THE FIRST MONODOMINANT HADROSAUR BONEBED from the OLDMAN FORMATION (CAMPANIAN) of ALBERTA by EVAN E. SCOTT Submitted in Partial

Home , Bone bed, Brachylophosaurus, Corythosaurus, Dakota (fossil), Edmontosaurus regalis, Foremost Formation

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.

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

REFERENCES 89

TABLES

Table 1. Summary of measurements and histological observations for sectioned WBB tibiae. 27

Table 2. Summary of taphonomic data. 53

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

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

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.

I would also like to thank Tara Kelloway, Douglas Dunn, and Joseph Hannibal for valuable conversations on my research and for much needed laughter.

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.

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).

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

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 foulkii, and erected the subfamily Saurolophinae to include the genera previously included in the Hadrosaurinae. However, this revised classification has been largely ignored by subsequent researchers [e.g., Xing et al. (2014) considered H. foulkii to be nominum dubium on the basis of a lack of reliable diagnostic characters and, therefore, advocated for the traditional division of the Hadrosauridae into Hadrosaurinae and Lambeosaurinae]. 13

Hadrosaurid remains are ubiquitous within North America’s Late Cretaceous sediments and are known from isolated remains, monotaxic and multitaxic bonebeds

(Rogers 1990; Varricchio and Horner 1993; Varricchio 1995; Colson et al. 2004; Scherzer and Varricchio 2010), ichnofossils (Currie et al. 2003; Rodriguez de la Rosa 2007; Lucas et al. 2011; Bell 2012; Fiorillo et al. 2014), and as components of vertebrate microfossil sites (Eberth and Evans 2011). Hadrosaurs are common components of the dinosaur assemblages in Alberta. In the fossil-rich Belly River Group there are currently eleven species recognized: Brachylophosaurus canadensis Sternberg 1953, Gryposaurus notablis Lambe 1914, G. incurvimanus Parks 1919, Prosaurolophus maximus Brown

1916, Corythosaurus casuarius Brown 1914, C. intermedius Parks 1923, Lambeosaurus clavinitialus Sternberg 1935, L. lambei Parks 1923, L. magnicristatus Sternberg 1935, and

Parasaurolophus walkeri Parks 1922 from the Dinosaur Park Formation, and B. canadensis and Hypacrosaurus stebingeri Horner and Currie 1994 from the Oldman

Formation (Ryan and Russell 2001; Longrich 2008; Eberth and Evans 2011). Undescribed hadrosaurid remains are also known from the Foremost Formation (Ryan and Russell,

2001; personal observation, 2008).

Bonebeds

Bonebeds are fossil assemblages that preserve the remains of multiple individuals, from as few as two individuals to as many as hundreds, and possibly even thousands (Ryan et al. 2001). Bonebeds can form as the result of catastrophic (non- selective) forces or attritional (selective) forces that accumulate remains over time

(Varracchio and Horner 1993; Rogers et al. 2008). Additionally, remains can be 14

preserved at the location of death (autochthonous) or they can be transported

(parautochthonous if near the site of origin or allochthonous if more distal), typically in fluvial settings, to a final location of burial. All bonebeds, regardless of their unique history, can provide important biological and sedimentological data for paleontologists and geologists. Catastrophic mass-death assemblages are the most useful for considering species interactions in extinct animals, as these assemblages are typically interpreted to represent a single, discrete event in time. The taphonomic data from dinosaur bonebeds can be combined with observations made from the dinosaur's living relatives—birds and crocodiles—which are incorporated in analyses made using the phylogenetic inference methodology first proposed by Bryant and Russell (1992), and later popularized by Witmer (1995) as the Extant Phylogenetic Bracket methodology.

Bonebeds were not the primary focus for dinosaur collectors who were charged with finding articulated skeletons and complete skulls for museum displays during the early days of dinosaur paleontology. However, in the first half of the twentieth century some scientists began to recognize that the information contained in the sediments surrounding the fossils could be important to interpreting the postmortem history of the fossil remains and to making inferences about the animal's life history (Efremov

1940). The term “taphonomy” was coined by Efremov (1940) who described it as a discipline that, “stands on the border of paleontology, uniting it both with geology and biology.” Taphonomy studies the processes that act on an organism after it dies and as it transitions to the rock record. During the “Dinosaur Renaissance” (Bakker 1975) of the

1970s, the discipline of taphonomy began to play a greater role in paleontological 15

studies as debates intensified over issues of dinosaur physiology and behavior.

Bonebeds are now recognized as providing a wealth of taphonomic data that can be applied to many different lines of paleontological inquiry, such as gregarious behavior

[e.g., ceratopsids (Ryan et al. 2001); hadrosaurs (Varricchio and Horner 1993)], pack hunting in theropods (Currie 1998), and age-class (cohort) separation in a variety of taxa

(Varricchio and Horner 1993; Varricchio et al. 2008). They have also been used to stimulate conversation regarding sexual dimorphism in dinosaurs (e.g., Lehman 1990,

Saitta 2015). Additionally, monodominant bonebeds (bonebeds dominated by a single taxon; Eberth and Rodgers 2005) can potentially provide excellent insights into ontogeny by preserving a growth series of diagnostic elements (Horner et al. 2000; Ryan et al. 2001).

Described hadrosaur bonebeds include monodominant examples for hadrosaurines (Fiorillo and Gangloff 2001; Colson et al. 2004; Bell and Campione 2014;

Hone et al. 2014; Rogers 1990) and lambeosaurines (Lauters el al. 2008; Varricchio and

Horner 1993; Varricchio 1995; Fiorillo and Gangloff 2001; Colson et al. 2004), as well as multitaxic bonebeds including both hadrosaurine and lambeosaurine remains

(Varricchio and Horner 1993; Scherzer and Varricchio, 2010).

Histology

Histology is the microscopic examination of biological tissues. While the direct study of soft tissues is not available when studying non-avian dinosaurs and other extinct animals [although extraordinary preservation within konservat lagerstatten does provide some evidence of what soft-tissue structures may have looked like, e.g., Bell et al. (2014)], paleontologists can use histological methods on preserved hard tissues, such as bones, tendons, scutes, and teeth. The preparation of histological slides from fossil material closely parallels the preparation of petrographic slides used in geological studies. Histology of fossil material (paleohistology) offers the opportunity to examine dinosaur biology in ways that would not be possible from gross examination alone. Prior to the microscopic renaissance in paleontology, paleontologists relied on examination at the macro level, using morphological techniques and stratigraphic and spatial context to attempt to answer questions regarding dinosaur physiology, growth, and evolution.

While these techniques remain invaluable, they are undeniably limited. Paleohistology gives researchers an extra tool to develop and test the veracity of a wide range of hypotheses.

The microscopic examination of fossil material is not a new concept (e.g.,

Moodie 1917; Wilson 1927; Moodie 1928), however recent technological advances in microscopy have improved both the quality and accessibility of histological analyses.

Over the last several decades there has been a tremendous increase in the body of paleohistological literature (see Erickson 2005). Paleohistology has been used as a tool

to investigate questions regarding taxonomy, growth patterns, population dynamics, endemism, and behavior in a variety of dinosaurs, including sauropods (Sander 2000;

Sander et al. 2006; Cerda and Powell 2010; Klein et al. 2012), theropods (Varricchio

1993; Fowler et al. 2011), ceratopsids (Erickson and Tumanova 2000; Hieronymus et al.

2009; Reizner 2010; Scannella and Horner 2010; Erickson and Druckenmiller 2011), and hadrosaurs (Reid 1985; Horner et al. 1999; Horner et al. 2000; Adams and Organ 2005;

Chinsamy et al. 2012; Vanderven et al. 2014). Histological studies have also examined other archosaurs, including crocodiles (de Buffrenil and Buffetaut 1981), pterosaurs (de

Ricqles et al. 2000; Buffetaut and Mazin 2003; Padian et al. 2004) and Aves (Houde

1987).

Almost any element of the body can be sectioned; however, for studies attempting to quantify and describe growth within taxa, the long bones of the appendicular skeleton are most commonly utilized as they offer several advantages over other elements (Sander 2000). In addition to typically being well-represented in museum collections, long bones almost universally possess a simple geometry—long and straight—that does not undergo radical changes in shape or proportion during growth. This is most true for the region towards the center of the diaphysis, and in some taxa (e.g., sauropods; Sander 2000) this region has the oldest and thickest cortex, therefore, potentially preserving the best record of growth. Among long bones, tibiae have been shown to have the best potential for providing growth information in

hadrosaurs (Horner et al. 1999) as their midshafts are not significantly affected during ontogeny by the development of trochanters and condyles.

A cross section of an idealized hindshaft is composed of multiple regions (Fig.

1A). At the center of the bone is the spongy, porous, cancellous tissue of the medullary cavity which would have contained bone marrow during life. The degree of porosity is a function of both phylogeny and ontogeny. The cancellous tissue forms through significant reworking of the primary bony tissues. The processes that cause these extreme changes obliterate many primary features that are important for studying growth histories and therefore necessitate the use of retrocalculation methods to compensate for lost data (Cooper et al. 2008). The outer surface of the medullary cavity

(endosteum) is lined with a zone of strut-like trabeculae. Moving outwards, the cancellous tissue grades into dense, cortical bone (the compacta). Lines of arrested growth (LAGs) and other growth markers can potentially be deposited in this region. The dense tissue of the compacta can also be very informative in regards to degree of vascularity, bone tissue types (i.e., fibrolamellar bone), tissue organization (i.e., longitudinal, reticular, plexiform, and circumferential; Fig. 1B) and osteocyte lacunae density. The outer bone surface is the periosteum.

Hadrosaurs have been the subject of numerous paleohistological examinations over the past several decades (Reid 1985; Horner et al. 1999; Horner et al. 2000; Adams and Organ 2005; Straight et al. 2009; Klein et al. 2012; Chinsamy et al. 2012; Vanderven et al. 2014). They have provided some of the best data for speculating on dinosaur

behaviors such as herding, migration, and parental care. For example, the hadrosaurine

Maiasaura peeblesourm was one of the first dinosaurs for which nesting behavior with paternal care was suggested (Horner and Makela 1979; Horner 1982; Horner 1989). The first dedicated histological examination of a monodominant hadrosaur (Edmontosaurus) bonebed has only recently been published (Vanderven et al. 2014).

Figure 1. (A), representative cross-section through the midshaft of a hadrosaur tibia, and (B), examples of various organizational patterns of tissue observed in the WBB tibiae. Images in both (A) and (B) are from TMP2008.045.0064.

CHAPTER 2. MATERIALS AND METHODS

Field Methods

Wendy’s Bone Bed (WBB) was discovered by Wendy Sloboda prior to the 2003 field season. The bonebed is located approximately 34 km southwest of the village of

Manyberries, Alberta, on the Pinhorn Provincial Grazing Reserve, south of the Milk River

(12U 509570E; 5440724N, WGS 84 datum, 946 m ASL) (Fig. 2). It is situated on the steep edge of a coulee and has a traceable lateral extent of at least 7.5 meters (Fig. 3). The excavated quarry is sub-rectangular and measures approximately 4.0 x 7.5 meters; however, the bone layer extends beyond these boundaries and can be traced around the corner at the north end of the quarry. Overburden removal took place at the site in

2004 and 2005. Subsequently, sixteen 1-m2 grids were mapped and completely excavated using standard excavation techniques (Ryan et al. 2001) over the course of five field seasons (2006–2010) under permits issued by the Government of Alberta to

Michael Ryan (CMNH) and David Evans (ROM). The quarry was closed in 2010 with an additional twelve 1-m2 grids remaining only partially excavated (this includes grids extending into the back wall of the quarry, and partially eroded grids on the margins of the quarry). All collected specimens were prepared at the CMNH and were deposited in the Collections of the TMP. Data collected in the field included maximum length, orientation (degrees east of north), plunge, and any obvious taphonomic modification characters (abrasion, breakage, tooth marks, and weathering features).

Figure 2. Map of southern Alberta relevant to field area. Approximate location of Wendy’s Bone Bed is marked by yellow star. Inset: map of Canada with yellow star corresponding to approximate location of Wendy’s Bone Bed. Figure after Ryan et al. 2001.

of of

lose

he left of the the photo. he(B), of left

sides. The proximity of the bone bed to the ofthe bed bone The proximity sides.

visible on adjacent hill on adjacent visible

photo showing the bonebed and its position in the lower Oldman lower Oldman the the position in and photobonebed its showing

panoramic

Bone Bed quarry. BedBone

(A), (A),

Wendy's

Figure the Formation and the between Oldman the approximate contact Formation.line traces White underlying Formation Foremost t at visible withmeandering river the Milk visible, River is also the

season. Rose diagram using diagram using Roseseason.

Quarry map for the WBB as of the end of the 2010 field of the 2010 as end the of the WBB Quarry for map

. (A)

Figure4 100 andmm than (C) (B), specimens longer for all specimens mapped orientationdata for all

Definitions of the taphonomic features followed Ryan et al. (2001). The taphonomic modifications were reassessed and corrected, if necessary, after preparation, and prepared specimens were re-measured to confirm total length.

