Skull Anatomy and Relationships of Jingshanosaurus Xinwaensis (Dinosauria: Sauropodomorpha) from the Lower Jurassic Lufeng Formation of Yunnan Province, China By

Home , Anchisauria, Anchisaurus, Antetonitrus, Blikanasaurus, Buriolestes, Chromogisaurus

Skull Anatomy and Relationships of Jingshanosaurus xinwaensis (Dinosauria: Sauropodomorpha) from the Lower Jurassic Lufeng Formation of Yunnan Province, China by

Joshua Sundgren, B.S.

A Thesis

Geoscience

Submitted to the Graduate Faculty of Texas Tech University in Partial Fulfillment of the Requirements for the Degree of

MASTER OF SCIENCE

Approved

Dr. Sankar Chatterjee Chair of the Committee

Dr. Thomas Lehman

Dr. James Barrick

Mark Sheridan Dean of the Graduate School

May, 2021

ACKNOWLEDGEMENTS

First, I would like to thank my advisor and committee chair, Dr. Sankar

Chatterjee, for giving me this incredible opportunity. His support and guidance have been invaluable while working on this project, especially with all of the challenges over the past year. I would also like to thank my other committee members, Dr. James Barrick and Dr. Tom Lehman, for all of their assistance, both on this project and throughout my entire time at Texas Tech.

I am extremely grateful to Kendra Dean-Wallace and John-Henry Voss of the

Museum of Texas Tech University for their help throughout all stages of this project. I would also like to thank Dr. Hai-Lu You of the Institute of Vertebrate Paleontology and

Paleoanthropology for providing the phylogenetic data which played such a key role in this research. I am very appreciative of all of the help I’ve received from Celeste

Yoshinobu, throughout my entire time at Texas Tech University.

Finally, I cannot thank my parents, Gary and Stacy, enough for all of their support and everything they have done for me. I would not be where I am today without them.

Texas Tech University, Joshua Sundgren, May 2021

TABLE OF CONTENTS ACKNOWLEDGEMENTS ...... ii

ABSTRACT ...... v

LIST OF FIGURES ...... vi

1. INTRODUCTION ...... 1

1.1 Materials and Methods ...... 9 1.2 Institutional Abbreviations ...... 10 2. GEOLOGIC SETTING ...... 11

3. PREVIOUS WORK ...... 21

3.1 “Gyposaurus” sinensis ...... 21 3.2 Lufengosaurus ...... 22 3.3 Yunnanosaurus ...... 24 3.4 Chuxiongosaurus ...... 27 3.5 Xixiposaurus ...... 28 3.6 Xingxiulong ...... 28 3.7 Yizhousaurus ...... 30 3.8 Irisosaurus ...... 32 3.9 Jingshanosaurus ...... 34 4. SKULL DESCRIPTION OF JINGSHANOSAURUS ...... 37

4.1 General Features ...... 37 4.2 Dermal Bones of the Skull Roof ...... 38 4.2.1 Premaxilla ...... 38 4.2.2 Maxilla ...... 39 4.2.3 Nasal ...... 40 4.2.4 Frontal ...... 41 4.2.5 Prefrontal...... 42 4.2.6 Postorbital ...... 42 4.2.7 Quadrate ...... 43 4.3 Palatal Complex ...... 46 4.3.1 Vomer ...... 46 4.3.2 Pterygoid ...... 46 4.3.3 Ectopterygoid ...... 47 4.4 Lower Jaw ...... 50

iii

Texas Tech University, Joshua Sundgren, May 2021

4.4.1 Dentary ...... 50 4.4.2 Surangular ...... 51 4.4.3 Articular ...... 51 4.5 Dentition ...... 55 5. PHYLOGENETIC ANALYSIS ...... 60

6. SUMMARY ...... 64

BIBLIOGRAPHY ...... 66

APPENDICES A. LIST OF PHYLOGENETIC CHARACTERS ...... 74

Texas Tech University, Joshua Sundgren, May 2021

ABSTRACT

The basal sauropodomorphs are an important group of saurischian dinosaurs which include some of the earliest dinosaurs known to researchers, with the oldest taxa dating to the Late Triassic. Different members of the basal sauropodomorphs are closely related to several other groups, including the immediate ancestors to dinosaurs, theropods, and the true sauropods. Because of these close relations, a good understanding of the phylogenetic relationships between the basal sauropodomorphs is key to a broader understanding of early dinosaurs. Jingshanosaurus xinwaensis is an

Early Jurassic sauropodomorph which has been recovered previously as a basal member of the clade Sauropodiformes, which eventually gave rise to the true sauropods.

However, J. xinwaensis has suffered from a lack of cranial material for research, a problem that this study addresses. Specimen IVPP-13246 consists of 14 previously undescribed and disarticulated cranial bones from the skull roof, palatal complex and the lower jaw, as well as teeth preserved in good condition. The teeth are of particular interest partially because of their condition and also because of their unique form which is more similar to those seen in sauropods than in basal sauropodomorphs. These bones are described here and have characters scored and entered into a data matrix from another recent study. A phylogeny is then reconstructed from this data using PAUP*4.0a169.

The results of this analysis do not show Jingshanosaurus as having changed position which lends robust support to the findings of previous studies. There is potential for future studies, particularly in relation to bones that had not been described for earlier skulls, such as the nasal and the vomer.

Texas Tech University, Joshua Sundgren, May 2021

LIST OF FIGURES

2.1 Earth in the Early Jurassic ...... 12 2.2 Lufeng, China ...... 15 2.3 Detailed Locality Map ...... 17 2.4 Stratigraphy Column ...... 19 4.1 Jingshanosaurus skull ...... 37 4.2 Bones of the Skull Roof ...... 44 4.3 Line drawings of skull roof bones ...... 45 4.4 Palate Bones ...... 48 4.5 Line drawings of palatal complex bones ...... 49 4.6 Lower Jaw Bones ...... 53 4.7 Line drawings of lower jaw bones ...... 54 4.8 Jingshanosaurus dentition ...... 58 4.9 Line drawings of Jingshanosaurus dentition ...... 59 5.1 Sauropodomorph Phylogeny ...... 62

Texas Tech University, Joshua Sundgren, May 2021

CHAPTER 1

INTRODUCTION

Sauropodomorpha is a clade of long-necked, herbivorous saurischian dinosaurs that includes the sauropods and their basal relatives, “prosauropods.’ The sauropodomorphs were among the dominant herbivores of many terrestrial ecosystems, ranging from the early Late Triassic through the close of the Mesozoic. Although the basal sauropodomorph remains are scarce in North America, they are a globally widespread paraphyletic assemblage of terrestrial dinosaurs from the Late Triassic and

Early Jurassic. They were smaller than sauropods and were often able to walk on two legs. Basal sauropodomorphs exhibited a variety of sizes, ranging from 1.5–15 m in length depending on the species. Sauropodomorphs were adapted to browsing higher than any other contemporary herbivore, giving them access to high tree foliage.

Fossil remains of basal sauropodomorphs have been discovered on every continent and have provided insight into the possible lifestyles and habits of these animals. Possibly the most basal of the sauropodomorphs have been found in South

America, which has proven to be a particularly fossiliferous region for this clade. Langer et al. (1999) described Saturnalia, a 1.5 m long, gracile herbivore, based on the holotype and two paratypes initially. A second Triassic dinosaur from Brazil is Guaibasaurus, originally described by Bonaparte et al. (1999) as a basal theropod and the founding member of the family Guaibasauridae. After further consideration and comparison to

Saturnalia, Bonaparte et al. (date) reclassified Guaibasaurus as a basal sauropodomorph

(2007). Bonaparte believed Guaibasauridae could include Saturnalia and Ezcurra (2010) placed the subfamily Saturnaliinae within it. This subfamily includes Saturnalia, as well

Texas Tech University, Joshua Sundgren, May 2021 as Chromogisaurus, described by Ezcurra (2010), Panphagia (Martinez and Alcober,

2009), and later Pampadromaeus (Cabreira et al., 2011). All three of these sauropodomorphs were discovered in South America, with the former two being found in the fossiliferous Ischigualasto Formation of northwestern Argentina, which is Carnian in age (Late Triassic). The third, Pampadromaeus, was discovered in southern Brazil at Rio

Grande do Sul within the Santa Maria Formation, which is also Carnian in age.

However, later analysis has cast doubt on the classification of Guaibasaurus as a sauropodomorph. Langer et al. (2018), in a paper that included a phylogenetic analysis of many of the Late Triassic dinosaurs mentioned here, contended that Guaibasaurus is indeed a basal theropod as originally thought. In light of this, the subfamily Saturnaliinae was renamed as the family Saturnaliidae with the same membership described previously.

The contention over the placement of Guaibasaurus within the large clade Saurischia, or lizard-hipped dinosaurs, is reflective of the close relation of Theropoda and

Sauropodomorpha as the primary constituents of the larger clade. This proximity was illustrated further with the discovery of the basal sauropodomorph Buriolestes, another species from the Santa Maria Formation, which possessed teeth that were curved and serrated (Cabreira et al., 2018). This is indicative of a carnivorous lifestyle unlike more derived sauropodomorphs. Müller and Garcia (2019) placed Buriolestes at the base of

Sauropodomorpha in their phylogeny. Müller and Garcia (2019) also considered the Late

Triassic Eoraptor (Sereno et al., 1993) to be a sauropodomorph and that it was likely omnivorous based on its heterodont dentition. Another prominent sauropodomorph from the Santa Maria Formation is Bagualosaurus (Pretto, Langer, and Schultz, 2018), which was slightly larger than some of the other species from the region at approximately 2.5 m

Texas Tech University, Joshua Sundgren, May 2021 in length and shared some skull and dentition characteristics with more derived sauropodomorphs that occurred later in the Triassic.

Sauropodomorphs began to radiate out of the region that would become South

America and by the Norian Age of the Triassic, species spread into present-day India,

Africa and Europe, while continuing to diversify in South America. One particularly prominent taxon of sauropodomorph from Europe is Plateosaurus (von Meyer, 1837).

Plateosaurus is an important member of the sauropodomorphs as it serves as the founding member for the clade Plateosauria, which includes the family Plateosauridae and the secondary clade Massopoda, as well as the outlier species from Germany,

Ruehleia (Galton, 2001). A number of other basal sauropodomorphs have also been found in Europe, including Pantydraco (Galton, Yates, and Kermack, 2007),

Thecodontosaurus (Morris, 1843), and Efraasia (von Huene, 1907–1908). Many of these outlying taxa are grouped together in the clade Bagualosauria (Müller, 2019), which sits near the base of the clade Sauropodomorpha.

Two sauropodomorph genera were discovered in the Upper Maleri Formation of

India, which dates to the late Norian – early Rhaetian (Novas et al., 2011). One of these genera was Nambalia, which is another bagualosaurid. The other sauropodomorph genus found was Jaklapallisaurus, which is a member of a family of sauropodomorphs known as unayasaurids. Unaysauridae was established by Müller et al. (2018) in the description of the new genus Macrocollum, from the Candelária Sequence of Brazil. The description of Macrocollum included some notable characteristics, such as the animal’s neck being proportionally two times longer than that of the most basal sauropodomorph Buriolestes, indicating that the elongated necks which would become the hallmark of derived

Texas Tech University, Joshua Sundgren, May 2021 sauropodomorphs developed relatively early in the Mesozoic. Additionally, there were a total of three distinct specimens found together in the Candelária Sequence, which Müller notes is the oldest evidence of gregarious behavior among sauropodomorphs. The namesake of Unaysauridae, Unaysaurus, was also found in Brazil in the Catarrita

Formation, which overlies the Santa Maria Formation from where several basal sauropodomorphs were discovered, such as Saturnalia (Darosa et al., 2004).

India has produced other basal sauropodomorphs in addition to Nambalia and

Jaklapallisaurus, three of which were described by Kutty et al. (2007). These taxa,

Pradhania, Lamplughsaura, and an indeterminate taxa referred to as ISI R260 were discovered in the Lower Jurassic (Sinemurian) Upper Dharmaram Formation. Although they are known to fall within the clade Sauropodomorpha, the exact phylogenetic position of these three taxa is unclear. After running the characteristics of the taxa through multiple phylogenies, the results indicate more favorably that Lamplughsaura may actually be a basal sauropod, though it could still be a basal non-sauropod sauropodomorph, whereas Pradhania is more derived than Saturnalia and

Thecodontosaurus but appears to sit outside the combined clade of Sauropoda +

Plateosauria. The remains of ISI R260 are too fragmentary to say with certainty where the animal lies phylogenetically beyond being more derived than Saturnalia and

Thecodontosaurus.

Another part of the world which has produced significant remains of the earliest dinosaurs is the Elliot Formation of South Africa. These rocks date are Late Triassic and the Early Jurassic in age, and bear a rich assemblage of fossils from this time period, including several basal sauropodomorphs. McPhee et al. (2017) recounted the array of

Texas Tech University, Joshua Sundgren, May 2021 sauropodomorphs that have been found in both the Triassic and the Jurassic sections of the Elliot Formation, noting that both the diversity and the completeness of the assemblage is greater in the Jurassic sediments than the Triassic sediments. One issue with the sauropodomorph assemblage of the Triassic Elliot Formation is the taxon

Euskelosaurus (Huxley, 1866), which has recently been considered a nomen dubium to which material from multiple unique taxa has likely been assigned. What is now referred to as the Lower Elliot Formation zone was for a period of time labeled the

“Euskelosaurus range zone”, while the Upper Elliot Formation zone was formerly the

“Massospondylus range zone” (Kitching and Raath, 1984). In a series of papers, (Yates,

2003, 2007; Yates et al., 2004; Yates and Kitching, 2003), Yates made a convincing argument that there are in fact five valid sauropodomorph genera from the Lower Elliot

Formation. These genera include Plateosauravus, Eucnemesaurus, Blikanasaurus,

Melanorosaurus, and Antetonitrus. Plateosauravus was suggested by Yates (date) to take the place of “Euskelosaurus” and it is believed to be a valid basal sauropodomorph.

Eucnemesaurus was assigned by Yates (2007) to the newly formed family Riojasauridae along with the namesake of the group, Riojasaurus (Bonaparte, 1969), another sauropodomorph from the Ischigualasto Formation of Argentina. Both of these taxa are believed to be particularly bulky, more so than other contemporary sauropodomorphs.

Phylogenetically, Riojasauridae is thought to be near the divergence point of the true sauropods. Blikanasaurus and Melanorosaurus have at times been considered basal sauropods themselves and this still holds true for Blikanasaurus. Melanorosaurus is now classified in its own family, Melanorosauridae, just outside of the true sauropods.

Texas Tech University, Joshua Sundgren, May 2021

However, this is still an area of confusion due to a lack of material and these classifications could change with future discoveries.

