THE FIRST MONODOMINANT HADROSAUR BONEBED FROM THE OLDMAN FORMATION (CAMPANIAN) OF ALBERTA by EVAN E. SCOTT Submitted in partial fulfillment of the requirements for the degree of Master of Science Department of Earth, Environmental, and Planetary Sciences CASE WESTERN RESERVE UNIVERSITY August, 2015 CASE WESTERN RESERVE UNIVERSITY SCHOOL OF GRADUATE STUDIES We hereby approve the thesis of Evan E. Scott candidate for the degree of Masters of Science*. Committee Chair Beverly Saylor Committee Member Peter McCall Committee Member Michael Ryan Date of Defense May 21, 2015 *We also certify that written approval has been obtained for any proprietary material contained therein. 2 TABLE OF CONTENTS 1. INTRODUCTION Project Rationale 11 Hadrosauridae 12 Bonebeds 14 Histology 17 2. MATERIALS AND METHODS Field Methods 22 Laboratory Methods 26 3. REGIONAL AND LOCAL GEOLOGY Regional Geology 28 Local Geology 29 4. CRANIAL AND POSTCRANIAL ANATOMY 32 5. TAPHONOMY Taxonomic Composition of Wendy’s Bone Bed 48 Taphonomic Modifications 48 Relative Age Profile of Wendy’s Bone Bed 54 6. HISTOLOGICAL DESCRIPTIONS 60 7. DISCUSSION Taphonomy 68 Histology 75 Histological Age Profile 77 Bone texture as a possible indicator of ontogenetic stage 80 Sociality 81 Conclusions 82 APPENDICES Appendix A: Histological Preparation 84 3 REFERENCES 89 4 TABLES Table 1. Summary of measurements and histological observations for sectioned WBB tibiae. 27 Table 2. Summary of taphonomic data. 53 5 FIGURES Figure 1. Representative histological cross section. 21 Figure 2. Map of southern Alberta and its geographic relationship to the rest of Canada. 23 Figure 3. Panorama of field locality. Inset: close-up of WBB quarry. 24 Figure 4. Quarry map and rose diagrams displaying orientation data. 25 Figure 5. Regional stratigraphy of the Belly River Group, and stratigraphy local to the WBB. 31 Figure 6. Diagrammatic representation of Gryposaurus cranial elements recovered from the WBB. 35 Figure 7. Representative Gryposaurus dentaries from the WBB. 36 Figure 8. Representative Gryposaurus pelvic elements from the WBB. 37 Figure 9. Representative Gryposaurus appendicular elements from the WBB. 38 Figure 10. Gryposaurus cranial elements from the WBB. 40 Figure 11. Tibia specimen TMP2008.045.0064. 42 Figure 12. Tibia specimen TMP2009.038.0008. 43 Figure 13. Tibia specimen TMP2014.078.0014. 44 Figure 14. Tibia specimen TMP2009.038.0032. 45 6 Figure 15. Tibia specimen TMP2010.078.0022. 46 Figure 16. Tibia specimen TMP2010.078.0012. 47 Figure 17. Taphonomic breakage. 57 Figure 18. Taphonomic fracture patterns. 58 Figure 19. Taphonomic abrasion. 59 Figure 20. Histology of late juvenile gryposaurs from the WBB. 63 Figure 21. Histology of early juvenile gryposaurs from the WBB. 66 Figure 22. Skeletal diagram displaying relative abundance of skeletal elements in the WBB. 73 7 ACKNOWLEDGEMENTS I would like to thank the Southern Alberta Dinosaur Project, The Royal Ontario Museum, The Royal Tyrrell Museum of Palaeontology, and the Cleveland Museum of Natural History for helping to facilitate my participation in fossil excavation and collection in the field and for providing access to laboratory facilities during all phases of my project. I am indebted to the Dinosaur Research Institute and to the Women’s Committee of the Cleveland Museum of Natural History for providing generous financial support for my research. I would like to thank my graduate committee—Beverly Saylor, Michael Ryan, Peter McCall—as well as Darin Croft and Scott Simpson, for guidance throughout the various stages of my graduate career. I also owe a great deal of thanks to my friends and colleagues at the Royal Ontario Museum—Kirstin Brink, Kentaro Chiba, Thomas Cullen, Mateusz Wosik, Brian Iwama, Ian Morrison, Kevin Seymour, and David Evans—for their help and patience in transforming me into a capable histological preparator. I am grateful to Wendy Sloboda for discovering the bonebed and Nic Campione for teaching me the basics of fossil excavation in the field. David Saja, Gary Jackson, and David Chapman all provided valuable assistance and advice while working in the Mineralogy and Vertebrate Paleontology departments at the Cleveland Museum of Natural History. Laura Dempsey provided invaluable support with photography of specimens. 8 I would also like to thank Tara Kelloway, Douglas Dunn, and Joseph Hannibal for valuable conversations on my research and for much needed laughter. 