Laboratory Methods

Six tibiae were selected for histological sampling (Table 1). Maximum lengths and other significant parameters (e.g., midshaft circumference) were measured using

Mitutoyo Digimatic Calipers and a metric ruler or measuring tape. Orientation data collected for all of the mapped specimens was plotted in a rose diagram (Fig. 4B). A second plot (Fig. 4C) used only those elements with a maximum length greater than 100 mm (such as complete limb bones), as these elements would be most likely to provide evidence of an orienting current. For the small number of elements that had orientation, but not length, recorded on the field data sheets, length was measured off of the maps.

Archival photos were taken of each tibia from all sides—anterior, posterior, medial, lateral, and proximal and distal ends—using traditional photographic techniques with a Nikon D3100 digital SLR camera. Photogrammetry was used to produce an archival, three-dimensional model for each specimen.

The methodology for producing histological slides is outlined in Appendix A.

Table 1. Tibiae selected for histological sectioning from the WBB, including morphological measurements and summary of histological features.

RTMP number Element Maximum Mid shaft Number Bone tissue Secondary side length circumference of lines types (Haversian) (mm) (mm) of tissue? arrested growth (LAGs)

2008.045.0064 — incomplete 236 1 longitudinal, No reticular, circumferential, radial

2009.038.0008 — incomplete 265 0 reticular, No circumferential

2009.038.0032 left 454 144 0 longitudinal, No reticular, circumferential

2010.078.0012 — 411 152 0 longitudinal, No reticular, circumferential,

2010.078.0014 left 719 237 1 reticular, No circumferential, radial

2010.078.0022 right 492 156 0 reticular, No circumferential

CHAPTER 3. REGIONAL AND LOCAL GEOLOGY

Regional Geology

The Campanian Belly River Group of southern Alberta (formerly recognized in the literature as the Judith River Group) represents an interval of approximately 5.8 million years, ranging from 80.0 Ma to 74.2 Ma (Eberth 2005). The Belly River Group correlates with part of the Two Medicine Formation of Montana which spans a longer period of time (Rogers 1990). The Belly River Group was deposited as an eastward- thinning clastic wedge along the Western Interior Seaway, and shifts from non-marine to coastal sediments. Sediments were deposited in several depositional environments across the region including fluvial, floodplain, estuarine, swamp, and lagoon environments (Eberth and Hamblin 1993). The Belly River Group is divided into three formations; in ascending order these are the Foremost, Oldman, and Dinosaur Park formations (Fig. 5A; Eberth and Hamblin 1993). The Foremost Formation consists primarily of marine rocks and represents a transitional unit between the underlying, fully-marine Pakowki Formation and the non-marine rocks of the overlying Oldman

Formation (Ryan et al. 2012). It is bounded below by the McKay Coal Zone and is capped by the Taber Coal Zone (Ryan et al. 2012). The Oldman Formation conformably overlies the Foremost Formation and is divided into three informal units: a muddy lower unit, a coarse middle unit known as the Comrey sandstone, and a muddy upper unit (Eberth

2005). The lower and upper units are both dominated by fine-grained mudstones and have frequent ironstone concretions and lenses. The Dinosaur Park Formation contains

massive, slightly inclined, sandstone bodies with dense fossiliferous facies. The Dinosaur

Park Formation is overlain by the marine shales of the Bearpaw Formation. Regionally, a diachronous discontinuity defines the unconformity between the Dinosaur Park and

Oldman formations with the contact becoming younger towards the southeast corner of the province (Eberth and Hamblin 1993). As a result, the outcrops of the uppermost unit of the Oldman Formation in the south are time equivalent to the basal portion of the

Dinosaur Park Formation in well-known localities to the north, such as Dinosaur

Provincial Park.

Local Geology

The badlands that form the southern boundary of the Milk River Valley preserve outcrops of the upper Foremost Formation and the complete Oldman Formation.

Exposed sediments in the vicinity of the bonebed are limited to the upper Foremost and lower unit of the Oldman Formation.

The bonebed is located on the east side of a cliff face, approximated 500 m south of the Milk River. In the immediate area of the bonebed, the upper Foremost

Formation and its contact with the Oldman Formation can clearly be seen outcropping on adjacent hills (Fig. 3).

Located approximately four meters below the prairie level, the WBB bone layer is a fissile, but well-consolidated, grey-black mudstone. The bone layer varies in

thickness with a maximum thickness of approximately 50 cm. Small amber and charcoal inclusions are common.

Above the bone layer is a series of stacked fine-grained mudstones and sandstones of the lower Oldman Formation (Fig. 5C). Most contacts between units are gradational, with units being differentiated primarily by changes in sediment color and minor changes in grain size. However, several well-defined contacts between units suggest the possibility that this package of rock represents an overbank deposit resulting from multiple flood events.

Lateral exposure in the immediate area of the bonebed is limited by both vegetation cover as well as by large amounts of recent slope wash, making observations of lateral facies changes unfeasible within the confines of this project.

silhouette highlights bone layer in (B). Regional layer silhouette(B). bone in highlights

, regional stratigraphy in the vicinity of the Milk River Milk of the the invicinity , regional stratigraphy

(A)

Gryposaurus Gryposaurus

(C)

l WBB stratigraphy WBB l

loca

General stratigraphy of southern Alberta General of southern stratigraphy

, and

(B)

Figure5 valley 2005. stratigraphyEberth dates after and

CHAPTER 4. CRANIAL AND POSTCRANIAL ANATOMY

Cranial elements present in the bonebed include multiple dentaries and maxillae, as well as a single example each for the nasal, frontal, lacrimal, and jugal (Fig.

6). These are described below:

Frontal: The frontal has a conservative morphology across the genus. It is broad and has a sigmoidal nasofrontal suture that is diagnostic for the genus. The shape of this anterior suture creates an incised mid-sagittal notch that receives a narrow posterior extension of the nasal. Also characteristic for the genus, a narrow lateral extension of the frontal contributes to the superior portion of the orbit (Fig. 6). TMP2006.050.0001 is a left frontal that preserves the sigmoidal suture, as well as a prominent ridge that runs mediolaterally on the ventral surface.

Nasal: The gryposaur nasal is a hatchet-shaped element that possesses the diagnostic arch or hump, and a long anterior process that articulates with the premaxilla but terminates before reaching the anterior margin of the external nares.

TMP2010.078.0009 is an incomplete left nasal, missing the entire anterior process as well as the posterior margin that articulates with the frontal in a diagnostic sigmoidal suture. Preserved is the apex of the nasal arch as well as a portion of the rugose medial suture.

Jugal: The jugal of Gryposaurus possesses a postorbital process that is close to parallel with the body of the jugal, a large posteroventral flange, and a narrow posterior process. In G. incurivmanus the posteroventral flange possesses a diagnostic spur in

posterior margin. TMP2009.038.0058 is an incomplete right jugal. The anterior process is completely missing and the posterior process and posteroventral flange are significantly damaged. Preparatory reconstruction of the posterior area is questionable and therefore it does not offer a reliable picture of this portion of the element. The postorbital process is present and appears to ascend at approximately 90°, but it is missing its distal portion. A small spur projects off the inferior margin, directly below the midline of the infratemporal fenstra; this is similar to the described jugal of G. incurvimanus. The placement of the observed spur in TMP2006.050.0001 is considerably anterior to the described placement in G. incurvimanus, however.

Dentary: The anterior-most portion of the dentary turns downwards; this condition is exaggerated in G. monumentensis. Dentaries from the WBB are gracile and possess a tall coronoid process. The anterior articular surface for contact with the predentary is dorsally concave (Fig. 7).

Maxilla: Maxillae tend to be robust and triangular in shape, with a tall dorsal process rising from the middle of the element. The shape of the lateroventral margin is variable among species, with G. notablis and G. monumentensis possessing a strongly sigmoidal margin, G. latidens possessing a gently arcuate margin, and G. incurvimanus possessing a generally straight margin. Maxillae recovered from the WBB are robust and triangular, consistent with what has previously been described for the genus.

Lacrimal: The single lacrimal recovered from the WBB is too fragmentary to recover any reliable morphological data.

Appendicular elements and elements of the pelvic girdle are the most common elements of the postcrania in the WBB. This includes multiple femora (n = 10), tibiae (n

= 8), humeri (n = 2), ilia (n = 2), pubes (n = 2), and ischia (n = 3) (Figs. 7, 8). One relatively complete ischium (TMP2009.038.0052) with a complete distal end lacks an expanded boot (Fig. 8E, F ), a character diagnostic of hadrosaurine hadrosaurids (Horner et al.

2004).

A B

Figure 6. Representative illustration of Gryposaurus skull in right lateral (A) and dorsal (B) views. Elements recovered from the WBB are highlighted. Abbreviations: Pd, predentary; D, dentary; Su, surangular; Ar, articular; Pm, premaxilla; Ma, maxilla; Na, nasal; La, lacrimal; J, jugal; Pf, prefrontal; F, frontal; Po, postorbital; Sq, squamosal; Qu, quadrate; Qj, quadratojugal.

Figure 7. Representative dentaries from the WBB, used for determining MNI. (A) TMP2009.038.032; (B) TMP2009.038.0001; (C) TMP2009.038.0017.

A C

B D

10 cm 10 cm

10 cm

Figure 8. Representative pelvic elements from the WBB. Left ilium in (A) medial view and (B) lateral view. Right pubis (TMP2009.038.0072) in (C) lateral view and (D) medial view. Left ischium (TMP2009.038.0052) in (E) medial view and (F) lateral view

Figure 9. Representative appendicular elements from the WBB. Right humerus (TMP2009.038.0049) in (A) lateral view and (B) medial view. (C) radius, medial view; D, radius, lateral view; E, right scapula, dorsal view; F, right scapula, ventral view; G, left femur, lateral view; H, left femur, medial view.

Hadrosaur postcrania, both in hadrosaurines and lambeosaurines, is highly conservative across taxa. Taxonomic distinctions beyond sub-family are largely dependent on cranial material. Diagnostic cranial elements are typically the paired frontals, nasals, and premaxillae. The WBB hadrosaur is identified as the hadrosaurine Gryposaurus based on the distinctive left nasal arch, or hump (TMP2010.078.0009) (Fig. 10), and the sigmoidal nasofrontal suture on the left frontal (TMP2006.050.0001). Identification at the species level is not possible with the material presently available. Additionally, the ischia present in the bonebed have a straight profile which is consistent with other described gryposaurs (Kirtland et al. 2006).

A C

B D

5 cm 10 cm

E F

5 cm

Figure 10. Cranial elements from the Wendy’s Bone Bed. (A) right jugal, medial view; (B) right jugal, lateral view; (C) right maxilla; (D) right maxilla; (E) left nasal, medial view; (F) left nasal, lateral view. Nasal preserves the apex of the characteristic gryposaur nasal arch. The rugose surface of the medial suture is visible in (E).

The six tibiae selected for histological sectioning are described briefly below:

TMP2008.045.0064 (Fig. 11) is an incomplete tibia (maximum length of 521 mm; midshaft circumference of 236 mm) with significant bone loss proximally and significant distortion distally. Due to this damage, the specimen cannot be assigned as a right or left side element. Despite the damage to the epiphyseal regions, the diaphysis is well preserved with little taphonomic compression. TMP2009.038.0008 (Fig. 12) is an incomplete tibia (maximum length of 482 mm; midshaft circumference of 265 mm) with significant taphonomic bone loss both proximally and distally. Due to this damage, the specimen cannot be assigned as a right or left side element. TMP2010.078.0014 (Fig. 13) is a left tibia (719 mm in length, midshaft circumference of 237 mm), and is the largest tibia recovered from the bonebed. TMP2009.038.0032 (Fig. 14) is a complete left tibia

(454 mm in length; midshaft circumference of 144 mm) with significant taphonomic distortion. TMP2010.078.0022 (Fig. 15) is a complete right tibia (492 mm in length; midshaft circumference of 156 mm). TMP2010.078.0012 (Fig. 16) is an incomplete tibia

(maximum length of 411 mm; midshaft circumference of 152 mm) with taphonomic loss of bone both proximally and distally.

Figure 11. TMP 2008.045.0064, an incomplete tibia, viewed in (A) gross view, and (B) transverse cross section. Arrow corresponds to plane of section.

Figure 12. TMP 2009.038.0008, an incomplete tibia, viewed in (A) gross view, and (B) transverse cross section. Arrow corresponds to plane of section.

Figure 13. TMP 2010.078.0014, a complete left tibia, viewed in (A) gross view, and (B) transverse cross section. Arrow corresponds to plane of section.

Figure 14. TMP 2009.038.0032, a complete left tibia, viewed in (A) gross view, and (B) transverse cross section. Arrow corresponds to plane of section.