As previously mentioned, the Early Jurassic Upper Elliot Formation zone was once known as the “Massospondylus range zone”, named for one of the most prominent genera of basal sauropodomorphs found there. Unlike Euskelosaurus, though,

Massospondylus is recognized as a legitimate taxon and is one of the oldest dinosaurs to be named, having been discovered and described by Sir Richard Owen in 1854. Material has been found around Africa, as well as India, and was reported from Arizona and

Argentina, though this material has since been assigned to other taxa. Reisz et al. (2005) described an articulated embryo of Massospondylus from the Elliot Formation and concluded that hatchlings of this dinosaur may have required parental care.

Massospondylus has laid the foundation for its own family Massospondylidae, and clade

Massopoda, which itself falls within the clade Plateosauria. Massospondylidae contains a number of significant basal sauropodomorphs, including the Lufeng taxa Xingxiulong and

Lufengosaurus, as well as possibly Pradhania and another taxon from Argentina,

Coloradisaurus. Another member of Massospondylidae is Glacialisaurus from the Early

Jurassic Hanson Formation of Antarctica, which indicates the group had adapted to the freezing conditions of the polar region (Smith and Pol, 2007). The clade Massopoda is of particular significance to this paper, as Jingshanosaurus is a member along with another

Lufeng sauropodomorph Yunnanosaurus and the family Riojasauridae. These taxa are among the most derived sauropodomorphs that are not considered true sauropods.

Phylogenetically, Sauropodiformes is the next major group following Massopoda, and this clade includes sauropods.

Texas Tech University, Joshua Sundgren, May 2021

The more derived clade of sauropodomorphs, the true sauropods, generally grew to very large size, were quadrupedal, and became the largest animals to ever walk the

Earth. They reached sizes up to 40 m in length, 17 m in height and had body masses as high as 100 metric tons (Sander and Clauss, 2008). Coincidentally, the sauropods at the highest end of these size ranges, the massive titanosaurs, are frequently found in South

America, the same continent in which many of the smallest and oldest sauropodomorphs have also been found. Sauropods were an extremely successful clade of dinosaurs, surviving for 160 million years and evolving over 120 different species (Dodson and

Dawson, 1992; Upchurch et al., 2004). The success of sauropods is all the more impressive considering they possess anatomical qualities that to some may appear disadvantageous. These include small heads, simple teeth and small and archaic brain architectures. The brain-to-body size ratio of sauropods, also referred to as the encephalization quotient, is 0.2, the smallest of any type of dinosaur.

There has been a lengthy debate about the relationship of “prosauropods” to

Sauropoda, as some contend they form a monophyletic sister-group (Wilson and Sereno,

1998; Sereno, 1999; Galton, 1999; Galton and Upchurch, 2000; Novas, 1996), while others say they are a paraphyletic group (Gauthier, 1986; Benton et al., 2000; Yates,

2003, 2005; Yates et al., 2004; Yates and Kitching, 2003; Galton and Upchurch, 2004;

Leal et al., 2004; Pol and Powell, 2005; Upchurch et al., 2007). There is now a general consensus that “prosauropods” are paraphyletic to Sauropoda, but some postulate that the more derived prosauropod taxa such as Coloradisaurus, Plateosaurus, Riojasaurus,

Lufengosaurus, Massospondylus, Yunnanosaurus, and possibly Jingshanosaurus form the clade Plateosauria, a sister-group to Sauropoda (Upchurch, 1998; Upchurch et al.,

Texas Tech University, Joshua Sundgren, May 2021

2007). In this new realignment, basal sauropodomorphs such as Saturnalia,

Thecodontosaurus, and Efraasia may be a paraphyletic assemblage that lies basal to plateosaur + sauropod divergence. Plateosaurs (sensu Upchurch et al., 2007) achieved a near global distribution during the Triassic-Jurassic transition and are crucial to understanding the evolution of the sauropod body plan. Additionally, this paper recognizes the informality of the term “prosauropod” and any use of the word in this paper should be considered equivalent to basal sauropodomorph.

Sauropodomorph skeletal material is most often found in fluvial settings.

Although discoveries of sauropodomorph bones have become more common, many such finds still lack important cranial and vertebral column elements. This is largely because the articulation of the small, fragile head and the neck vertebrae is weak and breaks down quickly, leading to frequent separation of these parts of the body from the rest of the skeleton by the action of water or scavengers. Furthermore, because the skull and neck vertebrae are smaller and more fragile, they are more prone to complete disintegration after disarticulation. The rest of the body, particularly the limbs and larger vertebrae, are more robust and more frequently preserved. As a result, most basal sauropodomorphs are diagnosed on the basis of their appendicular elements, which is not always ideal for studying the evolution and speciation of these animals. Between closely related taxa, postcranial material is often similar whereas distinguishing characteristics may be more easily observed in skulls, making the lack of this material especially problematic for establishing the relationships of early sauropods. Currently, this is a very confusing and controversial area of dinosaur phylogeny (Wilson and Sereno, 1998; Upchurch, 1998;

Upchurch et al., 2007).

Texas Tech University, Joshua Sundgren, May 2021

Considering this situation, the Lufeng Formation of Yunnan Province China and the material that the region has yielded is extremely valuable to the study of the basal sauropods and early sauropodomorphs. The Lufeng Formation has provided abundant remains of sauropodomorphs, which range from isolated elements to complete, articulated skeletons (Young, 1951). Two genera of basal sauropodomorphs that are particularly common are Lufengosaurus (Young, 1941, Barrett et al., 2005) and

Yunnanosaurus (Young, 1942), though well-preserved cranial material has not been found for either of these taxa yet. Other sauropodomorph genera from Lufeng include

Jingshanosaurus and Xingxiulong, as well as Chuxiongosaurus, Xixiposaurus, and

Yizhousaurus, which may represent a basal sauropod. Remains of Jingshanosaurus that were nearly complete and included an intact skull have been found. However, that skull is also encrusted with ferruginous minerals, making an analysis of the features of the skull difficult (Zhang and Yang, 1994). Sauropodomorphs are present in all levels of

Mesozoic Chinese strata, from the early Jurassic onward into the Cretaceous, so it is crucial to understand the origins of these mighty herbivores.

1.1 MATERIALS AND METHODS

In this paper, we describe new skull material of Jingshanosaurus, coming from a specimen found in Unit 7 of the Zhangjia’ao Member of the Lufeng Formation. The skull material is lacking parts of the braincase but includes most of the remaining bones.

The specimen was collected by Sankar Chatterjee and his expedition team in 1985. Most of the postcranial material is still housed in the Institute of Vertebrate Paleontology and

Paleoanthropology (IVPP) but the skull material was loaned to us for study. The specimen will be analyzed and characters from the material will be added to a phylogeny,

Texas Tech University, Joshua Sundgren, May 2021 with the goal of gaining a better understanding both of the morphology of

Jingshanosaurus and of the early evolutionary history of sauropodomorphs. There will be a particular focus on the sauropodomorphs from Lufeng, including the aforementioned

Lufengosaurus, Yunnanosaurus, and Yizhousaurus.

1.2 INSTITUTIONAL ABBREVIATIONS

Chuxiong Prefectural Museum (CXM), Indian Statistical Institute (ISI), Institute of Vertebrate Paleontology and Paleoanthropology (IVPP), Bureau of Land and

Resources of Lufeng County (LFGT), Texas Tech University (TTU)

Texas Tech University, Joshua Sundgren, May 2021

CHAPTER 2

GEOLOGIC SETTING

The Jurassic Period extended from 210 Ma to 145 Ma and is divided into the

Early, Middle, and Late Jurassic epochs. A single landmass known as Pangaea covered approximately one third of the Earth, while the rest of the globe was covered with water.

The Early Jurassic was a period of geologic and biologic upheaval on a global scale. A global plate tectonic reorganization took place that signaled the end of Pangaea and the beginnings of the world’s modern ocean basins and continents. The first stage of this process saw Pangaea split into two smaller continents, Laurasia to the north and

Gondwanaland to the south, with the Tethys Sea, or Neotethys, partially separating them.

At that time, China was a collage of small continental blocks that were separated by shallow seas (Figure 2.1). The early Jurassic Lufeng basin was located in the southern border of the South Block.

The Early Jurassic also saw shifts in the global climate. The preceding Triassic period had been a time of dry, arid conditions across Pangaea, but this changed as the

Jurassic Period began. The climate became more humid and combined with already warm temperatures, which allowed for the spread of forests and jungles across much of the land. These wooded areas were filled mostly by various types of gymnosperms, such as conifers, cycads, and ginkgoes, along with other types of plants such as ferns and horsetails. There is no environment today that is exactly like that of the Early Jurassic, although some forests in China still contain many of those same types of plants.

Ginkgoes have gone almost completely extinct, with the sole exception of Ginkgo biloba, which only grows naturally in tracts in the Dalou Mountains of southwestern China.

Texas Tech University, Joshua Sundgren, May 2021

Forests in New Zealand, such as Waipoua Forest, also contain large populations of ferns and conifers, and so could be somewhat representative of the Early Jurassic environment.

It has long been thought that the flowering angiosperms did not develop until during the

Early Cretaceous. However, recent fossil evidence from China has indicated that angiosperms had developed in the Early Jurassic. A fossil flower, Nanjinganthus dendrostyla, was found in the Early Jurassic-aged South Xiangshan Formation, near the city of Nanjing, and shows characteristics suggesting it bore enclosed seeds (Fu et al.

2018).

Figure 2.1 Earth in the Early Jurassic - Plate reconstruction for the Early Jurassic time showing the paleoposition of North and South China blocks. The Lufeng Basin (red circle) was located in the South China Block (after Scotese 2011). These were some of the biologic changes occurring in the Early Jurassic related to plants. In terms of faunal shifts, the planet was recovering from the Triassic-Jurassic extinction event, recognized as one of the traditional “Big Five” mass extinctions in

Earth’s history. This particular mass extinction wiped out many of the large amphibians

Texas Tech University, Joshua Sundgren, May 2021 and early reptiles, which fulfilled many of the predator and prey roles, or niches, in the environment. Dinosaurs were present during the Triassic but were not particularly widespread due to heavy competition and harsh conditions. The open niches left by the

Triassic-Jurassic extinction event, in conjunction with more hospitable environmental conditions, allowed for the proliferation of dinosaurs across Laurasia and Gondwanaland during the Jurassic, leading to the evolution of many well-known dinosaur groups such as sauropods and stegosaurids.

China during the Early Jurassic experienced the same warm, humid environmental conditions seen elsewhere during the time period. This led to prolific growth of plant life, primarily gymnosperms, with the possibility of some early angiosperms, creating an environment that could support many different organisms. The

Lower Jurassic Lufeng Formation in Yunnan Province of southwestern China provides one of the most abundant records of sauropodomorphs in the world. To date, seven genera of non-sauropodan sauropodomorphs have been reported from the Lufeng

Formation: Lufengosaurus, Yunnanosaurus, Jingshanosaurus, Chuxiongosaurus,

Xixiposaurus, Xingxiulong, and Yizhousaurus (Wang et al. 2020). This great diversity of sauropodomorphs may be due to the wide variety of plant life in the region, allowing different species to specialize what they fed upon. One of the interesting sauropodomophs present in China during the Early Jurassic is Jingshanosaurus xinwaensis. The skull material described here was found in the classical fossiliferous site of the Lufeng Basin (Chatterjee 2019). This area was on the southern boundary of

Laurasia, not far from the Tethys Sea, and was the location of rivers, lakes and floodplains. The high volume of water flowing through the land led to large amounts of

Texas Tech University, Joshua Sundgren, May 2021 sediment being left behind, creating the stratigraphy that we see today. The region also experienced widespread tectonic activity, with numerous faults and fractures leading to the generation of the disconnected basins, including the Lufeng Basin.

Simmons (1965) reviewed the stratigraphy, tectonic history, and fossil material of the Lufeng Basin. Some of the information presented in Simmons’s review has since been rendered outdated by later studies, particularly in regards to the dating of the regional stratigraphy. However, the information related to the tectonic history and makeup of the strata is still accurate. This area is a structural basin that was formed by the subsidence, or sinking, of the Central Yunnan Swell, also referred to as the Central

Yunnan Block. The Central Yunnan Swell had risen and subsided cyclically over the course of the Paleozoic Era, having been a recognizable tectonic structure since the late

Neoproterozoic Era. The most recent time relative to the Early Jurassic during which the

Swell had risen was the Permian, just before the beginning of the Mesozoic Era. As the

Permian came to a close and the Triassic began, the uplifted Swell served to block the rising Triassic sea in the south, along the Sino-Burmese geosyncline, a large scale depression for which geologic evidence has been found in China, Myanmar, Thailand and

Malaysia (Kobayashi, 1973). The Triassic sea instead went around the Swell to the east and west as two seaways travelling northward. During the Triassic, the area on the Swell, present-day central Yunnan Province, received only sediment from the land, with some minor mixing of terrestrial and marine deposits along the outer border of the Swell. The sedimentation that occurred in the Triassic was voluminous and led to the subsidence of the Swell by the Early Jurassic, which formed the Lufeng Basin.

Texas Tech University, Joshua Sundgren, May 2021

The strata in the Lufeng Basin consist of a set of Jurassic age, continental redbeds that form a sequence roughly 1 km. thick, referred to as the Lufeng Group (Figures 2.2,

2.3). The redbeds are made up of interconnected lacustrine, fluvial and flood plain deposits, but no marine deposits. These deposits consist of dark, purplish to red mudstones, with siltstones, sandstones and calcareous nodules inserted between the mudstone layers (Sun et al., 1985; Fang et al., 2000). Historically, the Lufeng Group has been divided into the Lower and Upper Lufeng Formations, differentiated by their lithology and fossil content (Bien, 1941). Recently, however, a change to this system was proposed by Fang et al. (2000). However, Fang et al. (2000) renamed the Lower

Figure 2.2 Lufeng, China - Locality map of China showing the location of Lufeng in the Southwest.

Lufeng Formation as simply the Lufeng Formation, and the Upper Lufeng Formation was broken into four distinct formations, which in descending order are the Anning Fm., the

Texas Tech University, Joshua Sundgren, May 2021

Madishan Fm., the Laohucan Fm., and the Chuanjie Fm. The rebranded Lufeng

Formation contains two members, the younger Zhangjia’ao Member and the older

Shawan Member (See Figure 2.4). These two names have appeared sporadically throughout literature pertaining to the Lufeng Basin strata, sometimes as formations themselves and other times as members, like in Fang’s classification. This revision has been accepted by some scientists, but not everyone and both classifications can be seen in the scientific literature published since the proposal was made. This paper will utilize

Fang’s classification.

One of the features often used to immediately differentiate the Zhangjia’ao

Member from the Shawan Member is color. The Shawan Member is a dull purple in color whereas the Zhangjia’ao Member is dark red, often called wine red by geologists.

The two members correlate to the Hettangian and the Sinemurian stages of the Early

Jurassic, respectively.