9 The First Monodominant Hadrosaur Bonebed from the Oldman Formation (Campanian) of Alberta by EVAN E. SCOTT Abstract A monodominant Gryposaurus bonebed located in the Oldman Formation (Campanian) of southern Alberta represents a parautochthonous assemblage of juvenile-sized individuals that are preserved in a fine-grained mudstone within an overbank sequence. Histological examination of six tibiae confirms the diagnosis of all individuals as juveniles, although histological variability indicative of two age classes within the bonebed suggests that members did not all originate from the same brood. Bone microstructure data indicates that these gryposaurs experienced rapid growth and achieved approximately 70% of adult size before the end of their second year. The parautochthonous nature of the bonebed, and the lack of small neotate material and large adult material, suggests that the bonebed represents an isolated group of juveniles. This group may have separated itself from a larger social grouping, possibly as an evolutionary strategy to allow greater allocation of resources to altricial hatchlings. 10 CHAPTER I. INTRODUCTION Project Rationale The Late Cretaceous sediments of Alberta, Canada, have been historically recognized for their impressive yield of vertebrate fossils (Currie and Koppelhus 2005). Beginning with the Great Canadian Dinosaur Rush of the late nineteenth and early twentieth centuries [e.g., Lawrence Lambe (1849–1934), Barnum Brown (1873–1963), Charles Sternberg (1885–1981)], and continuing until the late 1970's, prospecting efforts resulted in many museums across North America and the United Kingdom acquiring impressive collections of Canadian dinosaurs. Vertebrate paleontological collection and research programs continue to this day in Alberta, although the Alberta Historical Resources Act (1978) dictates that ownership of all fossils is now retained by the province. The Southern Alberta Dinosaur Project (SADP) was initiated in 2005 by the Cleveland Museum of Natural History and the Royal Ontario Museum to intensely sample and collect dinosaurs, and other vertebrates, from the dinosaur-bearing outcrops of southern Alberta (i.e., the Belly River Group and the Milk River Formation). To date, the project has discovered and collected multiple new dinosaur-bearing localities, including articulated skeletons and bonebeds (e.g., Ryan and Russell 2005; Ryan 2007; Ryan et al. 2012; Evans et al. 2013; Scott et al. 2014). 11 This project is a taphonomic and histological investigation of the first documented hadrosaurid bonebed from the Oldman Formation of the Belly River Group of Alberta. The locality, 'Wendy’s Bone Bed' (WBB), is named after its discoverer, Wendy Sloboda. The project goals are: 1. To document the taphonomic history of the bonebed. 2. To determine the age at time of death and establish an age profile, if possible, of the hadrosaurid material preserved in the bonebed by histologically sectioning a representative sample of tibiae. 3. To determine if the data derived from the bonebed can be used to provide information on social and post-hatchling behavior in North American hadrosaurs. Institutional abbreviations: CMNH—Cleveland Museum of Natural History; ROM—Royal Ontario Museum (Toronto, Ontario); TMP—Royal Tyrrell Museum of Palaeontology (Drumheller, Alberta). Hadrosauridae Hadrosauridae is a diverse family of large-bodied ornithischian herbivores that flourished during the Late Cretaceous (Horner et al. 2004; Eberth and Evans 2014). They are commonly known as the “duck-bill” dinosaurs due to their edentulous, flared rostra. Hadrosaurs were some of the largest terrestrial herbivores of the Late Cretaceous with head-to-tail lengths in some taxa exceeding 10 meters (Varricchio and Horner 1993; Fiorillo and Gangloff 2001), and skull lengths exceeding one meter (Campione and Evans 12 2011; Eberth and Evans 2011). Hadrosaurs also provide some of the best examples of dinosaur nests, babies, eggs, and embryos currently known (Horner and Makela 1979; Horner 1982; Horner, 1999). Hadrosaurs enjoyed a wide distribution, with fossil localities known from Antarctica, Asia, Europe, and North and South America, ranging from temperate coastal (i.e., the western interior of North America) to seasonally cooler arctic environments (i.e., the North Slope of Alaska) (Chinsamy et al. 2012). Competing hypotheses have suggested either a North American (Head 1998; Horner et al. 2004) or Asian (Godefroit et al. 2003; You et al. 2003) origin for the clade. In North America, hadrosaurs from the Campanian to the end of the Maastrichtian have north-south, west-east distributions from Alaska (Brouwers et al. 1987; Davies 1987; Chinsamy et al. 2012) to Mexico (Kirkland et al. 2006), and California (Morris 1973; Bell and Evans 2010) to New Jersey (Colbert 1948; Gallagher 1997), respectively. Two clades (subfamilies) have historically been recognized within the Hadrosauridae: the crestless or solid-crested Hadrosaurinae, and the hollow-crested Lambeosaurinae. Prieto-Márquez (2010) redefined the Hadrosaurinae as only including the type species, Hadrosaurus