Figure 15. TMP 2010.078.0022, a complete right tibia, viewed in (A) gross view, and (B) transverse cross section. Arrow corresponds to plane of section.

Figure 16. TMP 2010.078.0012, an incomplete tibia, viewed in (A) gross view, and (B) transverse cross section. Arrow corresponds to plane of section.

CHAPTER 5. TAPHONOMY

Taxonomic Composition of Wendy’s Bone Bed

Over 96% of the collected material is assignable to Hadrosauridae with diagnostic cranial elements (TMP2006.050.0001, a left frontal; TMP2010.78.0009, a partial left nasal) diagnostic for Gryposaurus. Shed theropod teeth are present in the bonebed but are rare (n = 2). A ceratopsid ilium and a Stegoceras supraorbital are the only other identifiable ornithischian elements. There are a small number of fragments that cannot be reliably assigned beyond Dinosauria; these are the heavily abraded bone chips that are ubiquitous in bonebed deposits (Ryan et al. 2001). The minimum number of individuals (MNI) is three, based on complete or near-complete dentaries (Fig. 7;

TMP2009.038.0017, TMP2009.038.0032, TMP2009.038.0001; one right and two left, respectively). The right dentary is considerably larger than both left-side dentaries and can therefore be reliably assigned to a unique individual. Additionally, two pairs of associated right and left femora that may represent two individuals were identified, along with a similar but significantly larger pair of tibiae, thus supporting the MNI of three.

Taphonomic Modifications

Prior to fossilization, animal carcasses can be affected by a variety of modifying forces. Bioturbation (scavenging by predators, trampling, etc.), fluvial transport, and prolonged subaerial exposure can all significantly modify bones. The lithostatic pressure

of overlying sediment loads can also deform freshly buried bones. Fossilized bones can also be affected by modern weathering forces (i.e. erosion at the surface) and can be damaged during collection efforts.

Elements were assessed for a variety of taphonomic modifications, including breakage, fractures, abrasion, and weathering, following the protocol outlined by Ryan et al. (2001).

Most WBB elements are incomplete or are minimally missing some small chips of bone (Fig. 17). Depending on their degree of completeness, elements were assigned to one of four breakage classes: Class 0, no breakage; Class 1, a break on the proximal end of the element; Class 2, a break on the distal end of the element; Class 3, breaks on both the proximal and distal ends of the element.

Over 68% (n = 72) of the WBB material exhibit Stage 3 breakage; 15% (n = 16) showed either Stage 1 or Stage 2 breakage, and 17% (n = 18) showed no breakage

(Table 2).

Observed fractures (Table 2) were assigned to one of five categories, with most elements possessing multiple types of fractures (Fig. 18). Compression fractures can be caused by bioturbating forces or by lithostatic pressure during sediment deposition and diagenesis. Compression fractures often manifest themselves as a series of parallel or sub-parallel cracks. Transverse fractures are those compression fractures that appear perpendicular to the long axis of an element. Longitudinal fractures occur parallel to the

long axis of a bone. Longitudinal fractures are typically associated with desiccation cracking, an effect of weathering; however, in the WBB longitudinal fractures typically do not manifest as shallow cracking or flaking of the periosteal bone, but instead tend to be deep crevices and are interpreted to be the result of compression. Spiral fractures are those fractures occurring on long bones or robust longitudinal portions of elements that show a smooth fracture surface occurring at an oblique angle to the long axis of the element. These fractures have been interpreted to represent “green” fractures in unweathered material and are typically attributed to trampling (Ryan et al. 2001).

Collection fractures are those fractures that occurred recently, during the collection or subsequent preparation of the element. Indeterminate fractures are any fractures that cannot be reliably placed in any of the aforementioned categories. In the bonebed, many of the complete long bones possess a conchoidal fracture pattern adjacent to one or both of the metaphyses. These fractures have a thumbprint-like appearance, with the multiple ridges being pressed progressively deeper in the element. While almost certainly an artifact of compression, the exact mechanism of formation of these fractures is unknown and therefore these fractures are recorded as indeterminate.

The bonebed material is highly fractured (Table 2). Over 99% of the elements showed at least one form of fracture; small fragments (i.e., rib or fragmentary limb elements) that had no fractures on the preserved bone itself, but whose margins were clearly fracture surfaces were recorded accordingly. Compression fractures were the most common and were documented on over 83% of the material (Table 2), with

transverse and longitudinal fractures on all long bones. Half of the material (50%, n = 53) had both transverse and longitudinal compression fractures. Indeterminate fractures, most of which are likely some form of compression fracture, were documented on 39%

(n = 45) of the specimens. Some flat elements have a sub-radial, indeterminate fracture pattern that could be the result of impact with entrained elements during a period of submersion. Spiral fractures or putative spiral fracture were present, but not overly abundant, occurring on 13% (n = 15) of the specimens. Collection fractures were infrequent and were documented on less than 2% (n= 2) of the specimens.

Fiorillo (1988) applied sedimentological concepts to fossil material when he observed that some fossils are rounded and polished during fluvial transport in similar fashion to how sediment grains are rounded by various transport processes. Elements were assigned to one of four distinct abrasion classes: Stage 0, no abrasion; Stage 1, some rounding of the margins; Stage 2, extremities are well-rounded and the bone surface shows some polishing but original bone texture is still present; Stage 3, severe rounding and the original bone texture is almost completely erased from the bone surface.

The vast majority of elements show either no abrasion (55%; n = 59) or very light abrasion assignable to Stage 1 (26%; n = 28). A minority of specimens show Stage 2 abrasion (15%; n = 16) and a minimal number (4%; n = 4) show Stage 3 abrasion. Some elements shows more than one stage of abrasion on different parts of the element (Fig.

19). In these cases the assigned stage was determined based on the dominant stage

present on the element. A pattern of differential abrasion is observed consistently on complete limb bones and is discussed further in Discussion.

Table 2. Summary of abrasion, weathering, fracture, and breakage data. Note: some elements contribute to the counts for multiple fracture modes since a single specimen could display more than one type of fracture.

Modification Stage or Representation class

Abrasion 0 No abrasion 55% (n = 59)

1 Some rounding of edges 26% (n =28)

2 Well-rounded extremities, 15% (n = 16) polishing of bone surface 3 4 % (n = 4) Extreme rounding and loss of

bone texture

Weathering 0 No cracking or flaking of bone 96% (n = 103) surface 1 3% (n = 3) Minor superficial flaking and 2 1% (n =1) erosion of ends 3 0% (n = 0) Deep cracks and significant erosion of ends Extreme flaking and cracking, ends eroded away

Fracturing* T Transverse compression n = 93

L Longitudinal compression n = 54

S Spiral n = 15

C Collection n = 2

I Indeterminate n = 45

Breakage 0 No breakage 17 % (N = 18)

1 Proximal 10% (N = 11)

2 Distal 5% (N = 5)

3 Proximal and distal 68% (N = 72)

Prolonged subaerial exposure can cause significant decomposition of bones.

Behrensmeyer (1978) studied modern mammal carcasses in Amboseli National Park,

Kenya, and was able to define a progression of six distinct weathering classes related to length of time a carcass exposed was exposed typically on an open plain. Most dinosaur material is recovered from fluvial deposits, indicating that the weathering class that an elements is assigned to is indicative of the time of exposure before entrainment in a fluvial system, since the weathering (sensu Behrensmeyer 1978) cannot happen in an aqueous environment (although decay and decomposition can). A modified, four-stage system, has been adapted for dinosaurian taphonomic studies (Fiorillo 1988; Ryan et al.

2001): Stage 0, bone surface shows no signs of cracking or flaking; Stage 1, surface shows some cracking and possibly some erosion to the ends of the elements; Stage 2, deeper cracks and more extreme erosion, with matrix infilling the incomplete ends of the element; Stage 3, extreme flaking of bone and the ends of the element are completely eroded away.

The bonebed material shows very little evidence of weathering, with less than

4% (n = 4) of the material showing any signs of weathering. Three specimens are assigned Stage 1 weathering and one specimen is assigned Stage 2 weathering (Table 2).

Relative Age Profile of Wendy’s Bone Bed

Each catalogued element was assigned into one of three age classes (juvenile, sub-adult, or adult) based on absolute size following the work of Horner et al. (2000) on the hadrosaurine Maiasaura peeblesorum. Complete femora are all of similar size (499– 54

560 mm). Most complete tibiae also fall into a limited size range (411–492 mm), with the exception of one significant large specimen (TMP2010.078.0014; 719 mm). Using limb size as an age-class indicator after Horner et al. (2000), these individuals can be assigned as juveniles (“late juveniles” in Horner et al. 2000). All other identifiable cranial and postcranial elements are consistent with late juvenile size except for one proximal femur whose projected complete length would likely place it as a sub-adult

(TMP2009.038.0050).

Any specimen with observable bone texture was noted. Discrete textures present on certain skull and axial elements have been demonstrated to be reliable indicators of age class in centrosaurine ceratopsids (Sampson et al. 1997; Tumarkin-

Deratzian, 2003; Brown et al. 2009; Tumarkin-Deratzian, 2010). Long-grain texture is indicative of juvenile status, mottled texture is indicative of sub-adult status, and rugose texture is indicative of adult status. The later-stage textures (mottled and rugose) do not appear suddenly with complete obliteration of the previous texture; instead, the new texture progresses and gradually replaces the earlier-stage texture as the animal continues along its ontogenetic trajectory. This results in individuals that are intermediate between juvenile and sub-adult textural endpoints that have a discrete boundary separating a region of juvenile long-grain texture from a region of encroaching mottled texture on the same element. The same transition can be observed between the mottled sub-adult texture and the rugose adult texture. These textures have been observed on the parietals and squamosals of the ceratopsid skull, and on the ilia. While

this same phenomenon has not yet been tested in hadrosaurs, this information may prove useful to future investigations and is discussed further in Discussion.

Figure 17. A tibia (TMP2008.045.0064) demonstrating Class 1 breakage (proximal breakage)

Figure 18. A femur showing examples of both transverse and longitudinal compression fractures.

Figure 19. An ilium with areas of both Stage 1 and Stage 2 abrasion.

CHAPTER 6. HISTOLOGICAL DESCRIPTIONS

TMP2008.045.0064 (Fig. 20A). The medullary cavity appears well-developed; however, free-floating fragments of trabecular bone (likely resulting from damage during diagenesis) that are visible in the Castolite resin suggest that a more elaborate zone of trabeculae was likely in place during life. Longitudinal primary tissue that lines the medullary cavity has been mostly resorbed to form the zone of trabecular bone, although some is still visible interstitially. Progressing towards the periosteum, the longitudinal tissue grades into a zone of reticular fibrolamellar bone. The reticular bone tissue then grades into a zone of circumferential fibrolamellar that continues periosteally until stopping abruptly at a LAG that completely circumscribes the cortex.

Reticular fibrolamellar bone resumes immediately outside of the LAG. The reticular tissue along the periosteal margin of the growth mark is notably more vascularized than the circumferential tissue on the endosteal margin. The reticular tissue continues periosteally until grading into circumferential tissue which then terminates at the periosteum with no external fundamental system. An area towards the anterior of the section, spanning radially from the endosteal surface of the medullary cavity all the way to the periosteum, appears to be radially oriented fibrolamellar bone. It is notable in that it only occurs in one small area of the slide and it obscures the otherwise clear LAG, suggesting that it might be secondary tissue. When examined under cross-polarized light, however, there are no birefringent cement lines that would indicate the presence of secondary osteons (Haversian systems).

TMP2009.038.0008 (Fig. 20B). The bone tissue is very dark in section and appears to be dense endosteally, with a thick zone of trabecular bone and a small, incipient medullary cavity containing many small and large erosion rooms. Small, isolated, erosion rooms extend into the compacta; however, no secondary osteons are present. The bone tissue has considerable circumferential variability, with reticular fibrolamellar bone and circumferential fibrolamellar bone alternating around the section. The clearest and most informative radial transect displays tissues that uniformly grade into each other. Progressing outward, these are the trabecular tissue, a dense zone of reticular fibrolamellar bone, a thin zone of circumferential fibrolamellar bone, a thin zone of reticular tissue, and a thin zone of circumferential tissue that terminates at the periosteum. Lateral to this transect, the tissue is more variable, with only two thick zones visible outside of the trabecular bone: a dense zone of reticular fibrolamellar bone that is succeeded by a dense zone of circumferential fibrolamellar bone; there is no external fundamental system visible.

On this slide the lateral transition from reticular to circumferential organization can be observed clearly in several areas of the compacta. Several areas of the cortex appear to show a putative LAG; however, in none of these instances can this feature be traced continuously around the available compacta and, therefore, it should not be counted as LAG.