The Zhangjia’ao Member was described by Fang et al. (2000) as having a thickness of 164.5 m, though in the Shawan region of Lufeng, it is 202 m thick, as measured by the Yunnan Redbed Corps (1967). The unit is made up primarily of dark red and tan-red mudstones with some thinly laminated siltstones, as well as sandstones and conglomerates, interspersed between them. There are no disconformities between it and the underlying Shawan Member. Instead massive green sandstone layer separates them, which was described by Simmons (1965) as containing angular rock fragments derived from a Sinian (Ediacaran) source, becoming a breccia at outcrops in Yaochan.

There is a disconformity between the Zhangjia’ao Member and the overlying Chuanjie

Formation of the Middle Jurassic, which is made up predominantly of yellow sandy

Texas Tech University, Joshua Sundgren, May 2021 conglomerates. The fossil assemblage of the Zhangjia’ao Member includes the sauropodomorphs Yunnanosaurus, Yizhousaurus and Lufengosaurus. The Zhangjia’ao

Member has been biostratigraphically correlated with the Upper Dharamaram Formation of India and the Upper Elliot Formation of southern Africa, both of which preserve the remains of sauropodomorphs (Kutty et al. 2007).

Figure 2.3 Detailed Locality Map - Geographic position of the Lufeng Basin in the Yunnan Province of southwestern China showing the fossil localities (black circles) of sauropodomorphs around the village Lufeng.

The Shawan Member was described by Fang et al. (2000) as having a thickness of

107.7 m in the location he and his team measured, though it is much thicker, over 500 m, in the Lufeng Basin and the nearby Chuanjie Basin. The Shawan Member is made up predominantly of dark purple-red and dark purple mudstones, along with interbedded siltstones, shales and sandstones. There are calcareous nodules throughout and beds in

Texas Tech University, Joshua Sundgren, May 2021 the unit are penetrated by streaks and veins of calcite. The base of the Shawan Member contains large, 2-3 cm clasts. Simmons (1965) refers to it as a breccia, derived from the underlying rocks, whereas Fang et al. (2000) labels it a well-rounded conglomerate, tabularly bedded with argillaceous cement. It is possible that the base of the Shawan

Member varies in its composition from one outcrop to another, though a number of sources appear to favor the description of conglomerate. There is an unconformity between the Shawan Member and the underlying unit, the Etouguang Formation of the

Kunyang Group, which dates back to the Proterozoic and is made up of purple phyllites.

Among the vertebrate fauna preserved in the Shawan Member are the sauropodomorphs

Yunnanosaurus, Lufengosaurus, and Jingshanosaurus xinwaensis.

The sauropodomorphs mentioned thus far are part of a much larger group of prehistoric animals known as the Early Jurassic Lufeng Saurischian Fauna, a term first coined by Chinese paleontologist C.C. Young (1951). At the time of his description, there were 15 genera and 20 species that had been recorded and other specimens that had yet to be assigned. Thirty years later, Young (1982) conducted a second review of

Lufeng taxa, which increased those numbers to 22 genera and 27 species (Sun et al.,

1985). Although the term specifically mentions saurischians, the Lufeng Saurischian

Fauna is a broad and wide-ranging group, indicative of a diverse faunal assemblage and ecosystem during the Early Jurassic. In addition to the sauropodomorphs, the Lufeng

Saurischian Fauna includes turtles, pseudosuchians (crocodiles and their relatives), saurischian dinosaurs besides the sauropodomorphs, ornithischian dinosaurs, therapsids and early mammals, to name some of the more prominent examples. Sun et al. (1985) provided a much more detailed, if now dated, review of the Lufeng Saurischian Fauna.

Texas Tech University, Joshua Sundgren, May 2021

Figure 2.4 Stratigraphy Column - Stratigraphic section of the Lower Lufeng Formation showing two lithostratigraphic units: the lower Shawan Member (lower Dull Purplish Beds) and the Zhangjia’ao Member (upper Dark Red Beds). Jinshanosaurus fossils were recovered from the topmost sequence of the Zhangjia’ao Member.

Today, the area around Lufeng is home to the Lufeng World Dinosaur Valley, near Ana Village about 80 km from Yunnan Province’s capital, Kunming. The Lufeng

World Dinosaur Valley was established in 2008, accompanying the Lufeng Dinosaur

Museum, which was founded in 1990, and it consists of three main parts, the Lufeng

Dinosaur Relics Hall, the Science Exploration Site, and the Jurassic World. Recognizing the cultural value and historic significance of the Lufeng strata and the fauna preserved within, the People’s Government of Lufeng County and Chinese paleontologists worked together to construct the Dinosaur Museum and the World Dinosaur Valley to celebrate

Texas Tech University, Joshua Sundgren, May 2021 and preserve Lufeng’s prehistoric past, educate visitors, and maintain the region’s status as one of the world’s foremost sources for Jurassic fossils.

Texas Tech University, Joshua Sundgren, May 2021

CHAPTER 3

PREVIOUS WORK

Nine genera of sauropodomorphs are currently known from the Lufeng Basin and surrounding area (Zhang et al. 2020; Fabrégues et al., 2020): “Gyposaurus” sinensis

(Young, 1941), Lufengosaurus (Young, 1941), Yunnanosaurus (Young, 1942),

Jingshanosaurus (Zhang & Yang, 1994), Chuxiongosaurus (Lü et al, 2010), Xixiposaurus

(Sekiya, 2010), Xingxiulong (Wang et al. 2017), Yizhousaurus (Zhang et al., 2018) and the most recently described Irisosaurus (Fabrégues et al., 2020). The focus of this project is Jingshanosaurus, but it is important to understand the relations of this animal to the other sauropodomorphs from the region. Following is a review of these other sauropodomorphs and what is currently known about them.

3.1 “GYPOSAURUS” SINENSIS

“Gyposaurus” sinensis, Yang, 1940 Lufengosaurus huenei, Galton, 1976 Anchisaurus sinensis, Dong, 1992 “Gyposaurus” sinensis, Galton and Upchurch, 2004 Lufengosaurus huenei, Wang et al., 2017

Holotype – Partial skeleton including maxilla, neck vertebra, left and right humerus, left and right scapula and coracoid, left radius, astragalus, femur, ulna, hand, tibia, fibula

(IVPP V26) from Lufeng Co., Yunnan Province, China; anterior caudal vertebra (IVPP

V27) from Lufeng Co., Yunnan Province, China.

Remarks – One of the two earliest described sauropodomorphs from Lufeng,

“Gyposaurus” sinensis has a complicated taxonomic history and may not even be a valid taxon. Another species, “Gyposaurus” capensis was described earlier than “G.” sinensis based on material from the former Orange Free State (now the Free State province) of

Texas Tech University, Joshua Sundgren, May 2021

South Africa (Broom, 1911). Since the initial description of “G.” capensis, the material has been synonymized to Massospondylus (Cooper, 1981). “G.” sinensis was described by Chinese paleontologist Yang Zhongjian, also known as C.C. Young in 1940 based on a specimen of a partial skull and skeleton. The material has been referred to multiple other sauropodomorphs over time, though more recently, “G.” sinensis was considered to possibly be a valid taxon by Galton and Upchurch (2004). However, at the 2017 Society of Vertebrate Paleontology conference, Wang and colleagues proposed again that the holotype is actually a specimen of Lufengosaurus huenei, specifically a juvenile (Wang et al., 2017). They note that the dorsal vertebrae are unfused and that the bone histology of the fibula is more typical of a young individual. Numerous skeletal similarities between

“G.” sinensis and L. huenei are described and a phylogeny in which the two species are separate places them both in a polytomy along with the sauropodomorphs Glacialisaurus and Coloradisaurus. The presentation focused only on the holotype and other specimens, including IVPP V43, V45, and V95, are noted by the authors as requiring further investigation. At present, the validity of “G.” sinensis as a taxon is still in question.

3.2 LUFENGOSAURUS

Dinosauria, Owen, 1842 Saurischia, Seeley, 1888 Sauropodomorpha, von Huene, 1932 Lufengosaurus, Young, 1941 (Figs. 1-6)

Type Species – Lufengosaurus huenei Young, 1941

Holotype – Complete skeleton with skull (IVPP V15)

Remarks – Lufengosaurus huenei is the other of the two earliest described basal sauropodomorphs from the Lufeng Basin, though it is less controversial than its

Texas Tech University, Joshua Sundgren, May 2021 contemporary, “Gyposaurus” sinensis. Since its initial description by Young (1941), some researchers have synonymized L. huenei with Yunnanosaurus huangi

(Rozhdestvensky, 1965) and Massospondylus huenei (Cooper, 1981), separate but closely related to the South African Massospondylus carinatus (Owen, 1854). However, a redescription of the holotype skull by Barrett et al. (2005) firmly established L. huenei as a distinct taxon. Four cranial autapomorphies, bony bosses on the ascending process of the maxilla, the jugal, and rostrolateral wing of the parietal, as well as a ridge on the lateral surface of the maxilla, were enumerated in the redescription and craniodental evidence was used to differentiate L. huenei from both Y. huangi and M. huenei. Several cranial features distinguish L. huenei from Jingshanosaurus xinwaensis, including the presence of “medial laminae” in the caudoventral corner of the ascending process of the maxilla and on the lachrymal, and its dentition, which lack the strong recurvature observed in J. xinwaensis.

A second species was referred to Lufengosaurus, L. magnus, by Young (1947). L. magnus is often regarded as a junior synonym to the type species, L. huenei

(Rozhdestvensky, 1965). However, it is still considered to be a possibly valid taxon and is treated as such in Mao et al. (2020), which utilizes new techniques to assess the biomass of the Early to Mid-Jurassic Lufeng Basin area. The primary difference between

L. huenei and L. magnus is their respective size; L. huenei measures approximately 6 m

(20 ft.) in length whereas L. magnus is larger, approximately 9 m (30 ft.), hence the name, magnus.

Numerous significant discoveries of Lufengosaurus material have been made over time, giving researchers important insight into the genus. Reisz et al. (2020) published a

Texas Tech University, Joshua Sundgren, May 2021 study concerning the development of teeth in multiple Lufengosaurus embryos and the broader implications for tooth development across the sauropodomorphs, including the true sauropods. They observed that embryonic Lufengosaurus individuals went through multiple cycles of tooth development without root resorption (the dissolving of teeth by the body), which the authors note is different from the dentition of hatchling and adult

Lufengosaurus. However, it is similar to the dental condition seen in adult sauropods such as diplodocids and titanosaurids, indicating these animals may have evolved their dentition through paedomorphosis.

Another important find was made in 2017 with the discovery of a collagen protein in the rib of a Lufengosaurus specimen (Lee et al. 2017). The results of their research are significant for multiple reasons. The studied material dates to approximately 195 million years ago, making the protein within over 100 million years older than the next oldest similarly preserved protein, at 75 million years. It is also significant because of the primary technique utilized during the study: SR-FTIR microspectroscopy is an analysis method which identifies vibrational motions of chemical bonding between molecular structures based on their characteristic infrared bands without causing any damage to the molecules themselves. This technique allowed the collagen protein to remain in situ and the authors believe that SR-FTIR microspectroscopy has the potential to be used for finding additional organic material in other fossils which are even older.

3.3 YUNNANOSAURUS

Dinosauria, Owen, 1842 Saurischia, Seeley, 1887 Sauropodomorpha, von Huene, 1932 Sauropodiformes, Sereno, 2007 Yunnanosaurus, Young, 1942

Texas Tech University, Joshua Sundgren, May 2021

Type Species – Yunnanosaurus huangi, 1942

Holotype – Near complete skeleton consisting of skull, atlas, axis; three cervical vertebrae; nine dorsal vertebrae, fragments of dorsal ribs; sacrum; eight caudal vertebrae, six haemal arches; left scapula; sternum; right and left humeri; right ulna; incomplete left manus, right and left ilia, pubes and ischia; right and left femora, tibiae, fibulae, astragali, and calcanea; two metatarsals (NGMJ 004546)

Remarks – Yunnanosaurus huangi was first described by Young (1942) with a diagnosis that included a number of cranial characteristics. However, many of the distinguishing characteristics used initially no longer differ from those of other basal sauropodomorphs.

Over time, Y. huangi has been considered synonymous with multiple other sauropodomorphs including Lufengosaurus huenei (Rozhdestvensky, 1965) and

Massospondylus huenei (Cooper, 1981). A recent cranial redescription by Barrett et al.

(2007) established a number of autapomorphies that clearly differentiate Y. huangi from those two taxa along with other basal sauropodomorphs. These autapomorphies include small external nares, a rostrocaudally expanded nasal process of the premaxilla, a lack of nutritive foramina on the lateral surface of the maxilla, midline bosses on both the rostral end of the frontals and the parietals, and mesiodistally narrow maxillary teeth that lack denticles. This final autapomorphy may no longer be such as the newly described

Irisosaurus also exhibits teeth with no denticles, but no other basal sauropodomorph has exhibited this condition. Even if the lack of denticles is no longer an autapomorphy of Y. huangi, there are still plenty of others that support the status of Y. huangi as a unique taxon.

Texas Tech University, Joshua Sundgren, May 2021

Another species, Y. robustus, was described by Young (1951), though this species has often been considered synonymous with either the type species, Y. huangi (e.g.

Galton, 1990; Galton and Upchurch, 2004) or Lufengosaurus huenei (e.g.

Rozhdestvensky, 1965). More recently, a specimen described by Sekiya et al. (2014) was assigned by them to Y. robustus. This specimen consists of some cranial material and a near-complete post-cranial skeleton (ZMNH-M8739), and based on an unfused neural arch and finely grooved long bone surface texture, is believed to be a juvenile. ZMNH-

M8739 possesses tooth-tooth wear facets on the mesial maxillary and dentary teeth, as well as coarse serrations on the distal maxillary teeth, suggesting a potentially unique feeding mechanism for the animal. Comparisons with adult Y. huangi specimens indicate distinct growth changes in Y. robustus, though the ultimate validity of Y. robustus as a distinct taxon is still uncertain.

A third species, Y. youngi, named in honor of C.C. Young, was described by Lü et al. (2007), who noted several distinct characteristics that differentiated Y. youngi from Y. huangi: an anteroposterior and dorsoventral expansion of the distal ends of the sacral ribs, forming a sacrocostal yoke that contacts the inner surface of the ilium and an ischium that is longer than the pubis. Additionally, Y. youngi is approximately 13 m long, almost twice as long as Y. huangi at 7 m in length.

Recent cladistics analyses have placed Yunnanosaurus as part of the clade

Massopoda. Novas et al. (2011) grouped Yunnanosaurus together with Anchisaurus and the subject of this research, Jingshanosaurus, in a clade within Massopoda. Further analyses have supported this position with minimal variation (Apaldetti et al., 2011;

Texas Tech University, Joshua Sundgren, May 2021

Müller et al., 2019), though some suggest that Yunnanosaurus is more basal than

Jingshanosaurus and Anchisaurus (McPhee et al., 2014).

