THE UNIVERSITY OF CALGARY Eric Snively A ... - Ohio University

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anterodorsal rotation of the distal portion of MT III, bending strains ancentrated in the region of the proximal splint were probably greater than the bone coutd withstand without breaking. As with results mm the previaus analysis, specific strain magnitudes are difiÏcult to ascertain from MARC'S visualized output. However, strain energy concentration shown (Figure 4.6) implies that ligaments were necessary to prevent MT III fiom breaking under the angled loading regime. Taphonomic evidence strikingly demonstrates the strength of ligamentous articulation in tyrannosaurid metatarsi (Philip Cume, personal communication 2000). Despite their proximal gracility, fradured and healed arctometatarsalian MT III are unknown in the fossil record. This indicates that some strong mechanism prevented the elements from breaking. ln contrast, tyrannosaurid fibulae are often found with healed breaks. This bone is more robust than the proximal splint of MT 111. Logically, we would expect to find more broken tyrannosaurid third metatarsals than fibulae, unless connedive tissues of the metatarsus were absorbing locomotor stress. Tyrannosaurid metatarsi are usually found intact even when the rest of the skeleton is disarticulated. The specimen from which this metatarsus was taken, TMP 94.12.602, was incomplete, with bones scattered over a wide area. 60th metatarsi were found intact, indicating that interrnetatarsal ligaments may have been stronger, and slower to degenerate, than other soft tissues (Philip Currie, personal communication 2000). The extent and orientation of these Iigaments ties in with putative function suggested by bone strain data.
Specifically, osteological correlates of ligaments along the plantar angulation of articulating metatarsals (Chapter 3) have a great deal of surface area evident in anterior or posterior view. This suggests strong resistance to anterior displacement of MT III, which would presumably prevent breakage of the bone. The resulting damping function of ligaments augments the tensional keystone hypothesis, but does not support or contradict the distal unification of metatarsals proposed under that model. Finite element analyses that directly incorporate ligaments will be the subject of future investigation, and will corroborate or falsify the specific kinematics of the model. An example of the encompassing importance of ligament and tendon studies is now discussed, in light of their implications for the present study. Dynarnic versus static loading: are locomotor force estimates for Gorgosaurus libratus tao low? Estimates for footfall forces in G. libratus assumed momentarily static loading on the femur, epipodium, and metatarsus, imposing instantaneous bending loads on the elements. However, the distribution of strain energies in both bone and connective tissue must be wnsidered. If a limb element is held rigid while torque is applied and tendons and ligaments do not defiect, the bone must absorb the full energies of the load. Storage and retum of elastic strain energy becomes much more effective at large body sizes, because tendon and ligament cross sections scale proportionally lower with increasing body mass (Clark and Alexander 1975, Alexander et al. 1979, Pollock 1991). Conservation of energy predicts that if connecüve elements such as the tendons of extensor muscles are
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THE UNIVERSITY OF CALGARY Functiona
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Many figures in this thesis use col
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ACKNOWLEûGEM ENTS Many friends and
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Approval page Acknowledgements Tabi
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CONCLUDING COMMENTS Figures for Cha
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CHAPTER 5: Mechanical and phylogene
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LIST OF FIGURES Figure 1 .l. Phylog
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Figure 3.6. Osteological correlates
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AMNH GI HMN IVPP MOR NMC OMNH PIN P
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and constructional morphology revea
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1985, Bryant and Seymour 1990). If
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surfaces of a Tyrannosaurus rex spe
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3. Troodontidae (Figure 1.2): Trwdo
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Hypothesized functions of the tyran
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1. Atomization (Chapters 2 and 3).