TMP2010.078.0014 (Fig. 20C). The medullary cavity is lined by a narrow trabecular zone which grades periosteally into a zone of reticular fibrolamellar bone

followed by a zone of circumferential fibrolamellar bone before stopping abruptly at a

LAG. The LAG circumscribes the entire shaft, but the transition from reticular to circumferential organization is not uniform around the section, and the LAG is not as clearly defined as in TMP2008.045.0064. Reticular tissue resumes on the periosteal margin of the LAG and continues, in some areas of the section, to the periosteum; however, in most areas the reticular tissue grades into circumferential tissue which then continues until reaching the periosteum, terminating with no external fundamental system. Similar to TMP2008.045.0064, there is an isolated region—albeit smaller in this slide—where there appears to be radial fibrolamellar bone extending from the endosteal margin to the periosteal surface.

Figure 20. Representative sections of three WBB late juvenile tibiae. (A) TMP2008.045.0064; (B) TMP2009.038.0008; (C) TMP2010.078.0014. Rectangles along the right margin correspond to identifiable zones of circumferential fibrolamellar bone (C) and reticular fibrolamellar bone (R). White arrowheads indicate a LAG. Periosteal surface is up.

TMP2010.078.0022 (Fig. 21A). Significant taphonomic distortion and loss of trabecular bone is observed within the medullary cavity. Virtually no trabecular tissue remains in section; however, several trabeculae still in situ suggest that a thin zone of trabecular tissue once lined the medullary cavity. Proximal to the trabeculae is a region of dense reticular fibrolamellar bone that grades into a thin zone of circumferential fibrolamellar bone near the periosteum. The reticular fibrolamellar bone can be subdivided into a less-vascularized inner (endosteal) region and a more-vascularized outer (periosteal) region. No external fundamental system is present.

TMP2009.038.0032 (Fig. 21B). Taphonomic displacement of material caused by large fractures has collapsed a portion of the outer cortex into the more porous spongy bone, resulting in the medullary cavity appearing smaller than it likely was in life. A large zone of trabecular bone has formed at the center of the section and large erosion rooms extend beyond the cancellous bone, and well into the compacta. The trabecular tissue grades into a dense zone of longitudinal bone tissue, with many primary osteons clearly visible under plane polarized light. Progressing periosteally, the longitudinal bone abruptly transitions to a zone of highly-vascularized reticular fibrolamellar bone that grades into a zone of dense, relatively poorly-vascularized reticular fibrolamellar bone.

In some areas of the slide, this dense reticular tissue continues all the way to the periosteum. In other areas, the reticular tissue grades into a thin zone of circumferential fibrolamellar bone before reaching the periosteum. No external fundamental system is present. The vascularity and nature of the reticular tissue is variable, both radially and

circumferentially. In some areas near the periosteum there is a clear, abrupt, lateral transition from reticular to circumferential tissue organization.

TMP2010.078.0012 (Fig. 21C). The medullary cavity appears to be insipient with very little bone resorption having occurred at the time of death. Cortical tissue appears to be highly vascularized, although this appearance is not uniform around the bone.

Beyond a relatively dense trabecular zone, there is a large, highly vascularized zone of longitudinal bone that grades into a thin zone of highly vascularized reticular fibrolamellar bone, which in turn grades into a thin zone of highly-vascularized circumferential fibrolamellar bone that terminates at the periosteum. It appears that there may be at least one poorly defined LAG, although circumferential cracks in the compacta make it difficult to reliably identify LAGs, as they could potentially provide a plane of weakness that could result in preferential fracturing during diagenesis.

Figure 21. Representative sections of three WBB early juvenile tibiae. (A) TMP2010.078.0022; (B) TMP2009.038.0032; (C) TMP2010.078.0012. Rectangles along the right margin correspond to identifiable zones of circumferential fibrolamellar bone (C) and reticular fibrolamellar bone (R). Periosteal surface is up.

CHAPTER 7. DISCUSSION

Anatomical evidence indicates that the WBB hadrosaurid can be referred to

Gryposaurus sp., a hadrosaurine that lived in the western interior of North America during the Late Cretaceous. Four species of Gryposaurus have been described: G. notablis Lambe, 1914; G. incurvimanus Parks 1919; G. latidens Horner 1992; and G. monumentensis Gates and Sampson 2007. The genus is one of the most widely distributed hadrosaurines, both geographically and temporally, ranging from Alberta to

Utah, and stratigraphically spanning over five million years (Gates and Sampson, 2007;

Sampson, 2012). Gryposaurus is distinguished by a relatively deep skull (Gates and

Sampson, 2007) and a prominent nasal arch or “Roman nose” (Fig. 6) (Gates and

Sampson, 2007; Bell and Evans, 2010; Eberth and Evans, 2011) from which the name

Gryposaurus (“hook-nosed lizard”) is derived.

The WBB gryposaur is diagnosed as Gryposaurus sp. based on cranial material that is diagnostic for the genus (described in detail in Anatomy). Diagnosis at the species level depends largely on the presence of articulated elements of the cranium—namely the nasal, jugal, lacrimal, postorbital, frontal, and squamosal—which are absent from the WBB altogether (i.e., postorbital, squamosal) or are too incomplete to use for meaningful taxanomic comparison (i.e. nasal, lacrimal). The nasal can be diagnostic at the species level, specifically with regards to the level of the nasal arch relative to the frontal plane (above the frontal plane in G. notablis, G. latidens, and G. monumentensis; below the frontal plant in G. incurvimanus) and placement relative to the orbits. While

the apex of the diagnostic gryposaur nasal arch is present on TMP2010.078.0009, the inability to assess this element relative to the skull roof and orbits limits its diagnostic functionality. The frontal (TMP2006.050.0001) preserves the sigmoidal nasofrontal suture that is diagnostic of the genus, but its taxonomic usefulness is limited as it is not associated with the nasal or other skull elements. The observed bony spur on the posterior margin of the jugal (TMP2009.038.0058) and its similarity to the described condition of G. latidens is the only potentially diagnostic morphological comparison that can be made between the WBB cranial material and previously described gryposaur cranial material (however they are not identical; see Anatomy).

When placed in a stratigraphical context the four species of Gryposaurus cluster into two discrete temporal zones. A late Campanian zone includes G. notablis and G. incurvimanus from the Dinosaur Park Formation of southern Alberta as well as G. monumentensis from the Kaiparowits Formation of Utah. An early late-Campanian zone contains G. latidens in northern Montana [the “Gryposaurus latidens Biozone”, Horner et al. (2001)]. The WBB gryposaur, located in the lower unit of the Oldman Formation, falls between these two faunal zones, and therefore either extends the stratigraphic range of a currently recognized species or it represents a new species all together.

Taphonomy

Based on the taphonomic data, and the monodominant make-up of the bonebed, the WBB can be described as a parautochthonous mass death assemblage, representing a biological accumulation of individuals and not a geological accumulation 68

(i.e., lag deposit). Some hydraulic reworking of the bonebed either through transport, winnowing, or both, is suggested by the disarticulated nature of the bonebed and the preferential preservation of robust elements. However, the association of certain elements, such as the femur and tibia of the hind limb (Fig. 4), throughout the bonebed suggests that the hydraulic forces that modified the bonebed were either low-energy or brief in duration. The rose diagrams generated from orientation data (Fig. 4B, C) indicate a lack of preferential orientation in the bonebed, which further supports the interpretation of the hydraulic forces acting on the carcasses as being low-energy and brief.

The taphonomic signature of the collected WBB elements is relatively consistent throughout the entire sample. The bonebed material is significantly broken and fractured, but minimally abraded and minimally weathered. Many elements show one or more forms of compression-induced fracturing. Femora tend to be missing part of, if not the entire, apex of the fourth trochanter. Tibiae tend to have little remaining of the proximal condyles. All limb bones show considerable anteroposterior or mediolateral compression, however in some specimens this compression is limited to the epiphyseal regions and the mid shaft is minimally affected (e.g., tibiae specimens

TMP2008.045.0064 and TMP2010.078.0014). The nature of this compression—uniform along a single bone and uniform across elements in the bonebed—suggests that it is the result of lithostatic compression. The magnitude of compression-related deformation is consistent with the very-fine nature of the sediments of the bone lithosome. Fossils

preserved in coarser sediments tend to show less compression-related deformation

(Ryan et al. 2001).

Elements with a dominant long axis have a series of sub-parallel transverse fractures that commonly penetrate all the way through the bone. In some cases, such as on the coronoid processes of dentaries, there are parallel sequences of spiral fractures.

Transverse fractures are also common at the base of the robust distal condyles of the femora and tibiae. Limb bones frequently exhibit a pattern of concentric, crescent- shaped conchoidal fractures at one metaphysis, although typically not at both metaphyses. Limb bones also commonly exhibit a condition where the shafts exhibit little to no abrasion (Stage 0 or Stage 1) while the epiphyses show significant abrasion effects: eroded condyles, missing surficial bone texture, and relatively poor consolidation. Scherzer and Varricchio (2010) noted similar features on lambeosaurine limb bones from the Sun River Bonebed in the Two Medicine Formation of Montana.

They attributed this to wet rot of the epiphyses resulting from the bones being partially submerged in standing water, a scenario that might be consistent with the interpretation of the WBB gryposaurs being buried on a floodplain. Alternatively, the observed abrasion pattern may be explained by the ontogenetic stage of the individuals in the bonebed; juvenile animals would have had soft, cartilaginous growth plates at the ephiphyses of their still-growing long bones. The cartilaginous epiphyses could have been more prone to abrasion from entrained sediment relative to the ossified diaphysis,

and under certain fluvial conditions this could potentially result in differential abrasion at the diaphysis and epiphyses.

All collected fossils were disarticulated and tended to be dissociated, with the exception of some possibly associated hind limbs. There does not seem to be preferential preservation from either side of the body, however there is preferential preservation of the hind limb (femora, n = 10; tibiae, n = 8; fibula, n = 0) elements relative to the forelimb (humeri, n = 2; radii, n = 2; ulnae, n = 0). There is an overrepresentation of large, dense, robust elements, such as limb bones, pelvic bones, dentaries, and maxillae. There is an underrepresentation and almost complete absence of smaller, lighter elements, such as vertebral centra and processes, bones of the manus and pes, and flat skull bones (Fig. 22).The underrepresentation of forelimb elements may be due to the glenohumeral joint being more susceptible to disarticulation and subsequent transport relative to the more robust attachments of the hind limbs in the acetabulum of the pelvis.

Evidence suggesting that burial occurred relatively shortly after cessation of hydraulic reworking includes a lack of obvious trample or bite marks or invertebrate borings on the bones. The lack of bite marks, along with the presence of only two shed theropod teeth (one assignable to Tyrannosauridae, most likely the large tyrannosaurid

Daspletosaurus; the other assignable to Dromaeosauridae, possibly Saurornitholestes) indicates that the WBB gryposaurs were not extensively scavenged by predators. The

relatively high occurrence of spiral fractures (13%) is enigmatic, as these fractures have typically been attributed to trampling (Haynes 1983).

Figure 22. Diagram showing relative abundance of Gryposaurus skeletal elements in the WBB. Dark colors represent high representation and light colors represent low representation. Gryposaurus skeletal diagram is used with permission by Scott Hartman (2013).

The small number of specimens showing extreme taphonomic effects (those specimens with significant abrasion and identifiable weathering effects) are likely allochthonous elements that were hydraulically introduced to the assemblage or they may have already been present at the final site of burial. In addition to the taphonomic outliers there are also a small number of taxonomic outliers and age-class outliers. A single pachycephalosaurid supraorbital present in the bonebed (TMP2009.038.0054) can be identified as Stegoceras sp. (David Evans, personal communication, 2014). Also present is a single ceratopsid ilium (TMP2008.045.0046). Ceratopsid post crania is conservative across taxa and an isolated ilium does not typically offer robust diagnostic data, however a single ceratopsid, the basal centrosaurine Albertaceratops nesmoi Ryan

2007, is known from the lower unit of the Oldman Formation and the isolated ilium may belong to this taxon. Complete elements that can be assigned to a size-based age-class tend fall into a larger (late) juvenile group and a smaller (early) juvenile group, consistent with the histological data collected from the six sectioned tibiae. There are, however, several fragmentary elements of adult size, including a proximal femur

(TMP2009.038.0050) that would likely scale to an adult size of just over one meter in length. These likely have a similar history to the elements with extreme taphonomic modifications, and were likely introduced to the bonebed in a separate event.

Due to the parautochthonous nature of the assemblage, the mechanism of death is equivocal. Drought has often been attributed as the mode of death for some similar bonebed deposits in the western interior (Rogers 1990; Varricchio and Horner

1993; Gates 2005); however, there is no direct evidence to confirm or reject a drought- induced death for the WBB gryposaurs. Predation is another possibility, however, the underrepresentation of theropod teeth and the lack of bite traces on any elements suggests that this was unlikely. Regardless of the mechanism of death, it appears that the animals died and underwent decomposition on the flood plain. The material was then re-entrained in a subsequent flooding event and transported elsewhere—likely to a final burial place close to the place of death—and light elements of the body were removed at this time.