3.4 CHUXIONGOSAURUS

Dinosauria, Owen, 1842 Saurischia, Seeley, 1887 Sauropodomorpha, von Huene, 1932 Chuxiongosaurus, Lü et al., 2010

Type species – Chuxiongosaurus lufengensis, Lü et al., 2010

Holotype – Nearly complete skull with lower jaw (CXM-LT9401)

Remarks – Chuxiongosaurus is one of the most controversial taxa from the Lufeng area.

It was diagnosed based on a single, nearly complete skull from the Lufeng Formation near Zhongcun Town, Yunnan Province. The specimen is small, only 34 cm in length, and was noted by the authors for being shorter and higher than other sauropodomorphs from the region, such as Lufengosaurus and Jingshanosaurus, in addition to showing morphological differences from the American genus, Anchisaurus. The authors concluded that, based on the morphology of the skull, the material is from a subadult member of the species and that Chuxiongosaurus likely represents the most basal true sauropod from the region, still sharing some characteristics with basal “prosauropods”, or sauropodomorphs.

However, a recent cranial redescription of Jingshanosaurus xinwaensis has cast doubt on the validity of C. lufengensis (Zhang et al., 2019). This study reexamined both the holotype specimen of J. xinwaensis, LFGT-ZLJ0113, in addition to the holotype of C. lufengensis, CXM-LT9401, as the authors noted that the latter specimen had been previously described by Wang (2004) and assigned to J. xinwaensis before the

Texas Tech University, Joshua Sundgren, May 2021 description of Chuxiongosaurus in 2010. In the redescription of CXM-LT9401, the authors agreed with the original assessment by Wang, referring the material to J. xinwaensis and considering C. lufengensis to be a junior synonym of the older animal.

Further research and material is required to determine whether C. lufengensis could be a valid taxon.

3.5 XIXIPOSAURUS

Dinosauria, Owen, 1842 Saurischia, Seeley, 1887 Sauropodomorpha, von Huene, 1932 Xixiposaurus, Sekiya, 2010

Type Species – Xixiposaurus suni, Sekiya, 2010

Holotype – Nearly complete skull with lower jaw, atlas; partial coracoid; partial right scapula, right ilium, pubis, ischium, humerus, femur, tibia, fibula, astragalus, distal tarsals, & metatarsals; partial left humerus, left ulna and radius; 8 cervical vertebrae, 12 dorsal vertebrae, 5 articulated caudal vertebrae (ZLJ0108)

Remarks – The material for this taxon was discovered in the Lower Lufeng Group. The animal was described as a plateosaurid by Sekiya (2010) and was placed as a sister taxon to Plateosauria in the cladogram constructed for the article. This cladogram also places

Jingshanosaurus xinwaensis as a sister taxon to Sauropoda, which is a problematic placement that does not agree with much of the other literature regarding basal sauropodomorphs.

3.6 XINGXIULONG

Dinosauria, Owen, 1842 Saurischia, Seeley, 1887 Sauropodomorpha, von Huene, 1932 28

Texas Tech University, Joshua Sundgren, May 2021

Massopoda, Yates, 2007 Sauropodiformes, Sereno, 2007 (sensu) Xingxiulong, Wang et al., 2017

Type Species – Xingxiulong chengi, Wang et al., 2017

Holotype – Partial skull and mandible; post-cranial skeleton including atlas-axis complex, three cervical vertebrae, seven dorsal vertebrae, complete sacral vertebral series, 35 caudal vertebrae, rib and chevron fragments, left ilium, left pubic apron and distal end of right pubis, proximal end of left ischium and distal portions of articulated ischia, both femora, both broken tibiae and proximal ends of fibulae, left astragalus and calcaneum, putative distal tarsals III and IV, and complete left pes and near-complete right pes

(LFGT-D0002)

Remarks – X. chengi is another recently described taxon from Lufeng that possesses an interesting combination of basal and derived sauropodomorph characteristics. In the phylogenetic analysis conducted by Wang et al. (2017), the animal was found to be a basal sauropodiform of the clade Massopoda, and a sister-taxon to Jingshanosaurus xinwaensis. This conclusion is supported by five synapomorphies shared by the two taxa: the anterior margin of the infratemporal fenestra placed behind the orbit, width of the scapula greater than 20% of its length, concave lateral margin of the pubic apron, anteroposterior expansion of the distal pubis greater than 15% of the total length, and an approximate 30 degree angle between the long axis of the femoral head and the transverse axis of the distal femur.

Although many of the physical characteristics indicate a close relationship to other basal sauropodomorphs (i.e. J. xinwaensis), Wang et al. (2017) noted several features of X. chengi that are more commonly associated with true sauropods. One such

Texas Tech University, Joshua Sundgren, May 2021 feature is a sacrum composed of four sacral vertebrae: a dorsosacral vertebra, two primordial sacral vertebrae, and a caudosacral vertebra, as opposed to the three sacral vertebrae seen in other basal sauropodomorphs, including those from Lufeng. Another feature observed in X. chengi is a pubic plate that is approximately 40% of the total length of the pubis. Many basal sauropodomorphs possess a pubic plate that makes up only about 25% of the pubis, as opposed to approximately 33% of the total length in many sauropods and up to 45-50% in camarasauromorph sauropods. Additional physical characteristics were listed that differ from those frequently observed in basal sauropodomorphs, but that do not necessarily overlap with those seen in sauropods.

Wang et al. (2020) provided an in-depth analysis of the axial skeleton (skull and vertebral column) of X. chengi, drawing much of their description from one of the paratypes, LFGT-D0003, discovered along with the holotype, LFGT-D0002, as its cranial material is better preserved. Their findings indicated the skull of X. chengi is more similar to that of other basal sauropodomorphs than to true sauropods, but that the postcranial skeleton preserves some unusual features. These include the aforementioned four vertebrae sacrum but also caudal dorsal vertebrae with laterally expanded neural spine tables.

3.7 YIZHOUSAURUS

Dinosauria, Owen, 1842 Saurischia, Seeley, 1887 Sauropodomorpha, von Huene, 1932 Massopoda, Yates, 2007 Sauropodiformes, Sereno, 2007 (sensu) Yizhousaurus, Zhang et al., 2018

Type Species: Yizhousaurus sunae, Zhang et al., 2018

Texas Tech University, Joshua Sundgren, May 2021

Holotype: An undistorted skeleton including well-preserved skull with mandible; mostly complete vertebral series including 9 cervicals, 14 dorsals, 3 sacrals, and 5 anterior caudals; pectoral and pelvic girdles, forelimbs (lacking both carpi) and both femora

(LFGT-ZLJ0033).

Remarks: Yizhousaurus was the most recent sauropodomorphs from the Lufeng area to be described prior to the description of Irisosaurus (see below) and the material upon which the description is based is in excellent condition. The authors note a unique combination of plesiomorphic and apomorphic characters that distinguish Y. sunae from other non- sauropodan sauropodomorphs, particularly those from the surrounding region. The phylogenetic analysis conducted by Zhang et al. (2018) placed Y. sunae in

Sauropodiformes, as it possesses cranial characteristics that appear sauropodan in nature, while also exhibiting a plesiomorphic postcranial skeleton. The cranial characteristics noted include reductions of the antorbital and external mandibular fenestrae and the presence of lateral plates on the upper jaws. However, the authors refrained from labeling these similarities as apomorphies shared with true sauropods, acknowledging the possibility they could be instances of homoplastic convergence, in which two or more animals share traits that were not inherited from a common ancestor. One of the challenges in conducting a phylogenetic noted by the authors is the lack of good quality cranial material for many non-sauropodan sauropodomorphs, so an alternative cladistics analysis was carried out that focused exclusively on cranial characteristics and excluded any taxa without preserved skull material. This secondary analysis resulted in large polytomies, internal nodes of a cladogram with more than two immediate descendants,

Texas Tech University, Joshua Sundgren, May 2021 and left the affinities of many non-sauropodan sauropodomorphs unsolved, including Y. sunae. Ultimately, the need for more cranial material was reinforced.

The skull of Y. sunae is distinguished from those of the four uncontroversial

Lufeng sauropodomorphs: Lufengosaurus, Yunnanosaurus, Jingshanosaurus, and

Xingxiulong, through a number of different characteristics. The autapomorphies described by Zhang et al. (2018) distinguish Y. sunae from Lufengosaurus,

Yunnanosaurus, and Xingxiulong. Jingshanosaurus is noted for having a number of indistinct morphological characteristics believed to be diagnostic and that some of the cranial features are incorrectly coded in the phylogenetic analysis due to a poorly restored skull roof. However, Y. sunae is still distinguishable from Jingshanosaurus because of the following characteristics: the presence of the lateral plates on the upper jaw, a subtriangular antorbital fenestra in Jingshanosaurus which is larger than that of Y. sunae, the posterior margin of the middle dorsal neural spines are straight in lateral view in

Jingshanosaurus but concave in Y. sunae, the ischial peduncle of the ilium of Y. sunae has a projecting “heel” which Jingshanosaurus does not exhibit and postacetabular process of the ilium is different in the two animals.

3.8 IRISOSAURUS

Dinosauria, Owen, 1842 Saurischia, Seeley, 1887 Sauropodomorpha, von Huene, 1932 Massopoda, Yates, 2007 Sauropodiformes, Sereno, 2007 Irisosaurus, Fabrégues et al., 2020

Type Species: Irisosaurus yimenensis, Fabrégues et al., 2020

Texas Tech University, Joshua Sundgren, May 2021

Holotype: An associated partial skeleton including partial left maxilla and right dentary with three isolated teeth; five partial cervical vertebrae, three partial dorsal vertebrae, and a dozen vertebral fragments; over fifty dorsal rib fragments; near-complete right scapulocoracoid and partial left one; near-complete right humerus and partial left one; near-complete right ulna and partial left one; complete right radius and partial left one; two partial manus with carpals; two distal ends of ischia; one partial pes ungula phalanx and several unidentifiable fragments (CVEB-21901).

Remarks: As of this writing, Irisosaurus is the most recently discovered and described non-sauropodomorph from southern China. The recovered material was not actually found in the Lufeng Formation unlike the other sauropodomorphs discussed here, but it was instead discovered in the Fengjiahe Formation, a lateral equivalent to the Lufeng

Formation (Dong, 1992), which is also located within Yunnan Province.

Little of the skull is preserved in the holotype, which contains only a partial left maxilla, a partial right dentary, and three isolated teeth. The maxilla bears some similarities with that of Jingshanosaurus, but also some distinct differences. The premaxillary ramus bears only two small neurovascular foramina, while the posterior ramus bears none, which is unusual as most non-sauropodan sauropodomorphs, including

Jingshanosaurus, have a number of large neurovascular foramina. The premaxillary ramus is short and is expanded dorsoventrally relative to its anteroposterior development, which is in contrast to that of Jingshanosaurus, whose premaxillary ramus is longer than it is high. However, both Irisosaurus and Jingshanosaurus exhibit an elongate curved ridge on the premaxillary ramus which delimits the perinarial fossa.

Texas Tech University, Joshua Sundgren, May 2021

The three isolated teeth of Irisosaurus that were discovered also bear some similarity to those of Jingshanosaurus. The teeth have spatulate crowns with convex labial surfaces and concave lingual surfaces, and are mesiodistally widest at mid-height of the crown, a condition also observed in Jingshanosaurus. Furthermore, the tooth enamel of both Irisosaurus and Jingshanosaurus is smooth at the base of the crown but wrinkled toward the apex of the tooth.

3.9 JINGSHANOSAURUS

Dinosauria, Owen, 1842 Saurischia, Seeley, 1887 Sauropodomorpha, von Huene, 1932 Massopoda, Yates, 2007 Sauropodiformes, Sereno, 2007 (sensu McPhee et al., 2014) Jingshanosaurus, Zhang & Yang, 1995

Type Species: Jingshanosaurus xinwaensis, Zhang & Yang, 1995

Holotype: A well-preserved skeleton consisting of a skull with mandibles, the atlas-axis complex, the third cervical vertebra, 14 dorsal vertebrae, 3 sacral vertebrae, 38 caudal vertebrae and a nearly complete appendicular skeleton (LFGT-ZLJ0113).

Remarks: Jingshanosaurus xinwaensis is the subject of this study and has proven difficult for researchers to place phylogenetically. Some recent phylogenetic studies have placed

Jingshanosaurus as more derived than Yunnanosaurus but less derived than sauropodomorphs such as Anchisaurus and Melanorosaurus (Wang et al., 2017; McPhee et al. 2017), while other studies consider it less derived than Lufengosaurus and

Yunnanosaurus (Chapelle and Choiniere, 2018). As mentioned in the cranium redescription by Zhang et al. (2019), the original description by Zhang & Yang (1995) had unclear photographs and diagnoses, resulting in the uncertainty over the phylogenetic

Texas Tech University, Joshua Sundgren, May 2021 position of Jingshanosaurus. The redescription covered both the holotype, LFGT-

ZLJ0113, and additional cranial material in the form of CXM-LT9401, which was originally reported by Wang (2004) as Jingshanosaurus cf. xinwaensis and was then reported as a new species, Chuxiongosaurus lufengensis, by Lü et al. (2010). Zhang et al.

(2019) find that CXM-LT9401 is anatomically similar to LFGT-ZLJ0113 and the two specimens form a sister group in the study’s cladistics analysis, leading them to believe that C. lufengensis is a junior synonym to J. xinwaensis. Their analysis includes 91 scored characters for LFGT-ZLJ0113 and 103 scored characters for CXM-LT9401.

Zhang et al. (2019) listed nine autapomorphies in their diagnosis of J. xinwaensis, including an inflection at the base of the dorsal premaxillary process: the caudal margin level of the external naris is caudal to the mid-length of the maxillary tooth row and the rostral margin of the antorbital fenestra; the lacrimal orbital margin has a slightly rostrodorsally sloping orientation; a ventrally constricted subtriangular orbit; a rostrocaudally shortened jugal plate at suborbital region; the floor shape of the braincase in lateral view is bent with the basal tubera below the level of the basioccipital and the parasphenoid rostrum is raised above it; the dentary has a height-to-length ratio greater than 0.2; the length of retroarticular process is greater than the depth of the mandible below the glenoid; tooth crowns have a distally recurved long axis. In the phylogenetic analysis of the redescription, LFGT-ZLJ0113 and CXM-LT9401 were recovered as sister taxa to each other as previously mentioned, and J. xinwaensis was recovered as the second diverging clade of Sauripodiformes in between Xingxiulong and Yunnanosaurus.

Together, these three species represent the most basal members of Sauripodiformes.

However, other phylogenetic analyses have recovered other arrangements, such as

Texas Tech University, Joshua Sundgren, May 2021

Yunnanosaurus being more basal than Xingxiulong and J. xinwaensis, as well as

Lufengosaurus and Plateosaurus (Zhang et al., 2018). This illustrates the need for more study of Lufeng sauropodomorphs, including Jingshanosaurus in particular.