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Figure 1.1. P hylogenetic diagram o
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Figure 1.2. Phylogenetic diagram of
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Figure 1 .S. Skeletal restorations
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did not quantify the degree of prox
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qualitative debate over arctometata
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This hypothesis focuses on tyrannos
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Table 2.1. Theropod and Plafeosauru
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specimens in the figures reflects a
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were not attempted. While this limi
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Chapter 3). 1 now address variation
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- Ç6'P 1 68'€tr 1 L'OC 99'66 L'9
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Table 2.3: Log-transformed values f
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experiences a sharp laterally indin
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ecause it can be cursorily dassifie
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arctometatarsalian specimens, the l
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) Shaf€ and region of proximal ar
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a) Ginglymus. Figure 2.14 shows the
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) Shaft and region of proximal arti
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measurements of width pV2S%TU-DE an
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Table 2.4b Variancelmeasurement eac
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the largest sum of linear measureme
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Table 2.5: Specimen statistics Herr
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and Sinraptor dongi specimens. With
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In addition, a hook like proximal a
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oth physical narrowing and elongati
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1s the MT 111 shape segregation fun
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tyrannosaurids, ornithomimid, and t
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proximal constriction, white EImisa
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Figure 2.2. Tyrannosaurid, trwdonti
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Figure 2.4. Dromaeosaurid and carno
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- Anterior (flexor) surface medial
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Figure 2.7. Left MT III of Tyrannos
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Figure 2.8. Left MT III of Gorgosau
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Figure 2.9. Left MT III of an omith
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Figure 2.10. Left metatarsus of Tmd
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Figure 2.1 1. Left MT III of Elmisa
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Figure 2.12. Right MT III of Deinon
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Figure 2.13. Left MT III of Allosau
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Figure 2.14. Left metatarsus of Sin
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Figure 2.15. Plots of MT Ill specir
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Figure 2.16. Plot of third metatars
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tv . ... . Ri. . . .
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Figure 2.19. Plot of third metatars
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CHAPTER 3: Tensile keystone model o
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dynamically transmitted Iommotor fo
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Table 3.1 . Metatarsi examined in t
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interrnetatarsal dynamics in these
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compelled analysis of movement evid
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Once prepared, TMP 94.1 2.602 and i
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Daspletosaurus tomsus (MOR 590), an
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2. Freedom of movement inferred fro
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Table 3.2. Surface areas of intemet
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phylogenetic bracketing Wtmer 1995)
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4) Forces from anterior displacerne
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e expected for tyrannosaurid interm
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The preceding discussion derives fr
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weapons sparring), and the arctomet
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Figure 3.1. Schematic representatio
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Figure 3.3. CT reconstruction of ri
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Figure 3.5. MT II (left element) an
Page 171: Figure 3.7. Osteological correlates
Page 175: Figure 3.9. Osteological correlates
Page 179: Figure 3.1 1 ae. The metatarsal rec
Page 187: Figure 3.13. Ligament contribution
Page 191 and 192: Figure 3.15. Anatorny of the equid
Page 193: Figure 3.16. Cornparison of loading
Page 196 and 197: (nodes), and solving stresslstrain
Page 198 and 199: The practicality of the finite elem
Page 200 and 201: collective density of trabeculae (K
Page 202 and 203: A FORCE INPUTS AND MATERIAL PROPERT
Page 204 and 205: Alexander et al. (1 979) rewrded a
Page 206 and 207: The preceding loading regime entait
Page 208 and 209: detemined by using the photographic
Page 210 and 211: 2. Preparation of data for contour
Page 212 and 213: . - Elastic modulus (GP4 Ex EY Ez P
Page 214 and 215: conversion. Volume-to-nuages facili
Page 216 and 217: maintained. An angle of 2 degrees p
Page 218 and 219: of MT III (Figure 4.4, pinpointed b
Page 222 and 223: allowed to stretch slightly under t
Page 224: Figure 4.1. Initial loads and bound
Page 228: Figure 4.3. Finite element mesh of
Page 232: Figure 4.5. Strain distribution in
Page 236 and 237: CHAPTER 5: Mechanical and evolution
Page 238 and 239: y distal intermetatarsal ligaments,
Page 240 and 241: Probable fundion of the tyrannosaur
Page 242 and 243: Ornitholestes, and camosaurs) incre
Page 244 and 245: morphology matches in degree the co
Page 246 and 247: discussion elucidates the evolution
Page 248 and 249: face of the skull met part of the m
Page 250 and 251: Alternately, a morphological novelt
Page 252 and 253: outgroup to ail theropods, and the
Page 254 and 255: convincingly evident in figures of
Page 256 and 257: parsimonious scenarios are outlined
Page 258 and 259: dromaeosaurids], and a dade compris
Page 260 and 261: arctometatarsalian forrns. The conv
Page 262 and 263: Proximal intermetatarsal ligaments
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Page 267: Figure 5.2. Phylogeny of the Therop
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Figure 5.4. Phylogeny of the Therop
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Figure 5.6. Phylogeny of the Therop
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Bock W.J. and von Wahlert G. Evolut
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Cume P.J. 1997. Theropoda. In: Fari
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Grenard S. 1991. Handbook of Alliga
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Liem K.F. and Osse J.W.M. 1975. Bio
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Richtsmeier J.T. and Cheverud J.M.
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Woo S., Maynard J., Butler O. 1987.
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Different variables in a PCA will h
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