Histology

The sectioned tibiae all show highly-vascularized, metabolically-demanding fibrolamellar bone, consistent with what has been identified in other dinosaur taxa

(Chinsamy, 2005; Padian and Lamm, 2013). In smaller specimens (early juveniles;

TMP2009.038.0032; TMP2010.078.0012; TMP2010.078.0022; Fig. 21), the innermost cortex is composed of primary osteons arranged longitudinally with erosion rooms indicating the onset of medullary resorption. The longitudinal tissue grades into a zone of reticular tissue, periosteally. Circumferential tissue is observed only as a thin zone just before the periosteum in all of the early juveniles. In the larger late juveniles

(TMP2008.045.0064; TMP2009.038.0008; TMP2010.078.0014; Fig. 20), where resorption has already resulted in a true medullary cavity with struts of trabecular bone lining the endosteal margin, longitudinal tissue can still be identified on individual trabeculae. These specimens show alternating zones of reticular tissue and

circumferential tissue with each reticular-circumferential couplet separated by a LAG

(except TMP2009.038.0008 where taphonomic loss of bone prevents reliable identification of a LAG).

The histological evidence supports the size-based age assignments of the WBB gryposaurs as juveniles, aged less than two years. There are several lines of evidence that support this conclusion. The lack of an external fundamental system—a series of finely spaced growth marks stacked upon one another at the outermost cortex (Horner et al. 1999; Horner et al. 2000)—provides strong evidence that these animals were still growing rapidly, and that they had not yet reached the growth asymptote that would correspond with somatic maturity. As noted by Horner et al. (1999; 2000) the external fundamental system is a key histological marker of an adult individual signifying a rapid deceleration in the rate of bone apposition late in ontogeny. Its presence can be taken to imply the adult status of an individual. The limited development of the medullary cavity, as well as the lack of any secondary osteons, point to all of the sampled individuals as being juveniles. Previous histological examinations of ornithischians, including hadrosaurs, have demonstrated that secondary osteons and even dense

Haversian tissue (zones of dense, overlapping secondary osteons that completely obliterate any primary tissue) are not uncommon is older individuals.

The histological evidence also supports the designation of the WBB gryposaurs as a mixed group of early and late juveniles. Observed differences in the number of

LAGs (one LAG in the largest specimens; no LAGs in smaller specimens) and number of

alternating zones of reticular and circumferential tissue (two reticular-circumferential couplets in larger specimens; one couplet in smaller specimens) between the largest and smallest specimens, indicate that the WBB represents a mixed group of early (less than one year) and late (approaching the end of their second year) juveniles.

Histological Age Profile

The maximum of one LAG in any single specimen prevents using retrocalculation methods to compensate for LAGs lost to remodeling, as doing so would effectively result in attempting to fit a curve to a single data point. Additionally, creating a composite histological profile from an ontogenetic series of WBB elements would have also have been ineffective as only the largest specimens displayed a LAG. As a result, rates of bone apposition and minimum and maximum LAG-based age profiles cannot be quantitatively determined for the WBB gryposaurs. Instead, qualitative data is used to assess relative rates of growth and to assign ages at time of death.

For smaller specimens that show limited medullary resorption and no LAGs, it can be inferred that death occurred before the end of their first year. In these specimens, transitions from reticular to circumferential tissue are typically represented by a single inflection point; that is, only one zone of each tissue type is present in the specimen. This contrasts with larger, LAG-bearing specimens, which show discrete pairings of reticular and circumferential tissue zones, with each pair separated by a LAG.

Larger specimens that show a single LAG and more extensive medullary resorption are interpreted to have died near the end of their second annual depositional cycle. The possibility of a LAG (and therefore the record of a year of growth) being completely obliterated by medullary reconstruction is ruled out due to comparison with the smaller ontogenetic representatives of the bonebed that show no LAGs and no secondary bone deposition.

Previous studies of hadrosaur growth patterns (Horner et al. 1999; 2000;

Vanderven et al. 2014) have found that they experienced a period of sustained rapid growth during early ontogeny and that growth slowed as the individual approached somatic maturity, with a precipitous decrease in apposition rate near the end of ontogeny that is expressed by the presence of the external fundamental system. While specific rates of growth cannot be calibrated for the WBB gryposaurs, the histological evidence strongly supports previous assertions of rapid growth in hadrosaurs. In their study of growth across a growth series of Maiasaura peeblesorum, Horner et al. (2000) determined that juveniles could reach a head-to-tail length of 3.5 meters within their first year. Based on long bone measurements, the WBB gryposaurs represented by the smallest tibiae that were histologically sampled would likely also have been able to hit this same growth milestone. As evidenced by the largest WBB tibiae

(TMP2008.045.0064; 719 mm), this rapid growth was sustained into the second year, during which the WBB gryposaurs could reach approximately 70% of adult size. Studies of predator-prey dynamics in dinosaur communities have proposed that certain prey

species evolved rapid growth regimes as a defense mechanism in an effort to effectively outpace the growth of their primary antagonists. Cooper et al. (2008) demonstrated that the hadrosaurine Hypacrosaurus stebingeri grew at a rate that far exceeded that of the theropods that would have provided the greatest risk of predation. These fast growth rates, combined with gregarious behavior, may have provided hadrosaurs with an effective means of limiting predation.

Chinsamy et al. (2012) conducted a comparative histological study of the hadrosaurine Edmontosaurus from higher latitudes (“polar”) with those from lower latitudes (“temperate”). Their results showed that the polar population had a more consistent histological profile, one defined by discrete alternating zones of reticular fibrolamellar bone and circumferential fibrolamellar bone. The temperate population showed significant histo-variability, with irregular textural switches from reticular to circumferential tissue. None of their sampled specimens from either population had any identifiable LAGs. They attributed the population-wide zonation of tissue types in the polar specimens to be histological signal of overwintering behavior, where harsh environmental effects could cause a predictable decrease in the quality of forage on an annual basis. The more-variable histology of the temperate population was interpreted as representing a population that did not have to endure regular, harsh environmental cycles, but that instead may have had to adapt to temporary and unpredictable environmental perturbations.

Vanderven et al. (2014) conducted a multi-element histological analysis of the

Edmontosaurus Danek Bonebed from the more-temperate Horseshoe Canyon

Formation of Alberta. Sections of femora showed poorly-defined transitions from reticular fibrolamellar bone to circumferential fibrolamellar bone, consistent with the published descriptions of Chinsamy et al. (2012) for temperate Edmontosaurus. This led the authors to advocate for the validity of the overwintering signal described by

Chinsamy et al. (2012) in higher-latitude Edmontosaurus.

Somewhat enigmatically, the WBB gryposaurs show similarities with the published histological profiles of both polar and temperate Edmontosaurus. Specifically, late juveniles from the WBB show consistent zonation of reticular and circumferential fibrolamellar bone, and strongly resemble the polar Edmontosaurus in section. Early juveniles show more histo-variability, with circumferential fibrolamellar bone occurring in more irregular bands. The early juveniles overall bear a stronger resemblance in section with temperate Edmontosaurus. While Chinsamy et al. (2012) do not discuss their results in an ontogenetic context, they do recognize that a histological pattern similar to their overwintering signal had been previously reported by Horner et al.

(1999) in temperate examples of the hadrosaurine Hypacrosaurus. Chinsamy et al. 2012 do not attempt to reconcile this apparent conflict, and instead suggest that temperate

Hypacrosaurus must have endured an annual lack in quality forage much like polar

Edmontosaurus, although they propose no possible catalyst.

Bone texture as a possible indicator of ontogenetic stage

Given the putative ages determined for the WBB gryposaurs (< 2 years old), it is not surprising that the elements do not exhibit the rugose or adult textural patterning reported for ceratopsians that can be used to determine a relative age of sub-adult and adult, respectively. However, some elements do exhibit one of two different forms of long-grain texture that may be relatable to their juvenile status. In all of these instances, the texture is defined by long, parallel grooves that run parallel to the long axis of the element. On some elements these grooves are very shallow and low-relief (such as on ribs) while on other elements the grooves are relatively deep and high-relief (such as on the medial surface of ischia). If this long grain texture can be verified on other putatively juvenile hadrosaurids, then the textural age determination established for ceratopsians may also have utility for hadrosaurids.

Sociality

Previously published studies address the possibility of juvenile sociality in a variety of saurischian and ornithischian dinosaur taxa. It has been proposed that some ornithischian juveniles may have congregated together away from the rest of the population during the season when adults would be preoccupied with rearing altricial hatchlings (Varricchio and Horner 1993). Varricchio et al. (2008) reported a group of over 20 individuals of the ornithomimid Sinornithomimus dongi in the Cretaceous

Djadokhta Formation of Inner Mongolia who all died while mired in the sediments of a drying lake bed. All the individuals were histologically confirmed to be immature juveniles. All specimens were articulated and nearly complete, providing strong

evidence of juvenile mass mortality. Similar Asian bonebeds that preserve juveniles exclusively have been reported for Protoceratops (Hone et al. 2013) and Psittacosaurus

(Zhao et al. 2013). Evidence for juvenile sociality in North American taxa is less conclusive, as truly autochthonous bonebeds with complete or near-complete articulated skeletons are exceedingly rare. Nevertheless, the taphonomic and histological profile of the WBB offers a relatively robust data set that suggests the phenomenon of juvenile sociality was likely not limited to Asian ornithischians.

Conclusions

1.) The WBB is a parautochthonous assemblage that represents the mass death of a

group of early and late juvenile Gryposaurus sp. Evidence of hydraulic winnowing

and limited transport is present, however the condition and random orientation

of bones present suggest that the WBB represents a reliable picture of the living

group.

2.) Histological and morphological data indicates that the examined elements were

derived from juveniles approaching one and two years of age and, therefore, the

group was not made up of individuals from a single brood.

3.) Qualitative analysis of the bone tissue types and tissue organization, along with

absolute size of the elements, suggests that the WBB gryposaurs grew extremely

rapidly early in development. This coincides with previously published

histological examinations of other hadrosaur taxa (e.g., Horner et al. 2000;

Cooper et al. 2008).

4.) The discrete zonation of bone tissues observed in the WBB closely resembles

that of previously described “polar” hadrosaurines from the North Slope of

Alaska (Chinsamy et al. 2012). This suggests that the environmental controls

proposed by Chinsamy et al. (2012) for dinosaurs living at high latitudes may not

have been all that different than those acting on similar animals living in more

temperate coastal environments such as that of the Gryposaurus from this

bonebed study.

5.) The diagnosis of the WBB hadrosaurine as Gryposaurus increases the number of

hadrosaur taxa recognized from the Oldman Formation from two

(Brachylophosaurus canadensis, Hypacrosaurus stebingeri) to three. Additionally,

the presence of a diagnosed hadrosaur in the lower Oldman Formation increases

the taxonomic diversity within the lower unit of the formation.

APPENDIX A. HISTOLOGICAL PREPARATION

Preparation of slides was carried out in the Vertebrate Paleontology laboratory at the ROM and followed standard paleohistological methods (e.g., Chinsamy and Raath

1992; Padian and Lamm 2013) with lab-specific protocols following LeBlanc and Iwama

(2013). Six tibiae (TMP2008.045.0064; TMP2009.038.0008; TMP2009.038.0032;

TMP2010.078.0012; TMP2010.078.0014; TMP2010.078.0022) were selected from the larger pool of tibiae on the basis of size, overall quality of preservation, and condition of the midshaft diaphysis, and sectioned. The objective was to produce complete circumferential sections in order to capitalize on the advantages that complete slides have for documenting and analyzing growth marks (the most reliable way to diagnose a

LAG is to be able to trace it around the entire cortex).

Where necessary, specimens were consolidated with Vinac and Mercury

Adhesive M5T Thin Viscosity glue. Due to the friable nature of the specimens most required consolidation both before and after sectioning.

A plane of section was identified along the midshaft at the site of minimum circumference for each specimen. When this point was not practical as a sectioning point (i.e., TMP2009.038.0008 and TMP2010.078.0012) due to taphonomic loss of bone at this position, the specimens were sectioned at a point closest to the midshaft where a quality circumferential section could be obtained. Once identified, the plane of section was lightly sketched in with pencil.

In order to minimize the potential for damage to the bone during sectioning,

Technovit 5071 resin was used as a stabilizing agent for the initial cuts. This resin is very pliable during its pre-set period and gives the user a window of 10 to 15 seconds during which its putty-like viscosity allows it to be wrapped around the bone as a supporting collar. Once hardened, it acts as an effective pressure bandage, providing external support to the cortical bone during the cutting of the element. The Technovit resin was prepared using a ratio of two units of Technovit 5071 powder to one unit of Technovit

Universal Liquid, per the manufacturer’s instructions. For larger specimens, a total of approximately nine grams of Technovit 5071 powder was required to completely circumscribe the midshaft. Typically, three grams of powder and 1.5 grams of liquid were prepared at a time. The Technovit was applied to the bone by hand using nitrile gloves, following the pencil line traced around the midshaft. Once the Technovit had completely cured (approximately 20 to 30 minutes) the line was redrawn on top of the

Technovit with a black marker.