Texas Tech University, Joshua Sundgren, May 2021

CHAPTER 4

SKULL DESCRIPTION OF JINGSHANOSAURUS

4.1 GENERAL FEATURES

Although the cranial bones (IVPP-13246) are disarticulated, indicating that the individual was not fully adult, there is little sign of distortion. The isolated elements of the skull are three-dimensionally preserved. The skull elements include left and right premaxillae, left and right maxillae, left nasal, left prefrontal, left frontal, left postorbital, left vomer, left pterygoid, left ectopterygoid, left quadrate, left dentary, left surangular, and left articular. The estimated skull measurements of Jingshanosaurus from the complete skull (LFGT-ZLJ0113) are skull length 35 cm, skull width 16 cm, skull height

17.5 cm, and the length of the lower jaw 34 cm (Zhang et al., 2019). A composite restoration of the skull with the jaw in place of Jingshanosaurus of IVPP is shown below

(Figure 4.1). The skull exhibits long and narrow diplodocid design like other Lufeng sauropodomorphs.

Figure 4.1 Jingshanosaurus skull - Reconstruction of Jingshanosaurus skull, base diagram modified from Zhang et al. (2019). Bones colored dark grey and outlined with solid lines are preserved, while those with dotted outlines are absent. Pm, premaxilla; M, maxilla; N, nasal; Pf, prefrontal; F, frontal; Po, postorbital; P, parietal; S, squamosal; Q, quadrate; Qj, quadratojugal; J, jugal; D, dentary; Sa, surangular; A, angular; Ar, articular.

Texas Tech University, Joshua Sundgren, May 2021

4.2 DERMAL BONES OF THE SKULL ROOF 4.2.1 Premaxilla Both premaxillae are preserved; each shows the vertical median symphysis at the anterior end. The premaxilla is short and broad and has a curved ascending process that extends posterodorsally as a narrow process to contact the nasal; these two bones encircle the large, triangular external naris (Figures 4.2, 4.3). The nasal process is roughly triangular in lateral view, exceptionally thin in anterior view, and forms an approximate

45° angle with the main body. Ventral to the naris, the premaxilla has a broad contact with the maxilla, but the suture is interrupted by a small foramen. When viewed anteriorly, the transition from the nasal process to the anterior end of the main body is smooth and continuous. There is a little kink on the anterior margin of the premaxilla to form a rudimentary muzzle, which is well developed in later sauropods. The anterior end of the main body extends ventrally in front of the tooth row. The ventral tooth-bearing region of the premaxilla is somewhat quadrangular, thick, and robust. It has alveoli for four teeth though only three are preserved in either premaxilla; one alveolus is missing in the right one. The posterolateral process is thin and flat in medial view and canted slightly laterally. It extends from the dorsal edge of the main body and bears a prominent ridge extending along 75% of its dorsal surface. This process articulates with the flat, triangular depression on the dorsal surface of the anterior end of the maxilla. There is a small projection of bone just beneath the posterolateral process that, when combined with the ventral side of the process, creates a slot into which the anterior tip of maxilla projection fits. The right premaxilla is missing many of these elements, including all but the base of the nasal process, the posterolateral process, the ventrally projecting tip of the main body and much of the lateral outer surface of the main body. The right premaxilla

Texas Tech University, Joshua Sundgren, May 2021 has been split into two distinct portions, a dorsal part, which would typically possess the nasal process, and a ventral portion, which bears the teeth. The two portions are joined together at the posterior end of the premaxilla but are laterally offset from each other anteriorly by a distance of approximately 1.5 cm.

4.2.2 Maxilla

Both maxillae are preserved in good condition. The maxilla is a broad L-shaped bone and is divided into two major processes: a horizontal, tooth-bearing ramus and a posterodorsally projecting ascending process that separates the external naris from the antorbital fenestra. The antorbital fenestra is large, triangular, and somewhat narrower than the external naris. The anteroventral margin of the antorbital fossa is slightly concave, creating a narrow antorbital fossa. In lateral view, the ramus tapers posteriorly to contact the jugal, while the broad anterior end preserves a bony projection. This projection, approximately 3.3 cm in length, curves and angles slightly downward anteriorly, is flat on its dorsal surface and is roughly triangular in shape. It forms the articulation surface for the posterolateral process of the premaxilla and the entire anterior- most third of the ramus, up to the posterodorsal process, twists medially in order to better articulate with the premaxilla. The lateral surface of the ramus bears a varying number of nutrient foramina, ranging anywhere from five to ten on either bone. The posterodorsal process, preserved more fully on the right maxilla, forms an approximately 70° angle with the ramus to contact the lacrimal bar. The posterior face of the process has a deep sulcus that runs up at least half of the process and continues to the posterior end of the ramus's dorsal surface. The lateral surface of the ramus extends ventrally to form a thin lateral ridge, which serves as one margin of the sulcus and a low ridge projecting from

Texas Tech University, Joshua Sundgren, May 2021 the dorsal surface of the ramus forms the other margin. The posterior end of the ramus also bears a thin triangular flange, which projects medially at an angle similar to that of the anterior projection, approximately 120° relative to the dorsal surface of the ramus.

The jugal would articulate with the ventrally curving posterior end of the ramus if it were preserved. The lacrimal, also not preserved, would articulate along the relatively flat dorsal surface of the ramus between the lateral ridge and the medial flange.

The lateral surface of the ramus also extends ventrally to form the labial margin of the maxillary tooth row. Each alveolus is delineated partially by a vertical ridge projecting medially from the labial margin. The alveoli are also distinguished lingually by a series of pentagonal dental plates that run the length of the ramus. The dental plates are large and disconnected from each other anteriorly, whereas those more posterior are smaller and joined together. Both maxillae preserve teeth, with more on the left than on the right.

The left maxilla retains ten teeth while the right maxilla retains only seven. However, the teeth on the right maxilla are in generally better condition than those on the left and will be described more fully in the Dentition section.

4.2.3 Nasal

The left nasal is preserved as a small fragment from the posterior portion of the bone, near the articulation point with the prefrontal. The fragment is L-shaped in dorsal view, bearing short portions of the anterior and lateral processes extending from the main body of the nasal. In most straight-on views, the main body of the nasal appears robust.

However, this is an illusion caused by the lateral arching of the main body, which creates a concave depression on the nasal's medial surface. The main body of the nasal is actually relatively thin mediolaterally. The preserved portion of the anterior process is

Texas Tech University, Joshua Sundgren, May 2021 robust compared to the main body and exhibits a roughly triangular cross-section, rounded where the lateral facing vertex would be. The remainder of the lateral process is broader than the anterior process but shares the thinness of the main body. On the lateral surface, a deeply inset foramen is oriented parallel to the process itself and sheltered by an overhang of bone. The foramen is more plainly visible in ventral view, and the lateral process exhibits a teardrop-shaped cross-section, narrow posteriorly while thicker and rounded anteriorly. A mediolaterally oriented sulcus with uneven margins and a short, rounded projection at its medial end can be seen in the posterior view. The posteriorly oriented projection, likely part of the articulation with the prefrontal, is bisected by a ridge that continues partway into the sulcus.

4.2.4 Frontal

The two frontals are relatively flat bones that meet along the midline. This bone is intimately fused with the prefrontal anteriorly. In dorsal view, the frontal is rectangular at its anterior end. Posteriorly, the frontal flares into two short, broad processes that articulate with the postorbital laterally and the parietal farther posteriorly. A shallow fossa is present on the frontal's dorsal surface just anterior to the parietal process, on which a small fragment of the parietal is still fused, described by Zhang et al. (2020) as the parasagittal depression. In the ventral view, a prominent ridge lies on the frontal, originating at the articulation point with the prefrontal, which arches medially and curves back laterally to form the ventral margin of the postorbital process. The lateral curve of the postorbital process forms the posterodorsal margin of the orbital fenestra, while the curve between the postorbital process and the parietal process forms the dorsal margin of the supratemporal fenestra. Only the posterior process of the prefrontal is preserved.

Texas Tech University, Joshua Sundgren, May 2021

Anteriorly, the process curves ventrally, forming the anterodorsal margin of the orbital fenestra, before terminating abruptly.

4.2.5 Prefrontal

The prefrontal is a complex triangular element on the skull roof with a ventral process that extends along the posterior surface of the lacrimal bar. The prefrontal appears to be particularly robust from several perspectives, but in medial and anterior views, it can be seen that the medial face of the prefrontal is concave. The prefrontal looks hollow from these perspectives. In the anterior view, the thin outer surface of the prefrontal forms an

L-shape projecting medially and ventrally. Near the anterior end of the prefrontal is a dorsoventrally oriented ridge with a triangular cross-section. At the articulation point between the prefrontal and the frontal, a small triangular fragment of the prefrontal is missing, but the joint is otherwise intact.

4.2.6 Postorbital

The postorbital is a triradiate bone consisting of three processes that form approximately 120° angles with each other. All three processes are preserved to some extent, though only the posterodorsal process is close to fully intact. A comparison to a complete Massospondylus carinatus postorbital was useful in determining the proper orientation of this postorbital (Chapelle and Choiniere, 2018). The posterodorsal process is expanded mediolaterally relative to the other two processes and appears as if its apex may have been rounded off in order to articulate with the squamosal. This area, however, has sustained some chipping over time. The anterodorsal process would have articulated with the frontal. Unfortunately, this process has been broken off near its base, so a description of the articulation point is not possible. The anterodorsal process

Texas Tech University, Joshua Sundgren, May 2021 considerably narrows mediolaterally compared to the posterodorsal process and bears a distinctive triangular cross-section. The ventral process is much thinner mediolaterally than the other two and is also broken off near to its base. Based on comparison to the complete postorbital mentioned previously, the ventral process would likely have curved anteriorly and articulated with the jugal.

4.2.7 Quadrate

The left quadrate is preserved in good condition. The shaft of the quadrate is robust and exhibits a gentle S-shaped curve posteriorly to accommodate the eardrum. This end is mediolaterally expanded relative to the shaft and forms asymmetrical condyles on either side with a shallow depression between them. The lateral condyle is broader, but the medial condyle is expanded more ventrally. This condylar surface creates the jaw joint for articulating with the articular of the lower jaw. As described by Zhang et al.

(2020), the shaft is divided into an anterolateral wing and an anteromedial wing.

Together, these two wings form a V-shaped channel on the anterolateral surface of the quadrate on which the dorsal process of the quadratojugal and the ventral process of the squamosal would have articulated. Both wings are asymmetrical and rounded, but the anteromedial wing is substantially larger than the anterolateral wing. The outer ventral corner of the anteromedial plate is broken off, but the wing is otherwise intact. The smaller anterolateral wing appears to be fully intact, although the quadrate foramen mentioned by Zhang et al. (2020) is not visible on this specimen. In posterior view, the quadrate shaft is at its mediolateral narrowest behind the wings, and the area on either side of the shaft where the wings attach is excavated and made concave.

Texas Tech University, Joshua Sundgren, May 2021

Figure 4.2 Bones of the Skull Roof - Preserved bones of the skull roof, photos taken by Bill Mueller. A, premaxilla in lateral view; B, maxilla in lateral view; C, postorbital in lateral view; D, nasal in dorsal view; E, prefrontal-frontal complex in dorsal view; F, quadrate in lateral view. Scale bar = 1 cm relative to corresponding bone.

Texas Tech University, Joshua Sundgren, May 2021

Figure 4.3 Line drawings of skull roof bones - A, premaxilla in lateral view; B, maxilla in lateral view; C, postorbital in lateral view; D, nasal in dorsal view; E, prefrontal-frontal complex in dorsal view; F, quadrate in lateral view.

Texas Tech University, Joshua Sundgren, May 2021

4.3 PALATAL COMPLEX

4.3.1 Vomer

The left vomer is a small, curiously shaped bone (Figures 4.4, 4.5). The vomer appears to be missing small parts of its posterior end but is roughly triangular in dorsal view, narrow at the anterior end and gently widening posteriorly. The posterior third of the vomer projects medially slightly, then abruptly twists ventrally as a thin plate of bone.

This gives a corkscrew appearance to the vomer. The bony plate is curved along its outer margin and narrows toward the anterior end. Both the lateral and medial surfaces of the vomer are concave.

4.3.2 Pterygoid

The pterygoid is one of the most complex bones in the Jingshanosaurus skull. In lateral view, the main body of the pterygoid is roughly square and extends into four distinct parts. The pterygoid is mediolaterally thin and bears a shallow fossa between the posterodorsal and medial processes. The anterior palatine process tapers slightly anteriorly and bears a rounded bony projection on its ventral edge, which articulates with the ectopterygoid. Directly opposite of the palatine process is a short, posteriorly projecting, medial process. In the posterior view, a thin, triangular spur of bone projects medially and, together with the medial process, creates an articulation point with the basipterygoid. The quadrate ramus projects posteroventrally at an angle between 30° and

45° relative to the medial flange and terminates in a triangular bone fragment. Directly opposite of the quadrate ramus is an additional process that extends posterodorsally at an angle between 30° and 45° relative to the medial flange. This process is approximately half as long as the quadrate ramus and is broken off at its distal end.

Texas Tech University, Joshua Sundgren, May 2021

4.3.3 Ectopterygoid

The left ectopterygoid is only preserved as an L-shaped fragment consisting of a partially intact anterior ramus, a rectangular portion of the dorsal process, and an even smaller portion of the ventral projection. The anterior ramus is dorsoventrally thin and curves slightly ventrally toward its anterior end. The ramus is broken along its lateral and anterior margins, so the full extent of the ramus is not known. The dorsal process makes a near-90° angle with the ramus. The process appears to have been sheared off at an angle, so the shape of the remainder of the process cannot be determined. The preserved portion of the ventral projection is spade-shaped and forms a rounded notch with the ventral surface of the anterior ramus.

Texas Tech University, Joshua Sundgren, May 2021

Figure 4.4 Palate Bones - Preserved bones of the palatal complex, photos taken by Bill Mueller. A, pterygoid in lateral view; B, ectopterygoid in lateral view; C, vomer in dorsal view. Scale bar = 1 cm.

Texas Tech University, Joshua Sundgren, May 2021

Figure 4.5 Line drawings of palatal complex bones - A, pterygoid in lateral view; B, ectopterygoid in lateral view; C, vomer in dorsal view.

