9 Daspletosaurus torosus, reconstruction of the palate in ventral aspect, based on NMC 8506.
Plate 8. Tyrannosaurus rex Osborn, Hell Creek Fm., Jordan (Montana) (LACM 23844), and Lance Fm., Converse Co., (Wyoming) (AMNH 5117). Fig. 1. Right pterygoid of LACM 23844 in posterior view. Fig. 2. Right pterygoid of LACM 23844 in lateral view. Fig. 3. Right pterygoid of LACM 23844 in dorsal view. Fig. 4. Articulated frontals and parietals of AMNH 5117 in dorsal view. Scale bars 10 cm.
Plate 9. Tyrannosaurus rex Osborn, Hell Creek Fm., Jordan (Montana) AMNH 5027. Fig. 1. Right epipterygoid.in anterolateral view. 0.6X. Fig. 2. Right epipterygoid in lateral view. The epipterygoid has been displaced forward in this specimen to lay at the back of the left antorbital fenestra. Abbreviations on. specimen: Ec.pt., ectopterygoid; Ep.pt,, epipterygoid; ‘La’, lachrymal. 0.6 X.
Fig. 3. Tyrannosaurus rex. Full front and oblique front view of skull. Amer. Mus. No. 5027. Greatly reduced. ‘Pr.fr.,’ prefrontal (= lachrymal of mammals, fide Gaupp). ‘La.,’ “ lachrymal” of reptiles (= adlachrymal Gaupp).
Plate 10. Tyrannosaurus rex Osborn, Hell Creek Fm., Jordan (Montana) LACM 23844, Fig, 1. Stereo view of the dorsal articular surface of the quadrate (for the squamosal). Fig. 2. Left quadrate in anteromedial view. The aperture connecting with the internal chambers is visible at lower right, just above the medial articular condyle. Fig. 3. Stereo view of the right surangular in dorsal view, showing facet interpreted as the attachment area for the M. adductor mandibulae externis supeficialis et medialis. Scale bar 10 cm.
Fig. 7. Tyrannosaurus rex Osborn, diagram of right quadrate in anterolateral view. — Based largely on LACM 23844, but also on MOR 008. The known extent and positions of the internal chambers are indicated by dotted lines. 0.3 x.
Plate 11. Tyrannosaurus rex Osborn, Lance Fm., Converse Co. (Wyoming) AMNH 5117. Fig. 1. Braincase in anteroventral view. Fig. 2. Laterosphenoid region of the braincase in oblique lateroventral aspect. Scale bars 10 cm.
Fig. 8. Tyrannosaurus rex. Immature cranium, same as in Fig. 7, full front view. Amer. Mus. No. 5117. Scale 1/3.
Figure 4 Albertosaurus, reconstruction of the lower half of the braincase seen in sagittal section. Abbreviations: CC carotid canal, MED medullary cavity, PIT pituitary fossa, ST sella turcica, VI hypothetical course of sixth cranial nerve. For further explanation see text.
Plate III. Tyrannosaurus rex. Section of skull showing brain cavity. Amer. Mus. No. 5029: Scale 1/2.
Plate 12. Tyrannosaurus rex Osborn, Hell Creek Fm., Jordan (Montana) LACM 23844. Fig. 1. Left dentary in medial view. Fig. 2. Left dentary in lateral view. Scale bar 10 cm.
Plate 13. Tyrannosaurus rex Osborn, Hell Creek Fm., Jordan (Montana) (AMNH 5027 and LACM 23844) and Custer (Montana) (MOR 008). Fig. 1. Stereo view of the right articular of MOR 008 in posterior view, showing the concave posterior face. Fig. 2. Part of the articular surface on the surangular, for the dentary of LACM 23844 in lateral view. Fig. 3. Detail of the dentary-angular contact of AMNH 5027 in lateral view. A metal supporting bracket for the skull passes over this contact. Scale bars 10 cm.
Figure 6 Daspletosaunts torosus, reconstruction of the skull in lateral aspect, based on NMC 8506. The foramen in the quadratojugal is taken from NMC 11315, where the element is better preserved.
Plate 14. Tyrannosaurus rex Osborn, Hell Creek Fm., Jordan (Montana) LACM 23844. Fig. 1. Left splenial, in two pieces not sharing a contact, in lateral view. Fig. 2. Left splenial, in two pieces not sharing a contact, in medial view. Fig. 3. Left prearticular in medial view. Fig. 4. Left prearticular in lateral view. Scale bars 10 cm.
Fig. 18. Tyrannosaurus rex. Inner view of left lower jaw, with the splenial and supradentary (d. p.) plate present. Amer. Mus. No. 5027. for., foramen in surangular. n.f., nutrient foramen. Mck. g., groove for Meckelian cartilage. d. p., supradentary plate (may be an outgrowth of the splenial).
Plate 15. Tyrannosaurus rex Osborn, Hell Creek Fm., Jordan (Montana) LACM 23844. Fig. 1. Right surangular in lateral view. The pit (white arrow) visible in the lateral buttress, just above the surangular fenestra, is apparently the result of an injury sustained during life. Fig. 2. Right surangular in medial view. Fig. 3. Left angular in medial view. Fig. 4. Left angular in lateral view. Fig. 5. Left articular in medial view. Fig. 6. Left articular in dorsal view. Scale bars 10 cm.
Fig. 19. Tyrannosaurus rex. Superior view of articular region of lower jaw. Amer. Mus. No. 5027. hy., groove for hyoid bone.
Text-fig. 2—The articular surface of the frontal for the prefrontal in anterior view. A, Right frontal of Albertosaurus cf. A. lancensis, LACM 23845. B, Left frontal of Tyrannosaurus sp., MMS 51-2004. The diagonal lines indicate broken surfaces. Abbreviations: ec, endocranial cavity; po, articular surface of frontal for postorbital; prf, articular surface of frontal for prefrontal. MMS 51-2004 includes portions of the laterosphenoid and prootic in addition to the frontal. Bars represent 1 cm.
Figure 5 Semidiagrammatic relationships between the exits for cranial nerves II-Vi on the anterior surfaces of the orbitosphenoid and laterosphenoid. A. Albertosaurus libratus, after NMC 11814; B. Daspletosaunis torosus, after NMC 8506
Fig. 9. Tyrannosaurus rex Osborn, reconstruction of the skull in ventral view. A. Ventral aspect as given by Osborn (1912). Positions of the jugal flexure in SDSM 12047 indicated by arrow. B. Reconstruction proposed here. Scale bar 30 cm.