The bones were sectioned using a Buhler Isomet 1000 precision saw running at

225 RPM. For the initial cut, the saw was used in the table-saw position. This required the bone to be pushed through the blade manually, following the line drawn on the hardened Technovit. Due to the large circumference of the bones relative to the radius of the saw blade, all specimens required at least two cuts to completely section the bone, with the bone being rotated between 90 and 180 degrees between passes on the saw. Klean Clay was used as necessary to support the bone in whatever position was

required to properly align the bone for the cut. In order to minimize friction between the table and the clay while pushing the specimen through the saw, a small piece of dry paper towel was placed under the clay to act as a sled. Once the cut was complete, the specimen was rinsed and placed in a low-temperature drying oven.

All specimens required further consolidation or embedding on their cut surfaces.

Castolite AC resin was used for embedding very porous specimens (TMP2008.045.0064;

TMP2010.078.0014). Resin was prepared by the ounce, using thirteen drops of Eager

Hardener per one ounce of resin. A duct tape cuff was applied to the specimen before adding the resin in order to prevent the resin from overflowing and running down the sides of the specimen during subsequent vacuuming. For specimens that had significant breaks and cracks near the cut surface, thin duct tape strips were applied before the resin was prepared to act as pressure bandages to prevent resin from leaking.

Specimens were placed in a vacuum chamber immediately after the resin was added and they remained in the chamber until the resin was observed to have a frothy, boiling appearance (usually several minutes). This step pulled most of the bubbles to the surface of the resin where they could later be easily removed on the lapidary wheel.

Vacuum extraction could not be performed on larger specimens due the limiting size of the vacuum bubble. After vacuuming, specimens were set in a fume hood for 24 hours for the resin to cure. Due to high humidity (most specimens were prepared during a humid May and June) the resin was not always completely cured after 24 hours, and often required extra time under the fume hood. Specimens that were less porous were

not imbedded with resin but instead had their cut surfaces consolidated with Mercury

Adhesive M5T thin viscosity glue which would typically cure completely in several hours.

Once the consolidating and embedding agents were completely cured, specimens were ground flat on a Crystal Master Pro 12 lapidary wheel with a 400-grit disc. Due to complexities concerning the porosity of certain specimens, some required additional consolidation after being ground flat, which necessitated that they be re- ground. Once flat, specimens were then ground by hand with silicon carbide 600-grit on a glass plate. After grinding, specimens were placed in the oven to dry.

Specimens were mounted on Plexiglas slides which were hand ground on a glass plate with 600-grit until flat and uniformly frosted. Prior to mounting a specimen on a slide, both the specimen and the slide were cleaned with ethanol. Scotchweld CA-40 was used as an adhesive to mount most specimens, but resin was used for several larger specimens. Specimens mounted using CF-40 required several hours to cure, while those mounted with resin were left overnight.

After being mounted on slides, the specimens were trimmed to a thickness of approximately 0.7 mm on the Isomet saw. Larger specimens were trimmed by hand using the table saw set-up, while smaller slides were secured in a chuck and trimmed using the Isomet’s automatic cutting arm. Trimmed specimens were then ground on the lapidary wheel with a 400-grit disc until thin enough to be penetrated by light when held to a light source. Specimens were then hand-ground on glass plates with 600-grit and

with 1000-grit, as necessary, and examined periodically under the microscope until they reached the desired optical thickness.

Specimens were imaged using a Nikon AZ100 with a motorized stage and

Elements NIS software. Imaging utilized Z-stacking with a three-stack sequence and a

50-micrometer step. Slides were imaged under both plane polarized light and cross polarized light.

APPENDIX B. TAPHONOMIC MODIFICATION DATA

Specimen Taxon Element Abrasion Breakage Fracture Weathering 2006.0505.0001 Hadrosauridae Frontal 0 2 I 0 2006.050.0012 Hadrosauridae Limb shaft; tibia? 2 3 T,L 2006.050.0007 Hadrosauridae Metapodial 1 0 T,L 0 Hadrosauridae ? Flat chunk of bone 2 3 T,L 0 Hadrosauridae ? Limb shaft 0 3 T,L 0 Hadrosauridae ? Fragment 2008.45.46 Ceratopsidae Illium 1 3 T,I 1? 2008.45.49A Hadrosauridae Femur shaft=1, ends=2 0 T,L,I,coll? 0 2008.45.49B Hadrosauridae Radius or fibula? 0 1 T,L, coll 0 2008.45.49C Hadrosauridae Radius or fibula? 0 3 T,L 0 2008.45.49D Hadrosauridae Radius or rib fragments? 1 3 T,L,I 0 2008.45.49E Hadrosauridae Skull bone 3 3 T,L 0 2008.45.51 A Hadrosauridae Femur 0 2 T,L 0 2008.45.51 B Hadrosauridae Maxilla 0 0 T,I,L 0 2008.45.51 C Hadrosauridae Ischium? 1 3 T,I 1? 2008.45.52 A Hadrosauridae Neural spine Prox=2, Dist=0 3 T,I,L 0 2008.45.52 B Hadrosauridae Femur 0 1 T,I 0 2008.45.52 C Hadrosauridae ? 1 3 T,I 0 2008.45.58 A Hadrosauridae Pubis 0 3 L,T,I 0 2008.45.58 B Hadrosauridae Basicranium? 2 3 I 0 2008.45.58 C Hadrosauridae Phalanx? 2 3 T 0 2008.45.58 D Hadrosauridae Skull bone 0 3 L,T 0 2008.45.60A Hadrosauridae Femur Shaft=0, ends=2 0 T,L,I 0

Specimen Taxon Element Abrasion Breakage Fracture Weathering 2008.45.61A Hadrosauridae Scapula 1 3 I,T,L 0 2008.45.61 B Hadrosauridae Rib 1 3 T,S 0 2008.45.61 C Hadrosauridae Rib or jaw frag? 1 3 I 0 2008.45.61 D Hadrosauridae Rib frag? 0 3 I 0 2008.45.61 E Hadrosauridae Rib frag? 1 3 I 0 2008.45.63 Hadrosauridae Rib 0 3 T,S,L 0 Hadrosauridae Rib 1 3 L,T,S 0 2008.45.64 Hadrosauridae Tibia Shaft=0, Ends=2 1 T,I 0 2008.45.67A Hadrosauridae Femur Shaft=0, ends=2 0 T,L 0 2008.45.67B Hadrosauridae Femur Shaft=0, ends=3 0 T,L 0 2008.45.68 Hadrosauridae Femur, proximal Shaft=1, Ends=3 2 T,L 0 2009.038.0001 Hadrosauridae Dentary 0 0 S,T,L 0 2009.038.0002 Hadrosauridae Neural spine 1 1 L,T 0 Hadrosauridae ? 1 3 T 0 Hadrosauridae ? 1 3 I 0 2009.038.0003 Hadrosauridae Neural spine? 0 3 T, L 0 2009.038.0004 Hadrosauridae Ishium or rib fragment? 0 3 T 0 Hadrosauridae Rib fragment 0 3 T,L,I 0 2009.038.0006 Hadrosauridae ? 1 3 T,L,I 0 rostral element fragment? 2009.038.0007 Hadrosauridae Premaxilla? 1 3 I, C 0 2009.038.0008 Hadrosauridae Tibia Shaft=1, Ends=2 3 L,T,I 0 2009.038.0009 Hadrosauridae Illium or nasal? 1 3 I,T,L 0 2009.038.0010 Hadrosauridae Rib head 0 2 T,S 0 2009.038.0011 Hadrosauridae Rib? 1 3 T,I 0 2009.038.0012 Hadrosauridae Chevron? 2 3 I 0

Specimen Taxon Element Abrasion Breakage Fracture Weathering 2009.038.0013 Hadrosauridae Rib 0 3 T 0 2009.038.0015 Hadrosauridae Rib? Ischium? 2 3 L,T 0 2009.038.0016 Hadrosauridae Femur shaft=0, ends=2 1 T,L,I 0 2009.038.0017 (1 of 2) Hadrosauridae Dentary 0 2 S,T,L 0 2009.038.0017 (2 of 2) Hadrosauridae Tibia 0 0 T,L 0 2009.038.0018 Hadrosauridae Rib fragment 1 3 S,T,L 0 2009.038.0019 Hadrosauridae ? 2 3 L 0 2009.038.0021 Hadrosauridae ? 2 3 I,T 0 2009.038.0022 Hadrosauridae Rib frag 1 3 S,I,T 0 2009.038.0024 Hadrosauridae Rib or angular fragment? 1 3 T,I 0 2009.038.0025 Hadrosauridae Rib frag 0 3 T 0 2009.038.0026 Hadrosauridae Radius or ischium? Shaft=0, D.end=2 1 T,L 0 2009.038.0027 Hadrosauridae Rib fragment 1 3 T,L 0 2009.038.0028 Hadrosauridae Limb end? 2 1 T 0 2009.038.0029 Hadrosauridae Tendon fragment 0 3 T 0 2009.038.0030 Hadrosauridae Tendon fragment 0 3 T,L 0 2009.038.0032 (1 of 2) Hadrosauridae Tibia Shaft=0, ends=2 0 T,I,L 0 2009.038.0032 (2 of 2) Hadrosauridae Dentary 0 0 S,T,L 0 Hadrosauridae Ischium? Or premax? 0 3 T,L 0 2009.038.0033 Hadrosauridae ? 2 3 I 0 2009.038.0034 Hadrosauridae Rib fragment 2 3 T,L 0 2009.038.0035 Hadrosauridae Rib fragment? 0 3 T,S 0 2009.038.0038 Hadrosauridae ? 3 3 T 0 91

Specimen Taxon Element Abrasion Breakage Fracture Weathering 2009.038.0039 Hadrosauridae Tooth crown 2009.038.0043 ? Unidentified rib or limb shaft 0 3 T 0 2009.038.0044 Tyrannosauridae Tooth crown 0 1 T,I 0 2009.038.0045 Hadrosauridae Neural spine Prox=3, Dist=0 3 T,L 0 2009.038.0046 Hadrosauridae ? 0 3 I 0 2009.038.0047 Hadrosauridae Rib head 0 3 T,L 0 2009.038.0048 Hadrosauridae Rib frag 0 3 T 0 2009.038.0049 Hadrosauridae Humerus Shaft=0, Ends=2 0 T,L,I 0 2009.038.0050 Hadrosauridae Femur Shaft=0, End=3 2 I,T,L 0 2009.038.0052 (1 of 2) Hadrosauridae Ischium 1 1 T,L 0 2009.038.0052 (2 of 2) Hadrosauridae Ischium 0 3 T,I 0 2009.038.0053 Hadrosauridae Nasal? 3 3 I, T 0 Hadrosauridae Rib frag 0 3 T,L 0 2009.038.0054 Stegoceras Supraorbital 0 3 T 0 2009.038.0055 Hadrosauridae Femur Shaft=0, Ends=2 0 T 0 2009.038.0056 Hadrosauridae Tibia 0 0 S,L, T 0 2009.038.0057 Hadrosauridae ? 2 3 I, C 0 2009.038.0058 Hadrosauridae Jugal 0 3 T,I,S? 0 2009.038.0061 Hadrosauridae Scapula 0 0 T,I 0 2009.038.0071 Hadrosauridae Rib fragment 0 3 T,L 0 2009.038.0072 Hadrosauridae Pubis 0 3 T,I 0 2010.078.0001 Hadrosauridae maxilla? 0 3 T,S? 0 2010.078.0002 Hadrosauridae lacrimal or jugal? 0 3 T,L 0 2010.078.0003 Hadrosauridae Rib 0 3 T 0

Specimen Taxon Element Abrasion Breakage Fracture Weathering 2010.078.0004 Hadrosauridae Rib fragment 0 3 T 0 2010.078.0005 Hadrosauridae ? 2010.078.0006 Hadrosauridae Jaw fragment; maxilla? 2010.078.0007 Hadrosauridae ? 1 3 I 0 2010.078.0008 Hadrosauridae Dentary; part of dental battery 2 3 X 0 2010.078.0009 Hadrosauridae Nasal? 0 3 L, T 1 2010.078.0012 Hadrosauridae Tibia 0 0 T,L 2 2010.078.0014 Hadrosauridae Tibia Shaft=0, ends=3 0 T,I 0 Hadrosauridae Chunks of prox tibia 2010.078.0015 Hadrosauridae ? 0 3 T 0 2010.078.0016 Hadrosauridae rostral element fragment? Maxilla? 2 3 L,T 0 2010.078.0017 Hadrosauridae Limb end, distal 2 1 T 0 2010.078.0018 Hadrosauridae Rib fragment 0 3 T 0 2010.078.0020 Hadrosauridae Tarsal 1 1 X 0 2010.078.0022 Hadrosauridae Tibia Shaft=1, Ends=3 0 T,I, S? 0 Hadrosauridae Maxilla 0 ? T,I 0 2010.078.0025 Hadrosauridae Rib fragments (4) 2010.078.0026 Hadrosauridae Humerus Shaft=0, Ends=2 0 T,L 0 2010.????? Maxila 0 3 T,S?,I 0

REFERENCES

1978. Alberta Historical Resources Act, H-9 RSA 2000. Available from the Alberta

Queen’s Printer.