Texas Tech University, Joshua Sundgren, May 2021

4.4 LOWER JAW 4.4.1 Dentary

The left dentary is straight and rectangular in shape, comprising more than fifty percent of the total mandibular length (Figures 4.6, 4.7). The height of the dentary is relatively constant down its length. The lateral surface of the dentary bears a low, longitudinal ridge that arches very slightly ventrally and runs roughly two-thirds of the length of the dentary. Above this ridge is a set of approximately nine nutrient foramina, just ventral to the alveolar margin. A short row of smaller foramina is present at the dentary's anterior end, ventral to the more prominent foramina. A single large foramen is present on the medial side of the dentary, near its anterior end. Posteriorly, the lateral surface extends ventrally past the dentary's main body, forming a thin plate of bone, slightly chipped along its edge, shielding the posterior end of the dentary. The ventral border of the dentary is not perfectly smooth but rather bumpy. A series of low hemispherical projections that correspond to nearly every alveoli runs along the length of the dentary. There is a point near where the lateral surface begins to extend past the ventral margin of the dentary when the projections disappear briefly, but they reappear near the posterior end. The tooth row takes up most of the dorsal margin of the dentary and retains eighteen teeth out of a maximum of nineteen. This number of teeth is slightly lower than the estimate of Zhang et al. (2020), who proposed twenty-two teeth could have existed in the left dentary of LFGT-ZLJ0113. The six posterior-most and six anterior-most teeth are tightly packed together, while the middle six teeth are more spaced out. The medial margin of the alveoli is formed by small plates, as in the maxillae, though the plates here are more fan-shaped. They are narrow at the base and widen dorsally but lack the maxillary plates' defined point. All of the plates visible are

Texas Tech University, Joshua Sundgren, May 2021 disconnected from each other, and those more posterior are smaller than those at the anterior end. In the middle of the medial side, the row of plates is interrupted by a thin sheet of bone that appears almost like it has been grafted to the surface of the bone.

Comparison to other Jingshanosaurus dentaries would be useful here in order to determine if this sheet is normal or if this may represent pathology of some sort.

4.4.2 Surangular

Only a fragment of the left surangular is preserved, and it is broken on both ends.

The fragment gently bows cranially and tapers posteriorly in lateral view. In the anterior view, the surangular is very thin transversely, except near the cranial margin, which thickens medially. The structure of the fragment indicates it originates from close to the anterior end of the surangular, near the articulation with the dentary and broken just prior to the posterodorsal margin of the external mandibular fenestra. The cranially bowed ventral margin represents the articulation surface between the surangular and the angular.

In the medial view, the inflection of the dorsal margin is preserved, forming the coronoid eminence. Similar to that described by Zhang et al. (2020), a small foramen lies just posterior to the coronoid eminence, and the medial surface of the surangular is concave.

4.4.3 Articular

The left articular is a small, straight bone that is flat on its lateral surface to articulate with the surangular. Anteriorly, a short, thin flange of bone projects forward in front of the glenoid. The glenoid itself is rounded and lies just anterior to the glenoid fossa.

Posterior to the glenoid is a short, stout process that projects medially and is fused on its lateral side to the glenoid. The retroarticular process has a blunt posterior tip, and midway along its length on the medial edge, a spur of bone projects dorsally. The apex

Texas Tech University, Joshua Sundgren, May 2021 of the spur appears to be broken off. Ventral to the spur is a concave area where the medial process joins with the retroarticular process. A small, shallow foramen can be seen on the ventral surface of the medial process.

Texas Tech University, Joshua Sundgren, May 2021

Figure 4.6 Lower Jaw Bones - Preserved bones of the lower jaw, photos taken by Bill Mueller. A, articular in dorsal view; B, surangular in lateral view; C, dentary in lateral view. Scale bar = 1 cm relative to corresponding bone.

Texas Tech University, Joshua Sundgren, May 2021

Figure 4.7 Line drawings of lower jaw bones - A, articular in dorsal view; B, surangular in lateral view; C, dentary in lateral view.

Texas Tech University, Joshua Sundgren, May 2021

4.5 DENTITION

The dentition of Jingshanosaurus consists of long, weakly heterodont, laterally compressed spatulate teeth, with coarse vertical serrations on the crown, though these serrations do not continue down the shaft of the teeth. There are four premaxillary teeth, sixteen maxillary teeth, and either nineteen or twenty dentary teeth. The crown morphology of all teeth, both anterior and posterior, is spoon-shaped as in some sauropods (Figures 4.8, 4.9). The crowns of the upper and lower jaws are overlapping and slide past each other. Together they form a cutting edge, similar to a garden shear, to slice twigs and leaves. The jaw motion was essentially orthal. Wear facets are not prominent but are weakly visible on some maxillary and dentary teeth. The pattern of wear facts suggests that the upper tooth row of the premaxilla and maxilla slides past the labial side of the lower tooth series on the dentary.

Teeth are retained on the left and right premaxillae, maxillae, and left dentary. Many of the preserved teeth are broken apically, though a small number are nearly or totally complete. The left premaxilla has four alveoli with three preserved teeth, but the right premaxilla is somewhat damaged and retained three alveoli, each bearing a broken tooth.

The damage sustained by the right premaxilla exposes more of the roots of the premaxillary teeth, revealing they are set deep in the main body of the premaxilla.

Compared to those of the maxilla and the dentary, the premaxillary teeth have the longest crowns and most robust shafts in the mouth of Jingshanosaurus, though all teeth share a similar shape. As described by Zhang et al. (2020), they are long, lanceolate, and labiolingually compressed apically. Near their base, the teeth have a circular cross-

Texas Tech University, Joshua Sundgren, May 2021 section. Closer to the crown of each tooth, the labial surfaces retain a convex shape while the lingual surfaces flatten out, giving the teeth a semicircular cross-section.

The premaxillary teeth appear as though they would gently curve posteriorly, but it is difficult to know because they are broken near the roots. The tooth enamel on the labial surfaces is smooth and striated longitudinally. The lingual surfaces are also smooth and striated, but not to the same extent as the labial surfaces. The premaxillary teeth and some maxillary teeth are packed tightly together, as are the anterior-most and posterior- most teeth of the dentary, though the central dentary teeth are more spaced out. The apices of dentary teeth are oriented anteriorly, particularly those at the posterior end. The closely packed teeth exhibit a consistent arrangement in which the posterior margin of one tooth overlaps the anterior margin of the tooth immediately preceding it, creating tightly bound tooth batteries. Many teeth in the dentary are of different heights, a condition that is not simply the result of damage to the teeth, indicating constant tooth regrowth similar to that observed in other sauropodomorphs. The compression of the teeth in the maxillae varies between the two bones. Teeth in the right maxilla are more closely packed together in an arrangement similar to those in the dentary, whereas equivalent teeth in the left maxilla have space between them.

Teeth in both maxillae share a similar orientation in which the anterior margins of the teeth are facing slightly medially. This appears to be the case in the premaxillae, but not in the dentary, where the anterior margins are oriented straight ahead. The tooth serrations mentioned by Zhang et al. (date) are very poorly preserved and only visible on a couple of teeth from the right maxilla. The foremost teeth in both the premaxillae and dentary are inset a short distance from the anterior tips of their respective bones. In all,

Texas Tech University, Joshua Sundgren, May 2021 there is space for a maximum of twenty teeth per side in the upper jaw and nineteen, possibly twenty teeth per side in the lower jaw.

The teeth are set in sockets and are bordered lingually by the interdental plates.

Replacement activity is clear in the jaw showing varying developmental stages along with some empty alveoli and replacement window at the lingual side.

The style of teeth observed in Jingshanosaurus are similar to those seen in true sauropods, but are rarely seen in the basal sauropodomorphs. A number of sauropodomorphs have more leaf shaped teeth, flat and broad near the base while tapering toward the crown. Many also have denticles down each side of the tooth, whereas the denticles of Jingshanosaurus are restricted to the crown. Among the sauropodomorphs with teeth most similar to Jingshanosaurus are Irisosaurus and

Lamplughsaura, which is either a basal sauropodomorph or a basal sauropod described by Kutty et al. (2007). The teeth of Irisosaurus are more curved medially than those of

Jingshanosaurus but the mesiodistally widest point of the crown is at mid-height and the tooth enamel is finely wrinkled, both of which are characteristics observed in

Jingshanosaurus. Lamplughsaura shares the widest point of the crown characteristic with Jingshanosaurus as well. Few other sauropodomorphs share many dentition traits with Jingshanosaurus. The teeth of Jingshanosaurus are more like the peg-like teeth of sauropods like Diplodocus, Barosaurus, and Apatosaurus. The occurrence of long, spatulate, sauropod-like teeth in Jingshanosaurus may represent the first time this style of dentition evolved and was carried over into the clade Sauropoda.

Texas Tech University, Joshua Sundgren, May 2021

Figure 4.8 Jingshanosaurus dentition - Close up photographs of Jingshanosaurus dentition. A, B, premaxilla dentition in lateral and medial views respectively; C, D, maxilla dentition in lateral and medial views respectively; E, F, dentary dentition in lateral and medial views respectively. Scale bar = 1 cm relative to corresponding teeth.

Texas Tech University, Joshua Sundgren, May 2021

Figure 1.9 Line drawings of Jingshanosaurus dentition - A, B, premaxilla dentition in lateral and medial views respectively; C, D, maxilla dentition in lateral and medial views respectively; E, F, dentary dentition in lateral and medial views respectively.

Texas Tech University, Joshua Sundgren, May 2021

CHAPTER 5

PHYLOGENETIC ANALYSIS

This study utilizes the phylogenetic dataset and parameters employed by Zhang et al. (2020), adding IVPP-13246 as a taxa to the previously described Jingshanosaurus skulls LFGT-ZLJ0113, which is the holotype, and CXM-LT9401. The overall data matrix features 120 cranial characters out of 364 total characters and 62 taxa counting

IVPP-13246. A list of the cranial characters is provided in Appendix I. Phylogenetic analyses were performed using PAUP*4.0a169, applying a heuristic search of 1000 replicates and tree bisection-reconnection (TBR) with 10 trees saved per replication. All characters were equally weighted and 43 multistate characters were coded as ordered.

Out of the 120 cranial characters, a total of 68 characters could be scored for IVPP-13246 based off of the preserved material. This is lower than the number scored for LFGT-

ZLJ0113 and CXM-LT9401, which had 91 and 103 characters scored, respectively. The main reason for fewer scored characters in IVPP-13246 is the number of bones missing.

However, the high quality preservation and disarticulated nature of the specimen could lead to new characters being described in the future.

The phylogenetic analysis generated eighteen most parsimonious trees (MPTs) with the following scores: tree length = 1,298 steps, consistency index (CI) = 0.332, and retention index (RI) = 0.690. The strict consensus tree (Figure 5.1) is well-resolved and is nearly identical to the tree reconstructed by Zhang et al. (2020). The only difference between the two is the inclusion of IVPP-13246, which as expected, is added to the polytomy consisting of LFGT-ZLJ0113 and CXM-LT9401, altogether representing

Jingshanosaurus on the phylogeny. Zhang et al. (2020) list four main synapomorphies

Texas Tech University, Joshua Sundgren, May 2021 that distinguish Jingshanosaurus from other basal sauropodomorphs: the level of the posterior margin of the external naris being posterior to the mid-length of the maxillary tooth row and the anterior margin of the antorbital fenestra (character.state: 19.2); a height-to-length ratio of the dentary greater than 0.2 (character.state: 98.1); the length of the retroarticular process is greater than the depth of the mandible below the glenoid

(character.state: 105.1); and tooth crowns with a distally recurved long axis

(character.state: 116.0). Despite the lower overall number of characters scored compared to the other two skulls, IVPP-13246 still bears these four important characters with the same states as the others. A number of characters of IVPP-13246 were scored differently from the others, either because they appear in a different state or had not been scored previously: the width of the nasal anteroventral process being less at its base than the width of the nasal anterodorsal process at its base (character.state: 22.0); posteriorly tapering main body of the maxilla (character.state: 27.0); a deeply impressed antorbital fossa on the ascending ramus of the maxilla that is delimited by a sharp, scarp-like rim

(character.state: 31.0); an elongated caudal process of the prefrontal (character.state:

43.1); a vomer which is less than .25 of the total skull length (character.state: 93.0); and longitudinal labial grooves on the teeth (119.1). Characters 27, 31, and 119 are the three which have been scored differently from the other two skulls and the reasons for that are unclear. It may simply be because these particular bones have been preserved better here, particularly in the case of 119, which relates to the very well-preserved teeth. These bones may also represent a juvenile, which could also account for differences. The complete character scoring of IVPP-13246 is summarized in the following table.

Texas Tech University, Joshua Sundgren, May 2021

Table 1 – Phylogenetic Character Scoring of IVPP-13246

?0?1010210 ??2111112? ?01?110111 011000???? ??10??????

??011??0?0 ???????101 1?????????? ??????000? ?1010?1101

0??0110110 0101001011?

As discussed by Zhang et al. (2020), Jingshanosaurus was recovered as the second diverging clade of Sauropodiformes between Xingxiulong and Yunnanosaurus and represent the most basal members of the clade. That study provides a thorough description of the key cranial differences between these three taxa.

Figure 5.1 Sauropodomorph Phylogeny - Reconstructed phylogeny showing the position of IVPP-13246 relative to other basal sauropodomorphs, near the divergence of the Sauropodiformes clade; Jingshanosaurus skulls marked in blue.

Texas Tech University, Joshua Sundgren, May 2021

One noteworthy result from this analysis, as well as previous analyses, is an unusual paleogeographical distribution of closely aligned genera. For example, the polytomy just above Xingxiulong contains Coloradisaurus, Glacialisaurus, and

Lufengosaurus, which are found in South America, Antarctica, and the Lufeng Basin, respectively. It should be noted that Coloradisaurus lived earlier than the other two in the Late Triassic while Glacialisaurus and Lufengosaurus lived within a few million years of each other in the Early Jurassic. South America and Antarctica were near to each other on the continent of Gondwana in the Late Triassic and Early Jurassic but

South China was a significant distance away in Laurasia. This could represent an instance of convergent evolution among the basal sauropodomorphs or an extremely rapid migration and speciation of basal sauropodomorphs from Gondwana to Laurasia.

The path that animals would have had to take requires passing through present-day North

America, which has very few endemic basal sauropodomorphs. It could also simply represent a need for more material and subsequent analyses. The inconsistency and biogeographical uncertainty present in basal sauropodomorph phylogenies has been noted in previous studies, such as Bittencourt et al. (2012), who noted that Brazilian

“prosauropods” appear to be more closely related to plateosaurids from Europe than

Argentinian sauropodomorphs. They also noted that the range between Brazil and

Europe also includes North America and northern Africa, neither of which have many endemic basal sauropodomorphs. There is great potential here for future studies which combine both phylogenetic analyses of the basal sauropodomorphs with biogeogprahic studies to better understand how they spread throughout the world.

Texas Tech University, Joshua Sundgren, May 2021

CHAPTER 6

SUMMARY

Jingshanosaurus xinwaensis is an important member of the rich faunal assemblage from the Lufeng Basin of southern China as well as the broader clade of basal sauropodomorphs. As shown in the phylogenetic analysis, Jingshanosaurus occupies a notable position on the reconstructed phylogeny near the divergence of the clade Sauropodiformes from the rest of the basal sauropodomorphs. This represents the early stages of the gradual emergence of the true sauropods during the Jurassic Period.

