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

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Alternately, a morphological novelty can yield convergence upon a single functional outcome by multiple modifications of the original structure. Gekkonine and diplodadyline geckos display parallelisrn in the occurrence and structure of subdigital adhesive pads (Russell 1979b). The specific morphology, which enables these lizards to cling to surfaces, diïers in closely related clades. The common denominator in development of adhesive pads in geckos is a spinose Oberhautchen, or outer integumentary layer with spines. Outgroup comparison indicates that the spines have independently evoIved into adhesive setae in several distantly related dades of geckos. Marphologically generalized spines are retrospectively identifiable as a key innovation that facilitated the ernergence of parallelism (Russell 1979b). The original shared structure has become modified for the same function several times, along multiple evolutionary pathways (8ock 1965). The evolution of the arctometatarsus, and its ernergence andor loss in several coelurosaurian taxa, may also have proœeded along multiple pathways. Intermetatarsal ligaments, indicated by rugosity on the articular surfaces, would be a necessary precursor to distal ligament expansion involved in tensile keystone dynamics. In this way, multiple elaborations of theropod intermetatarsal ligaments may have paralleled specializations of the spinose Oberhautchen of geckos. It is hypothesized, therefore, that these ligaments were the prerequisite key innovation common to dramatic parallelisms in foot morphology that occurred in coelurosaurs.
This and other systernatically infomed hypotheses are testable by mapping characters ont0 a well-supported phylogeny of theropods, and determining temporal polarization of charaders through parsimony. The distribution of the arctometatarsus on a phylogeny, for instance, allows us to predict the occurrence of associated features, including intwmetatarsal ligaments and an elongate metapodium. Additionally, phylogenetic testing can illuminate the evolution of selective utility of the arctometatarsus: What selecüon pressures led to the fixation of the arctometatarsus when it arose? The following discussion therefore details pathways of possible evolutionary emergence of the arctometatarsus, in the hopes of testing hypotheses of origin and utility. Implications of phylogenefic disfribution of the arcfornetatarsus The presence or absence of an arctometatarsus, and intermetatarsal ligament correlates, serve as character states that can be mapped ont0 two competing but wellcorroborated theropod phylogenies (Cume and Padian 1997 and Holtz 2000; Sereno 1999). The phytogenies summarize the relationships of taxa bearing an arctometatarsus, and reveal aie distribution of intermetatarsal ligaments, the arctometatarsus, and trophic habit in coelurosaurs and their sister taxa. The taxa in these phylogenies primarily include those investigated in the Principal Components Analysis in Chapter 2. Inclusion of a taon in Figure 2.16 designates it as arctometatarsafian; the Cretaceous Mongolian bird Mononychus (Chiappe 1997). which was unavailable for examination, is also scored as such (Holtr 1994b. Sereno 1999). The sauropodomorph Plateosaurus serves as the
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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
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Figure 3.1 1 ae. The metatarsal rec
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Figure 3.13. Ligament contribution
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Figure 3.15. Anatorny of the equid
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Figure 3.16. Cornparison of loading
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(nodes), and solving stresslstrain
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The practicality of the finite elem
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Page 202 and 203: A FORCE INPUTS AND MATERIAL PROPERT
Page 204 and 205: Alexander et al. (1 979) rewrded a
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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
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Page 248 and 249: face of the skull met part of the m
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Page 258 and 259: dromaeosaurids], and a dade compris
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Page 262 and 263: Proximal intermetatarsal ligaments
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Page 267: Figure 5.2. Phylogeny of the Therop
Page 278 and 279: Bock W.J. and von Wahlert G. Evolut
Page 280 and 281: Cume P.J. 1997. Theropoda. In: Fari
Page 282 and 283: Grenard S. 1991. Handbook of Alliga
Page 284 and 285: Liem K.F. and Osse J.W.M. 1975. Bio
Page 286 and 287: Richtsmeier J.T. and Cheverud J.M.
Page 288 and 289: Woo S., Maynard J., Butler O. 1987.
Page 290 and 291: Different variables in a PCA will h
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THE UNIVERSITY OF CALGARY Eric Snively A ... - Ohio University

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