Adams, J.S., and Organ, C.L. 2005. Histologic determination of ontogenetic patterns and

processes in hadrosaurian ossified tendons. Journal of Vertebrate Paleontology,

25(3): 614–622.

Bakker, R.T. 1975. Dinosaur renaissance. Scientific American, 232(4): 58–78.

Behrensmeyer, A.K. 1978. Taphonomic and ecologic information from bone weathering.

Paleobiology, 4(2): 150–162.

Bell, P.R. 2012. Standardized terminology and potential taxonomic utility for

hadrosaurid skin impressions: a case study for Saurolophus from Canada and

Mongolia. Plos ONE, 7(2): e31295. doi:10.1371/journal.pone.0031295.

Bell, P.R., and Evans, D.C. 2010. Revision of the status of Saurolophus (Hadrosauridae)

from California, USA. Canadian Journal of Earth Sciences, 47: 1417–1426.

Bell, P.R., and Campione, N.E. 2014. Taphonomy of the Danek Bonebed: a

monodominant Edmontosaurus (Hadrosauridae) bonebed from the Horseshoe

Canyon Formation, Alberta. Canadian Journal of Earth Sciences 51(11): 992–

1006.

Brouwers, E.M., Clemens, W.A., Spicer, R.A., Ager, T.A., Carter, L.D., and Sliter, W.V.

1987. Dinosaurs on the North Slope: high latitude, latest Cretaceous

environments. Science, 237: 1608–1610.

Brown, B. 1914. Corythosaurus casuarius, a new crested dinosaur from the Belly River

Cretaceous, with provisional classification of the family Trachodontidae. Bulletin

of the American Museum of Natural History, 33: 549–558.

Brown, B. 1916. A new crested trachodont dinosaur, Prosaurolophus maximus. Bulletin

of the American Museum of Natural History, 35: 701–708.

Brown, C.M., Russell, A.P., and Ryan, M.J. 2009. Pattern and transition of surficial bone

texture of the centrosaurine frill and their ontogenetic and taxonomic

implications. Journal of Vertebrate Paleontology, 29(1): 132–141.

Bryant, H.N., and Russell, A.P. 1992. The role of phylogenetic analysis in the inference of

unpreserved attributes of extinct taxa. Philosophical Transactions of the Royal

Society B: Biological Sciences, 337(1282): 405–418.

Buffetaut, E., and Mazin, J. 2003. Evolution and palaeobiology of pterosaurs. Geological

Society, London, Special Publications, 217: 1–3. de Buffrenil, V., and Buffetaut, E. 1981. Skeletal growth lines in an Eocene crocodilian

skull from Wyoming as an indicator of ontogenetic age and paleoclimatic

conditions. Journal of Vertebrate Paleontology, 1(1): 57–65.

Campione, N.E., and Evans, D.C. 2011. Cranial growth and variation in edmontosaurs

(Dinosauria: Hadrosauridae): implications for latest Cretaceous megaherbivore

diversity in North America. PLoS ONE 6(9): e25186. doi:

10.1371/journal.pone.0025186.

Cerda, I.A., and Powell, J.E. 2010. Dermal armor histology of Saltasaurus loricatus, an

Upper Cretaceous sauropod dinosaur from Northwest Argentina. Acta

Palaeontologica Polonica, 55(3): 389–398.

Chinsamy, A., and Raath, M.A. 1992. Preparation of fossil bone for histological

examination. Palaeontologia Africana, 29: 39–44.

Chinsamy, A. 2005. The microstructure of dinosaur bone: deciphering biology with fine-

scale techniques. John Hopkins University Press. 216 p.

Chinsamy, A., Thomas, D.B., Tumarkin-Deratzian, A.R., and Fiorillo, A.R. 2012.

Hadrosaurs were perennial polar residents. The Anatomical Record, 295: 610–

614.

Colbert, E.H. 1948. A hadrosaurian dinosaur from New Jersey. Proceedings of the

Academy of Natural Sciences of Philadelphia, 100: 23–37.

Colson, M.C., Colson, R.O., and Nellermoe, R. 2004. Stratigraphy and depositional

environments of the upper Fox Hills and lower Hell Creek formations at the

Concordia hadrosaur site in northwestern South Dakota. Rocky Mountain

Geology, 39(2): 93–111.

Cooper, L.N., Lee, A.H., Taper, M.L., and Horner, J.R. 2008. Relative growth rates of

predator and prey dinosaurs reflect effects of predation. Proceedings of the

Royal Society, Biological Sciences, 275: 2609–2615.

Currie, P.J. 1998. Possible evidence of gregarious behavior in Tyrannosaurids. Gaia, 15:

271–277.

Currie, P.J. Badamgarav, D., and Koppelhus, E.B. 2003. The first Late Cretaceous

footprints from the Nemegt locality in the Gobi of Mongolia." Ichnos, 10(1): 1–

13.

Currie, P.J., and Koppelhus, E.B. (eds.) 2005. Dinosaur Provincial Park: a spectacular

ancient ecosystem revealed. Indiana University Press. 672 p.

Davies, K.L. 1987. Duck-bill dinosaurs (Hadrosauridae, Ornithischia) from the North

Slope of Alaska. Journal of Paleontology, 61(1): 198–200. de Klerk, W.J., Forster, C.A., Sampson, S.D., Chinsamy, A., and Ross, C.F. 2000. A new

coelurosaurian dinosaur from the early cretaceous of South Africa. Journal of

Vertebrate Paleontology, 20(2): 324–332.

De Ricqles, A.J., Padian, K., Horner, J.R., and Francillon-Viellot, H. 2000. Palaeohistology

of the bones of pterosaurs (Reptilia: Archosauria): anatomy, ontogeny, and

biomechanical implications. Zoological Journal of the Linnean Society, 129(3):

349–385.

Eberth, D.A. 2005. The Geology. In Dinosaur Provincial Park. Edited by P.J. Currie and

E.B. Koppelhus. Indiana University Press, Bloomington. pp. 54–82.

Eberth, D.A., and Hamblin, A.P. 1993. Tectonic, stratigraphic, and sedimentologic

significance of a regional discontinuity in the upper Judith River Group (Belly

River wedge) of southern Alberta, Saskatchewan, and northern Montana.

Canadian Journal of Earth Sciences, 30(1): 174–200.

Eberth, D.A., and Evans, D.C. 2011. International Hadrosaur Symposium, Geology and

Palaeontology of Dinosaur Provincial Park, Alberta field trip guidebook, Special

Publication of the Royal Tyrrell Museum: 52.

Eberth, D.A., and Evans, D.C. 2014. Hadrosaurs. Indiana University Press, Bloomington.

640 p.

Efremov, I.A. 1940. Taphonomy: a new branch of paleontology. Pan-American Geologist,

74(2): 81–93.

Erickson, G.M. 2005. Assessing dinosaur growth patterns: a microscopic revolution.

Trends in Ecology and Evolution, 20: 677–684.

Erickson, G.M., and Druckenmiller, P.S. 2011. Longevity and growth rate estimates for a

polar dinosaur: a Pachyrhinosaurus (Dinosauria: Neoceratopsia) specimen from

the North Slope of Alaska showing a complete developmental record. Historical

Biology, 23(4): 327–334.

Erickson, G.M., and Tumanova, T.A. 2000. Growth curve of Psittacosaurus mongoliensis

Osborn (Ceratopsia: Psittacosauridae) inferred from long bone histology.

Zoological Journal of the Linnean Society, 130: 551–566.

Evans, D.C., Schott, R., Larson, D., Brown, C.M. and Ryan, M.J. 2013. The oldest North

American pachycephalosaurid and the hidden diversity of small-bodied

ornithischian dinosaurs. Nature Communications, 4: 1828.

Fiorillo, A.R. 1988. Taphonomy of Hazard Homestead Quarry (Ogalla Group), Hitchcock

County, Nebraska. Contributions to Geology, University of Wyoming, 26: 57–97.

Fiorillo, A.R., and Gangloff, R.A. 2001. The caribou migration model for arctic hadrosaurs

(Dinosauria: Ornithischia): a reassessment. Historical Biology, 15: 323–334.

Fiorillo, A.R., Contessi, M., Kobayashi, Y., and McCarthy, P.J. 2014. Theropod tracks from

the lower Cantwell Formation (Upper Cretaceous) of Denali National Park,

Alaska, USA with comments of theropod diversity in an ancient, high-latitude

terrestrial ecosystem. In Fossil Footprints of Western North America. Edited by

M.G. Lockley and S.G. Lucas. New Mexico Museum of Natural History and

Science Bulletin 62. pp. 429–440.

Fowler, D.W., Woodward, H.N., Freedman, E.A., Larson, P.L., Horner, J.R. 2011.

Reanalysis of “Raptorex kriegsteini”: a juvenile tyrannosaurid dinosaur from

Mongolia. PLoS ONE 6(6): e21376. doi: 10.1371/journal.pone.0021376.

Gallagher, W. B. 1997. When dinosaurs roamed New Jersey. Rutgers University press,

N.J.

Gates, T.A. 2005. The late Jurassic Cleveland-Lloyd dinosaur quarry as a drought-induced

assemblage. Palaios, 20(4): 363-375.

Gates, T.A, and Sampson, S.D. 2007. A new species of Gryposaurus (Dinosauria:

Hadrosauridae) from the late Campanian Kaiparowits Formation, southern Utah,

USA. Zoological Journal of the Linnean Society, 151: 351–376.

Godefroit, P., Bolotsky, Y., and Alifanov, V. 2003. A remarkable hollow-crested

hadrosaur from Russia: an Asian origin for lambeosaurines. Comptes Rendus

Palevol 2(2): 143–151.

Haynes, G. 1983. Frequencies of spiral and green-bone fractures on ungulate limb bones

in modern surface assemblages. American Antiquity, 48(1): 102–114.

Head, J.J. 1998. A new species of basal hadrosaurid (Dinosauria, Ornithischia) from the

Cenomanian of Texas. Journal of Vertebrate Paleontology, 18: 718–738.

Hieronymus, T.L., Witmer, L.M., Tanke, D.H., and Currie, P.J. 2009. The facial integument

of Centrosaurine ceratopsids: morphological and histological correlates of novel

skin structures. The Anatomical Record, 292: 1370–1396.

Hone, D.W.E., Farke, A.A., Watabe M., Shigeru S., and Tsogtbaatar K. 2014. A new mass

mortality of juvenile Protoceratops and size-segregated aggregation behaviour in

100

juvenile non-avian dinosaurs. PLoS ONE, 9(11): e113306. doi:

10.1371/journal.pone.0113306.

Hone, D.W.E., Sullivan, C., Zhao, Q., Wang, K., and Xing, X. 2014. Body size distribution in

a death assemblage of a colossal hadrosaurid from the Upper Cretaceous of

Zhucheng, Shandong Province, China." In Hadrosaurs. Edited by D.A. Eberth and

D.C. Evans. Indiana University Press, Bloomington. pp. 524–531.

Horner, J.R. 1982. Evidence of colonial nesting and ‘site fidelity’ among ornithischian

dinosaurs. Nature, 297: 675–676.

Horner, J.R. 1989. The Mesozoic terrestrial ecosystems of Montana. Montana Geological

Society Guidebook, 1989: 153–162.

Horner, J.R. 1992. Cranial morphology of Prosaurolophus (Ornithischia: Hadrosauridae)

with description of two new hadrosaurid species and an evaluation of

hadrosaurid phylogenetic relationships. Museum of the Rockies Occasional

Paper 2, Museum of the Rockies. 199 p.

Horner, J.R. 1999. Egg clutches and embryos of two hadrosaurian dinosaurs. Journal of

Vertebrate Paleontology, 19: 607–611.

Horner, J.R., and Makela, R. 1979. Nest of juveniles provides evidence of family

structure among dinosaurs. Nature, 282: 296–298.

Horner, J.R., and Currie, P.J. 1994. Embryonic and neonatal morphology and ontogeny of

a new species of Hypacrosaurus (Ornithischia: Lambeosauridae) from Montana 101

and Alberta. In Dinosaur Eggs and Babies. Edited by K. Carpenter, K.F. Hirsch, and

J.R. Horner. Cambridge University Press, Cambridge. pp. 312–336.

Horner, J.R., Padian, K., and de Ricqles, A. 2001. Comparative osteohistology of some

embryonic and perineal archosaurs: developmental and behavioral implications

for dinosaurs. Paleobiology, 27(1): 39–58.