Because of its phylogenetic position relative to other sauropodomorphs and the diversity of the region in which it lived, particularly in regards to contemporary sauropodomorphs, it is important to know as much as possible about Jingshanosaurus and its anatomy.

Jingshanosaurus has suffered from a lack of well described cranial material, which can cause issues when determining the phylogenetic position of animals, particularly among groups with similar post-cranial body plans such as sauropodomorphs. This project has sought to address this problem by describing and analyzing new Jingshanosaurus cranial material, IVPP-13246. These skull bones are disarticulated, undistorted, and preserved in good quality. A total of 14 bones are present: the left and right premaxillae and maxillae, and the left nasal, postorbital, prefrontal-frontal complex, quadrate, vomer, pterygoid, ectopterygoid, dentary, surangular, and articular. The bones provide valuable insights into the animal’s anatomy and lifestyle, particularly in regard to the dentition and feeding, as many of the teeth are preserved in good condition. Important details that can be determined from the teeth are that denticles are only present on the carinae of the teeth and that the medial side of upper dentition occludes with the labial side of the lower

Texas Tech University, Joshua Sundgren, May 2021 dentition, creating a scissor-like cutting surface. In comparison to other basal sauropodomorphs, the teeth of Jingshanosaurus are very different and are more similar to those observed in many sauropods. This may represent the first occurrence of this style of teeth among the sauropodomorphs. The phylogenetic analysis was hindered somewhat by the absence of a number of key cranial bones, such as the lachrimal, the jugal, and the quadratojugal. However, the material in this study includes bones not accounted for in other skulls, such as the vomer and the partial nasal. This allows for some characters to be scored which previously could not be. Despite fewer characters scored overall and several scored differently, IVPP-13246 was still recovered in a polytomy with two other skulls, LFGT-ZLJ0113 and CXM-LT9401, altogether representing Jingshanosaurus on the phylogeny. Jingshanosaurus did not change position in the reconstructed phylogeny which provides robust support for the previous findings of Zhang et al. (2019), particularly in light of the drastically different character scores. Furthermore, there is great potential for future studies of IVPP-13246. The material studied here, particularly the bones not present or well-preserved in other skulls, may provide brand new characters which could be scored for all sauropodomorphs on the phylogeny. This could lead to further clarification of the relationships between the basal sauropodomorphs, which is significant given their close association with both the earliest dinosaurs and the true sauropods. The status of basal sauropodomorphs as transitional between these two groups makes understanding their relationships crucial to a broader understanding of a large portion of dinosaurs overall.

Texas Tech University, Joshua Sundgren, May 2021

BIBLIOGRAPHY

Apaldetti, Cecilia, Ricardo N. Martinez, Oscar A. Alcober, and Diego Pol. "A new basal sauropodomorph (Dinosauria: Saurischia) from Quebrada del Barro Formation (Marayes- El Carrizal Basin), northwestern Argentina." PLoS One 6, no. 11 (2011): e26964. Barrett, Paul M., Paul Upchurch, and Wang Xiao-Lin. "Cranial osteology of Lufengosaurus huenei Young (Dinosauria: Prosauropoda) from the Lower Jurassic of Yunnan, People's Republic of China." Journal of Vertebrate Paleontology 25, no. 4 (2005): 806-822. Barrett, Paul M., Paul Upchurch, Xiao-Dong Zhou, and X-L. Wang. "The skull of Yunnanosaurus huangi Young, 1942 (Dinosauria: Prosauropoda) from the Lower Lufeng Formation (Lower Jurassic) of Yunnan, China." Zoological Journal of the Linnean Society 150, no. 2 (2007): 319-341. Benton, Michael J., Lars Juul, Glenn W. Storrs, and Peter M. Galton. "Anatomy and systematics of the prosauropod dinosaur Thecodontosaurus antiquus from the Upper Triassic of southwest England." Journal of Vertebrate Paleontology 20, no. 1 (2000): 77- 108. Bien, Meinian. "“Red Beds” of Yunnan." Bulletin of the Geological Society of China 21, no. 2‐4 (1941): 157-198. Bittencourt, Jonathas S., Luciano A. Leal, Max C. Langer, and Sergio AK Azevedo. "An additional basal sauropodomorph specimen from the Upper Triassic Caturrita Formation, southern Brazil, with comments on the biogeography of plateosaurids." Alcheringa: An Australasian Journal of Palaeontology 36, no. 2 (2012): 269-278. Bonaparte, Jose F. (1969). “Dos nuevas "faunas" de reptiles triásicos de Argentina.” Ameghiniana 10(1) (1969): 89-102. Bonaparte, Jose F., Jorge Ferigolo, and Ana Maria Ribeiro. "A new early Late Triassic saurischian dinosaur from Rio Grande do Sul state, Brazil." National Science Museum Monographs 15 (1999): 89-109. Bonaparte, Jose F., G. Brea, C. L. Schultz, and A. G. Martinelli. "A new specimen of Guaibasaurus candelariensis (basal Saurischia) from the Late Triassic Caturrita Formation of southern Brazil." Historical Biology 19, no. 1 (2007): 73-82. Broom, Robert. “On the dinosaurs of the Stormberg, South Africa.” Annals of the South African Museum 7 (1911): 291–308. Cabreira, Sergio F., Cesar L. Schultz, Jonathas S. Bittencourt, Marina B. Soares, Daniel C. Fortier, Lúcio R. Silva, and Max C. Langer. "New stem-sauropodomorph (Dinosauria, Saurischia) from the Triassic of Brazil." Naturwissenschaften 98, no. 12 (2011): 1035- 1040.

Texas Tech University, Joshua Sundgren, May 2021

Chapelle, Kimberley EJ, and Jonah N. Choiniere. "A revised cranial description of Massospondylus carinatus Owen (Dinosauria: Sauropodomorpha) based on computed tomographic scans and a review of cranial characters for basal Sauropodomorpha." PeerJ 6 (2018): e4224. Chatterjee Sankar. Quest for the dinosaurs in the land of dragons. M (Museum of Texas Tech University), Fall-Winter, (2019) p. 35-41. Cooper, Michael R. "The prosauropod dinosaur Massospondylus carinatus (Owen) from Zimbabwe: Its biology, mode of life and phylogenetic significance." Occas. Pap. Natl. Monuments Rhod. 6, no. 10 (1981): 690-840. Dodson, Peter, and Susan D. Dawson. "Making the fossil record of dinosaurs." Modern Geology 16 (1991): 3-15. Dong, Zhiming. “Dinosaurian faunas of China.” Beijing: China Ocean Press (1992): p. 188. Ezcurra, Martin D. "A new early dinosaur (Saurischia: Sauropodomorpha) from the Late Triassic of Argentina: a reassessment of dinosaur origin and phylogeny." Journal of Systematic Palaeontology 8, no. 3 (2010): 371-425. de Fabrègues, Claire Peyre, Shundong Bi, Hongqing Li, Gang Li, Lei Yang, and Xing Xu. "A new species of early-diverging Sauropodiformes from the Lower Jurassic Fengjiahe Formation of Yunnan Province, China." Scientific Reports 10, no. 1 (2020): 1- 17. Fang, X. S., Q. J. Pang, L. W. Lu, Z. X. Zhang, S. G. Pan, Y. M. Wang, X. K. Li, and Z. W. Cheng. "Lower, middle, and upper Jurassic subdivision in the Lufeng region, Yunnan Province." In Proceedings of the Third National Stratigraphical Congress of China, pp. 208-214. Beijing: Geological Publishing House, 2000. Fu, Qiang, Jose Bienvenido Diez, Mike Pole, Manuel García Ávila, Zhong-Jian Liu, Hang Chu, Yemao Hou et al. "An unexpected noncarpellate epigynous flower from the Jurassic of China." Elife 7 (2018): e38827. Galton, Peter M. "Prosauropod dinosaurs (Reptilia: Saurischia) of North America." Postilla (1976): 1-98. Galton, Peter M. "Sex, sacra and Sellosaurus gracilis (Saurischia, Sauropodomorpha, Upper Triassic, Germany)-or why the character." Neues Jahrbuch für Geologie und Paläontologie-Abhandlungen (1999): 19-55. Galton, Peter M., and Paul Upchurch. "Prosauropod dinosaurs: homeotic transformation (" frame shifts") with third sacral as a caudosacral or a dorsosacral." In Journal of Vertebrate Paleontology, vol. 20, no. 3 (2000): p. 43A.

Texas Tech University, Joshua Sundgren, May 2021

Galton, Peter M. "Prosauropod dinosaurs from the Upper Triassic of Germany", In Colectivo Arqueologico-Paleontologico de Salas, C.A.S. (Eds.): Actas de las I Jornadas Internacionales sobre Paleontologia de Dinosaurios y su Entorno [Proceedings of the First International Symposium on Paleontology of Dinosaurs and Their Environment], (2001): 25–92. Galton, Peter M., and Paul Upchurch. "12. Prosauropoda." In The Dinosauria, second edition, University of California Press, (2004): pp. 232-258. Galton, Peter M., Adam M. Yates, and Diane Kermack. "Pantydraco n. gen. for Thecodontosaurus caducus Yates, 2003, a basal sauropodomorph dinosaur from the Upper Triassic or Lower Jurassic of South Wales, UK." Neues Jahrbuch für Geologie und Paläontologie-Abhandlungen (2007): 119-125. Gauthier, Jacques A. . “Saurischian monophyly and the origin of birds”. In The Origin of Birds and the Evolution of Flight. California Academy of Sciences, Memoir 8 Edited by: Padian, K. (1986): 1–55. Huene, F. v. “Die Dinosaurier der Europäischen Triasformation mit berücksichtigung der Ausseuropäischen vorkommnisse.” Geologische und Palaeontologische Abhandlungen Suppl. 1(1) (1908): 1-419 Huene, F. v. “Die fossile Reptile-Ordnung Saurischia, ihre Entwicklung und Geschichte.” Indukt. Abstamm. Ver. 24 (1932): 162-166 Huxley, T.H. “On the remains of large dinosaurian reptiles from the Stormberg Mountains, South Africa.” Geological Magazine 3 (1866): 563. Kitching, James W., and Michael A. Raath. "Fossils from the Elliot and Clarens Formations (Karoo Sequence) of the northeastern Cape, Orange Free State and Lesotho, and a suggested biozonation based on tetrapods." Palaeontologia Africana, 25: (1984). Kobayashi, Teiichi. "The early stage of the Burmese-Malayan Geosyncline." (1973). Kutty, T. S., Sankar Chatterjee, Peter M. Galton, and Paul Upchurch. "Basal sauropodomorphs (Dinosauria: Saurischia) from the Lower Jurassic of India: their anatomy and relationships." Journal of Paleontology 81, no. 6 (2007): 1218-1240. Langer, Max C., Fernando Abdala, Martha Richter, and Michael J. Benton. "A sauropodomorph dinosaur from the Upper Triassic (Carman) of southern Brazil." Comptes Rendus de l'Académie des Sciences-Series IIA-Earth and Planetary Science 329, no. 7 (1999): 511-517. Langer, Max C., Jahandar Ramezani, and Átila AS Da Rosa. "U-Pb age constraints on dinosaur rise from south Brazil." Gondwana Research 57 (2018): 133-140. Leal, L. A., A. Kellner, S. A. K. Azevedo and A. da Rosa. "A new early dinosaur (sauropodomorpha) from the Caturrita formation (late Triassic), Paraná Basin, Brazil." Zootaxa 690, no. 10 (2004): 1.

Texas Tech University, Joshua Sundgren, May 2021

Lee, Yao-Chang, Cheng-Cheng Chiang, Pei-Yu Huang, Chao-Yu Chung, Timothy D. Huang, Chun-Chieh Wang, Ching-Iue Chen, Rong-Seng Chang, Cheng-Hao Liao, and Robert R. Reisz. "Evidence of preserved collagen in an Early Jurassic sauropodomorph dinosaur revealed by synchrotron FTIR microspectroscopy." Nature communications 8, no. 1 (2017): 1-8. Lü, Junchang, Li Tianguang, Zhong Shimin, Azuma Yoichi, Fujita Masato, Dong Zhiming, and Ji Qiang. "New yunnanosaurid dinosaur (Dinosauria, Prosauropoda) from the Middle Jurassic Zhanghe Formation of Yuanmou, Yunnan Province of China." Memoir of the Fukui Prefectural Dinosaur Museum 6 (2007): 1-15. Lü, Junchang, Yoshitsugu Kobayashi, L. I. Tianguang, and Zhong Shimin. "A new basal sauropod dinosaur from the Lufeng Basin, Yunnan Province, Southwestern China." Acta Geologica Sinica‐English Edition 84, no. 6 (2010): 1336-1342. McPhee, Blair W., Adam M. Yates, Jonah N. Choiniere, and Fernando Abdala. "The complete anatomy and phylogenetic relationships of Antetonitrus ingenipes (Sauropodiformes, Dinosauria): implications for the origins of Sauropoda." Zoological Journal of the Linnean Society 171, no. 1 (2014): 151-205. McPhee, Blair W., Emese M. Bordy, Lara Sciscio, and Jonah N. Choiniere. "The sauropodomorph biostratigraphy of the Elliot Formation of southern Africa: Tracking the evolution of Sauropodomorpha across the Triassic–Jurassic boundary." Acta Palaeontologica Polonica 62, no. 3 (2017): 441-465. Mao, Lei, Lida Xing, Jianping Zhang, Tao Wang, and Donghao Wang. "Revisiting the world famous Lufeng Formation dinosaur fauna: new approaches to old problems." Historical Biology 32, no. 8 (2020): 1062-1070. Martinez, Ricardo N., and Oscar A. Alcober. "A basal sauropodomorph (Dinosauria: Saurischia) from the Ischigualasto Formation (Triassic, Carnian) and the early evolution of Sauropodomorpha." PLoS One 4, no. 2 (2009): e4397. Morris, John. A Catalogue of British Fossils. British Museum, London, (1843): 222 pp Müller, Rodrigo Temp, Max Cardoso Langer, and Sérgio Dias-da-Silva. "An exceptionally preserved association of complete dinosaur skeletons reveals the oldest long-necked sauropodomorphs." Biology letters 14, no. 11 (2018): 20180633. Müller, Rodrigo T., and Maurício S. Garcia. "Rise of an empire: analyzing the high diversity of the earliest sauropodomorph dinosaurs through distinct hypotheses." Historical Biology 32, no. 10 (2020): 1334-1339. Novas, Fernando E. "Dinosaur monophyly." Journal of vertebrate Paleontology 16, no. 4 (1996): 723-741.