Horner, J.R., de Ricqles, A., and Padian, K. 1999. Variation in dinosaur skeletochronology

indicators: implications for age assessment and physiology. Paleobiology, 25(3):

295–304.

Horner, J.R., de Ricqles, A., and Padian, K. 2000. Long bone histology of the hadrosaurid

dinosaur Maiasaura peeblesorum: growth dynamics and physiology based on an

ontogenetic series of skeletal elements. Journal of Vertebrate Paleontology,

20(1): 115–129.

Horner, J.R., Weishampel, D.B., and Forster, C.A. 2004. Hadrosauridae. In The

Dinosauria. 2nd ed. Edited by D.B. Weishampel, P. Dodson, and H. Osmólska.

University of California Press, Berkeley. pp. 438–463.

Houde, P. 1987. Histological evidence for the systematic position of Hesperornis

(Odontornithes: Hesperornithiformes). The Auk, 104(1): 125–129.

Kirkland, J.I., Hernandez-Rivera, R., Gates, T., Paul, G.S., Nesbitt, S., Serrano-Branas, C.I.,

and Garcia-De La Garza, J.P. 2006. Large hadrosaurine dinosaurs from the latest

Campanian of Coahuila, Mexico. In Late Cretaceous Vertebrates from the

102

Western Interior. Edited by S.G. Lucas and R.M. Sullivan. New Mexico Museum of

Natural History and Science Bulletin 35. pp. 299–315.

Klein, N., Christian, A., and Sander, P.M. 2012. Histology shows that elongated neck ribs

in sauropod dinosaurs are ossified tendons. Biology Letters, 11(5). DOI:

10.1098/rsbl.2012.0778.

Lambe, L.M. 1914. On Gryposaurus notabilis, a new genus and species of trachodont

dinosaur from the Belly River Formation of Alberta, with a description of the

skull of Chasmosaurus belli. The Ottawa Naturalist 27(11): 145–155.

Lauters, P., Bolotsky, Y.L., Van Itterbeeck, J., and Godefroit, P. 2008. Taphonomy and age

profile of a latest Cretaceous dinosaur bone bed in Far Eastern Russia. Palaios,

23(3): 153–162.

LeBlanc, A., and Iwama, B. 2013. ROM [Royal Ontario Museum] V.P. Lab Thin-sectioning

procedure: Unpublished Royal Ontario Museum Vertebrate Paleontology lab

manual. 5 p.

Lehman, T.M. 1990. The ceratopsian subfamily Chasmosaurinae: sexual dimorphism and

systematics. In Dinosaur Systematics: Approaches and Perspectives. Edited by

P.J. Currie and K. Carpenter. Cambridge University Press, Cambridge. pp. 211–

229.

103

Longrich, N. 2008. A new, large ornithomimid from the Cretaceous Dinosaur Park

Formation of Alberta, Canada: implications for the study of dissociated dinosaur

remains. Palaeontology, 51(4): 983–997.

Lucas, S.G., Sullivan, R.M., Jasinski, S.E., and Ford, T.L. 2011. Hadrosaur footprints from

the Upper Cretaceous Fruitland Formation, San Juan Basin, New Mexico, and the

ichnotaxonomy of large ornithopod footprints. New Mexico Museum of Natural

History Bulletin, 53: 357–362.

Moodie, R.L. 1917. The structure and growth of the plesiosaurian propodial. Journal of

Morphology, 27(2): 401–411.

Moodie, R.L. 1928. The histological nature of ossified tendons found in dinosaurs.

American Museum Novitates, 311:16.

Morris, W.J. 1973. A review of Pacific coast hadrosaurs. Journal of Paleontology, 47:

551–561.

Padian, K., Horner, J.R., and de Ricqles, A. 2004. Growth in small dinosaurs and

pterosaurs: the evolution of archosaurian growth strategies. Journal of

Vertebrate Paleontology, 24(3): 555–571.

Padian, K., and Lamm, E.T. (eds.) 2013. Bone histology of fossil tetrapods: advancing

methods, analysis, and interpretation. University of California Press. 298 p.

104

Parks, W. A. 1919. Preliminary description of a new species of trachodont dinosaur of

the genus Kritosaurus, Kritosaurus incurvimanus. Transactions of the Royal

Society of Canada, 3(13): 51–59.

Parks, W. A. 1922. Parasaurolophus walkeri, a new genus and species of crested

Trachodont dinosaur. University of Toronto Studies, Geological Series, 13: 1–32.

Prieto‐Marquez, A. 2010. Global phylogeny of Hadrosauridae (Dinosauria: Ornithopoda)

using parsimony and Bayesian methods. Zoological Journal of the Linnean

Society 159(2): 435–502.

Parks, W.A. 1923. Corythosaurus intermedius, a new species of Trachodont dinosaur.

University of Toronto Studies, Geological Series, 15: 1–57.

Reid, R.E.H. 1985. On supposed haversian bone from the hadrosaur Anatosaurus, and

the nature of compact bone in dinosaurs. Journal of Paleontology, 59(1): 140–

148.

Reizner, J.A. 2010. An ontogenetic series and population histology of the ceratopsid

dinosaur Einiosaurus procurvicornis. M.S. thesis, Montana State University. 109

Rodriguez de la Rosa, R.A. 2007. Hadrosaurian footprints from the Late Cretaceous

Cerro Del Pueblo Formation of Coahuila, Mexico. In 4th European Meeting on the

Palaeontology and Stratigraphy of Latin America Cuadernos del Museum

Geominero, Madrid, Spain, No. 8, pp. 339–343.

105

Rogers, R.R. 1990. Taphonomy of three dinosaur bone beds in the upper Cretaceous

Two Medicine Formation of northwestern Montana: evidence for drought-

related mortality. Palaios, 5(5): 394:413.

Rogers, R.R., Eberth, D.A., and Fiorillo, A.R. 2008. Bonebeds: genesis, analysis, and

paleobiological significance. The University of Chicago Press, Chicago. 512 p.

Ryan, M.J. 2007. A new basal centrosaurine ceratopsid from the Oldman Formation,

southeastern Alberta. Journal of Paleontology: 81(2): 376–396.

Ryan, M.J., and Russell, A.P. 2001. The dinosaurs of Alberta (exclusive of Aves). In

Mesozoic Vertebrate Life: New Research Inspired by the Paleontology of Philip J.

Currie. Edited by D. Tanke and K. Carpenter. Indiana University Press,

Bloomington. pp. 279–297.

Ryan, M.J., Russell, A.P., Eberth, D.A., and Currie, P.J. 2001. The taphonomy of a

Centrosaurus (Ornithischia: Ceratopsidae) bone bed from the Dinosaur Park

Formation (Upper Campanian), Alberta, Canada, with comments on cranial

ontogeny. Palaios, 16(5): 482–506.

Ryan, M.J., and Russell, A.P. 2005. A new centrosaurine ceratopsid from the Oldman

Formation of Alberta and its implications for centrosaurine taxonomy and

systematics. Canadian Journal of Earth Sciences, 42(7): 1369–1387.

106

Ryan, M.J., Evans, D.C., and Shepard, K.M. 2012. A new ceratopsid from the Foremost

Formation (middle Campanian) of Alberta. Canadian Journal of Earth Sciences,

49: 1251–1262.

Saitta, E.T. 2015. Evidence for sexual dimorphism in the plated dinosaur Stegosaurus

mjosi (Ornithischia, Stegosauria) from the Morrison Formation (Upper Jurassic)

of Western USA. PLoS One, 10(4): e0123503. doi:

10.1371/journal.pone.0123503.

Sampson, S.D., Ryan, M.J., and Tanke, D.H. 1997. Craniofacial ontogeny in centrosaurine

dinosaurs (Ornithischia: Ceratopsidae): taxonomic and behavioral implications.

Zoological Journal of the Linnean Society, 121(3): 293–337.

Sampson, S.D. 2012. Dinosaurs of the lost continent. Scientific American, 306(3):40-47.

Sander, P.M. 2000. Longbone histology of the Tendaguru sauropods: implications for

growth and biology. Paleobiology, 26(3): 466–488.

Sander, P.M., Mateus, O., Laven, T., and Knotschke, N. 2006. Bone histology indicates

insular dwarfism in a new Late Jurassic sauropod dinosaur. Nature, 441: 739–

741.

Scannella, J.B., and Horner, J.R. 2010. Torosaurus Marsh, 1891, is Triceratops Marsh,

1889 (Ceratopsidae: Chasmosaurinae): synonymy through ontogeny. Journal of

Vertebrate Paleontology, 30(4): 1157–1168.

107

Scherzer, B.A., and Varricchio, D.J. 2010. Taphonomy of a juvenile lambeosaurine

bonebed from the Two Medicine Formation (Campanian) of Montana, United

States. Palaios, 25: 780–795.

Scott, E.E., Ryan, M.J., and Evans, D.C. 2014. A Gryposaurus bone bed from the Oldman

Formation (Campanian) of south-eastern Alberta with implications for dinosaur

sociality. Rocky Mountain and Cordilleran Joint Section Meeting, Geological

Society of America.

Sternberg, C.M. 1935. Hooded hadrosaurs of the Belly River series of the upper

Cretaceous: a comparison, with descriptions of new species. National Museum of

Canada Department of Mines Bulletin, 77: 1–37.

Sternberg, C.M. 1953. A new hadrosaur from the Oldman formation of Alberta:

discussion of nomenclature. Bulletin of the National Museum of Canada, 128:

275–286.

Straight, W.H., Davis, G.L., Skinner, H.C.W., Haims, A., McClennan, B.L., and Tanke, D.H.

2009. Bone lesions in hadrosaurs: computed tomographic imaging as a guide for

paleohistologic and stable-isotopic analysis. Journal of Vertebrate Paleontology,

29(2): 315–325.

Tumarkin-Deratzian, A.R. 2003. Bone surface textures as ontogenetic indicators in

extant and fossil archosaurs: Macroscopic and histological evaluations. Ph.D.

dissertation, University of Pennsylvania. 333 p.

108

Tumarkin-Deratzian, A.R. 2010. Histological evaluation of ontogenetic bone surface

texture changes in the frill of Centrosaurus apertus. In New Perspectives on

Horned Dinosaurs. Edited by M.J. Ryan, B.J. Chinnery-Allgeier, and D.A. Eberth.

Indiana University Press, Bloomington. pp. 251–263.

Vanderven, E., Burns, M.E., and Currie, P.J. 2014. Histologic growth dynamic study of

Edmontosaurus regalis (Dinosauria: Hadorsauridae) from a bonebed assemblage

of the Upper Cretaceous Horseshoe Canyon Formation, Edmonton, Alberta,

Canada. Canadian Journal of Earth Sciences, 51: 1023–1033.

Varricchio, D.J. 1993. Bone microstructure of the Upper Cretaceous theropod dinosaur

Troodon formosus. Journal of Vertebrate Paleontology, 13(1): 99–104.

Varricchio, D.J. 1995. Taphonomy of Jack's Birthday Site, a diverse dinosaur bonebed

from the Upper Cretaceous Two Medicine Formation of Montana.

Palaeogeography, Palaeoclimatology, Palaeoecology, 114(2): 297–323.

Varricchio, D.J. and Horner, J.R. 1993. Hadrosaurid and lambeosaurid bone beds from

the Upper Cretaceous Two Medicine Formation of Montana: taphonomic and

biologic implications. Canadian Journal of Earth Sciences, 30(5): 997–1006.

Varricchio, D.J., Sereno, P.C., Xijin, Z., Lin, T., Wilson, J.A., and Lyon, G.H. 2008. Mud-

trapped herd captures evidence of distinctive dinosaur sociality. Acta

Palaeontologica Polonica, 53(4): 567–578.

109

Wilson, G.E. 1927. A study in American paleohistology. The American Naturalist,

61(677): 555–565.

Witmer, L.M. 1995. The extant phylogenetic bracket and the importance of

reconstructing soft tissues in fossils. In Functional Morphology in Vertebrate

Paleontology. Edited by J. Thomason. Cambridge University Press, Cambridge.

pp. 19–33.

Xing, H., Wang, D., Han, F., Sullivan, C., Ma, Q., He, Y., Hone, D.W.E, Yan, R., Du, F., and

Xu, X. 2014. A new basal hadrosauroid dinosaur (Dinosauria: Ornithopoda) with

transitional features from the Late Cretaceous of Henan Province, China. PLoS

One, 9(6): e98821. doi: 10.1371/journal.pone.0098821.

You, H., Luo, Z., Shubin, N.H., Witmer, L.M., Tang, Z., and Tang, F. 2003 The earliest

known duck-billed dinosaur from deposits of late early Cretaceous age in

northwest China and hadrosaur evolution. Cretaceous Research, 24: 347–355.

Zhao, Q., Barrett, P.M., Xing, X., and Sander, P.M. 2013. Juvenile-Only Clusters and

Behaviour of the Early Cretaceous Dinosaur Psittacosaurus. Acta Palaeontologica

Polonica, 59(4):827–833.

110