Texas Tech University, Joshua Sundgren, May 2021

Novas, Fernando E., Martin D. Ezcurra, Sankar Chatterjee, and T. S. Kutty. "New dinosaur species from the Upper Triassic Upper Maleri and Lower Dharmaram formations of central India." Earth and Environmental Science Transactions of the Royal Society of Edinburgh 101, no. 3-4 (2010): 333-349. Owen, Richard. “Report on British fossil reptiles. Part II.” Reports of the British Association for the Advancement of Science, 11 (1842): 60–204. Owen, Richard. "Descriptive catalogue of the Fossil organic remains of Reptilia and Pisces contained in the Museum of the Royal College of Surgeons of England." London (1854): pp. 80, 97 Pol, Diego, and Jaime E. Powell. "Skull anatomy of Mussaurus patagonicus (Dinosauria: Sauropodomorpha) from the late Triassic of Patagonia." Historical Biology 19, no. 1 (2007): 125-144. Pretto, Flávio A., Max C. Langer, and Cesar L. Schultz. "A new dinosaur (Saurischia: Sauropodomorpha) from the Late Triassic of Brazil provides insights on the evolution of sauropodomorph body plan." Zoological Journal of the Linnean Society 185, no. 2 (2019): 388-416. Reisz, Robert R., Diane Scott, Hans-Dieter Sues, David C. Evans, and Michael A. Raath. "Embryos of an Early Jurassic prosauropod dinosaur and their evolutionary significance." Science 309, no. 5735 (2005): 761-764. Reisz, Robert R., Aaron RH LeBlanc, Hillary C. Maddin, Thomas W. Dudgeon, Diane Scott, Timothy Huang, Jun Chen, Chuan-Mu Chen, and Shiming Zhong. "Early Jurassic dinosaur fetal dental development and its significance for the evolution of sauropod dentition." Nature communications 11, no. 1 (2020): 1-9. Rozhdestvensky, Anatoly K. "Growth changes in Asian dinosaurs and some problems of their taxonomy." Paleontologicheskii Zhurnal (1965): 95-100. Sander, P. Martin, and Marcus Clauss. "Sauropod gigantism." Science 322, no. 5899 (2008): 200-201. Scotese, Christopher R. “The PALEOMAP Project PaleoAtlas for ArcGIS, Volume 3, Triassic and Jurassic Paleogeographic and Plate Tectonic Reconstructions.” PALEOMAP Project, Arlington, Texas. (2011). Sekiya, Toru. "A new prosauropod dinosaur from Lower Jurassic in Lufeng of Yunnan". Global Geology. 29 (1) (2010): 6–15. Sekiya, Toru, Xingsheng Jin, Wenjie Zheng, Masateru Shibata, and Yoichi Azuma. "A new juvenile specimen of Yunnanosaurus robustus (Dinosauria: Sauropodomorpha) from Early to Middle Jurassic of Chuxiong Autonomous Prefecture, Yunnan Province, China." Historical Biology 26, no. 2 (2014): 252-277.

Texas Tech University, Joshua Sundgren, May 2021

Seeley, Harry G. "I. On the classification of the fossil animals commonly named Dinosauria." Proceedings of the Royal Society of London 43, no. 258-265 (1888): 165- 171. Sereno, Paul C. “Prosauropod monophyly and basal sauropodomorph phylogeny.” Journal of Vertebrate Paleontology, 9 (Supplement to No. 3), (1989): 38A. Sereno, Paul C., Catherine A. Forster, Raymond R. Rogers, and Alfredo M. Monetta. "Primitive dinosaur skeleton from Argentina and the early evolution of Dinosauria." Nature 361, no. 6407 (1993): 64-66. Sereno, Paul C. "The evolution of dinosaurs." Science 284, no. 5423 (1999): 2137-2147. Sereno, Paul C. “Basal Sauropodomorpha: historical and recent phylogenetic hypothesis, with comments on Ammosaurus major (Marsh, 1889).” Spec. Pap. Palaeontol. 77 (2007): 261–289. Simmons, David Jay. The non-therapsid reptiles of the Lufeng Basin, Yunnan, China. Fieldiana: Geology 15 (1) (1965): p. 3-89. Smith, Nathan D., and Diego Pol. "Anatomy of a basal sauropodomorph dinosaur from the Early Jurassic Hanson Formation of Antarctica." Acta Palaeontologica Polonica 52, no. 4 (2007). Sun, Ailin, Guihai Cui, Yuhe Li, and X. C. Wu. "A verified list of Lufeng saurischian fauna." Vertebrata PalAsiatica 23, no. 1 (1985): 1-12. Swofford, David L. PAUP*. Phylogenetic Analysis Using Parsimony (*and Other Methods). Version 4. Sinauer Associates, Sunderland, Massachusetts. (2003). Upchurch, Paul. "The phylogenetic relationships of sauropod dinosaurs." Zoological Journal of the Linnean Society 124, no. 1 (1998): 43-103. Upchurch, Paul, Paul M. Barrett, and Peter Dodson. “13. Sauropoda.” In The Dinosauria, second edition, University of California Press, (2004): 259-322. Upchurch, Paul, Paul M. Barrett, and Peter M. Galton. "A phylogenetic analysis of basal sauropodomorph relationships: implications for the origin of sauropod dinosaurs." Special Papers in Palaeontology 77 (2007): 57. Von Meyer, H. "Briefliche Mitteilung an Prof. Bronn über Plateosaurus engelhardti." Neues Jahrbuch für Mineralogie, Geognosie, Geologie und Petrefakten-Kunde 1837 (1837): 314-316. Wang, Guo-fu. “The Jinshanosaurus discovered at Tanghai.” Lufeng Yunnan Geol 23 (2004):77–82. in Chinese. Wang, Ya-Ming, Hai-Lu You and Tao Wang. A new basal sauropodiform dinosaur from the Lower Jurassic of Yunnan Province, China. Scientific Reports, 7(1) (2017): pp.1-11.

Texas Tech University, Joshua Sundgren, May 2021

Wang, Ya‐Ming, Tao Wang, Zhi‐Wen Yang, and Hai‐Lu You. "Cranium and vertebral column of Xingxiulong chengi (Dinosauria: Sauropodomorpha) from the Early Jurassic of China." The Anatomical Record 303, no. 4 (2020): 772-789. Wilson, Jeffrey A., and Paul C. Sereno. "Early evolution and higher-level phylogeny of sauropod dinosaurs." Journal of Vertebrate Paleontology 18, no. S2 (1998): 1-79. Yates, Adam M. "A definite prosauropod dinosaur from the lower Elliot Formation (Norian: Upper Triassic) of South Africa." Palaeontologia Africana, 39: (2003). Yates, Adam M., and James W. Kitching. "The earliest known sauropod dinosaur and the first steps towards sauropod locomotion." Proceedings of the Royal Society of London. Series B: Biological Sciences 270, no. 1525 (2003): 1753-1758. Yates, Adam M., P. John Hancox, and Bruce S. Rubidge. "First record of a sauropod dinosaur from the upper Elliot Formation (Early Jurassic) of South Africa." South African Journal of Science 100 (2004). Yates, Adam. "The skull of the Triassic sauropodomorph, Melanorosaurus readi, from South Africa and the definition of Sauropoda." In Journal of Vertebrate Paleontology, vol. 25, no. 3 (2005): pp. 132A-132A. Yates, Adam M. "The first complete skull of the Triassic dinosaur Melanorosaurus Haughton (Sauropodomorpha: Anchisauria)." Evolution and palaeobiology of early sauropodomorph dinosaurs 77 (2007): 9-55. Young, Chung-Chien. "Gyposaurus sinensis Young (sp. nov.) A new Prosauropoda from the Upper Triassic beds at Lufeng, Yunnan". Bulletin of the Geological Society of China. 21 (2–4) (1941): 205–252. Young, Chung-Chien. "A complete osteology of Lufengosaurus huenei Young (gen. et sp. nov.)” Palaeontologica Sinica. Series C 7 (1941): 1-53. Young, Chung-Chien. "Yunnanosaurus huangi Young (gen. et sp. nov.) A new Prosauropoda from the Red Beds at Lufeng, Yunnan." Bulletin of the Geological Society of China. XXII. China (1942). Young, Chung-Chien. “On Lufengosaurus magnus Young (sp. nov.) and additional finds of Lufengosaurus huenei Young.” Geol. Survey of China, (1947). Young, Chung‐Chien. "The Lufeng saurischian fauna in China." Palaeontologia Sinica, New Series C 13 (1951): 1-96. Young, Chung-Chien. "A new fossil reptile from the Lufeng Basin." (1982): 36-37. (in Chinese). Young, Chung-Chien. “New developments on the study of the saurischian faunas from Lufeng, Yunnan, and the problem of its age.” Collected Papers of C.C. Young, pp. 14-20 (1982) (in Chinese).

Texas Tech University, Joshua Sundgren, May 2021

Young, Chung-Chien. "A protosuchian from Lufeng, Yunnan." Collected Papers of CC Young (1982): 26-28. Young, Chung-Chien. "A new ornithischian from Lufeng, Yunnan." Posthumous Papers of CC Young (1982): 29-35. Young, Chung-Chien. 1982. Two early mammals from Lufeng, Yunnan. Collected Papers of C.C. Young (1982): 21-25. Yunnan Redbed Corps, 1967. Measured section at Shawan, Lufeng Co. Zhang, Qian-Nan, Hai-Lu You, Tao Wang, and Sankar Chatterjee. "A new sauropodiform dinosaur with a ‘sauropodan’ skull from the Lower Jurassic Lufeng Formation of Yunnan Province, China." Scientific Reports 8, no. 1 (2018): 1-12. Zhang, Qian‐Nan, Tao Wang, Zhi‐Wen Yang, and Hai‐Lu You. "Redescription of the Cranium of Jingshanosaurus xinwaensis (Dinosauria: Sauropodomorpha) from the Lower Jurassic Lufeng Formation of Yunnan Province, China." The Anatomical Record 303, no. 4 (2020): 759-771. Zhang, Yihong, and Zhaolong Yang. "A Complete Osteology of Prosauropoda in Lufeng Basin Yunnan China - Jingshanosaurus.” Kunming: Yunnan Science and Technology Publishing House (1994).

Texas Tech University, Joshua Sundgren, May 2021

APPENDICES

A. LIST OF PHYLOGENETIC CHARACTERS

1. Skull to femur ratio: greater than 0.6 (0); less than 0.6 (1).

2. Lateral plates appressed to the labial side of the premaxillary, maxillary and dentary teeth: absent (0); present (1).

3. Relative height of the rostrum at the posterior margin of the naris: more than 0.6 the height of the skull at the middle of the orbit (0); less than 0.6 the height of the skull at the middle of the orbit (1).

4. Foramen on the lateral surface of the premaxillary body: absent (0); present (1). 5. Distal end of the dorsal premaxillary process: tapered (0); transversely expanded (1). 6. Profile of premaxilla: convex (0); with an inflection at the base of the dorsal process (1).

7. Size and position of the posterolateral process of premaxilla: large and lateral to the anterior process of the maxilla (0); small and medial to the anterior process of the maxilla (1).

8. Relationship between posterolateral process of the premaxilla and the anteroventral process of the nasal: broad sutured contact (0); point contact (1); separated by maxilla (2). Ordered.

9. Posteromedial process of the premaxilla: absent (0); present (1)

10. Shape of the anteromedial process of the maxilla: narrow, elongated and projecting anterior to lateral premaxilla-maxilla suture (0); short, broad and level with lateral premaxilla-maxilla suture (1).

11. Development of external narial fossa: absent to weak (0); well-developed with sharp posterior and anteroventral rims (1).

12. Development of narial fossa on the anterior ramus of the maxilla: weak and orientated laterally to dorsolaterally (0); well-developed and forming a horizontal shelf (1).

Texas Tech University, Joshua Sundgren, May 2021

13. Size and position of subnarial foramen: absent (0); small (no larger than adjacent maxillary neurovascular foramina) and positioned outside of narial fossa (1); large and on the rim of, or inside, the narial fossa (2). Ordered.

14. Shape of subnarial foramen: rounded (0); slot-shaped (1). 15. Maxillary contribution to the margin of the narial fossa: absent (0); present (1).

16. Diameter of external naris: less than 0.5 of the orbital diameter (0); greater than 0.5 of the orbital diameter.

17. Shape of the external naris (in adults): rounded (0); subtriangular with an acute posteroventral corner (1).

18. Level of the anterior margin of the external naris: anterior to the midlength of the premaxillary body (0); posterior to the midlength of the premaxillary body (1).

19. Level of the posterior margin of external naris: anterior to, or level with the premaxilla- maxilla suture (0); posterior to the first maxillary alveolus (1); posterior to the midlength of the maxillary tooth row and the anterior margin of the antorbital fenestra (2). Ordered.

20. Dorsal profile of the snout: straight to gently convex (0); with a depression behind the naris (2).

21. Elongate median nasal depression: absent (0); present (1).

22. Width of anteroventral process of nasal at its base: less than the width of the anterodorsal process at its base (0); greater than the width of the anterodorsal process at its base (1).

23. Nasal relationship with dorsal margin of antorbital fossa: not contributing to the margin of the antorbital fossa (0); lateral margin overhangs the antorbital fossa and forms its dorsal margin (1); overhang extensive, obscuring the dorsal lachrymal-maxilla contact in lateral view (2). Ordered.

24. Pointed caudolateral process of the nasal overlapping the lachrymal: absent (0); present (1).

Texas Tech University, Joshua Sundgren, May 2021

25. Anterior profile of the maxilla: slopes continuously towards the rostral tip (0); with a strong inflection at the base of the ascending ramus, creating a rostral ramus with parallel dorsal and ventral margins (1).

26. Length of rostral ramus of the maxilla: less than its dorsoventral depth (0); greater than its dorsoventral depth (1).

27. Shape of the main body of the maxilla: tapering posteriorly (0); dorsal and ventral margins parallel for most of their length (1).

28. Shape of the ascending ramus of the maxilla in lateral view: tapering dorsally (0); with an anteroposterior expansion at the dorsal end (1).

29. Rostrocaudal length of the antorbital fossa: greater than that of the orbit (0); less than that of the orbit (1).

30. Posteroventral extent of medial wall of antorbital fossa: reaching the anterior tip of the jugal (0); terminating anterior to the anterior tip of the jugal (1).

31. Development of the antorbital fossa on the ascending ramus of the maxilla: deeply impressed and delimited by a sharp, scarp-like rim (0); weakly impressed and delimited by a rounded rim or a change in slope (1).

32. Shape of the antorbital fossa: crescentic with a strongly concave posterior margin that is roughly parallel to the anterior margin of the antorbital fossa (0); subtriangular with a straight to gently concave posterior margin (1); antorbital fossa absent (2).

33. Size of the neurovascular foramen at the posterior end of the lateral maxillary row: not larger than the others (0); distinctly larger than the others in the row (1).

34. Direction that the neurovascular foramen at the posterior end of the lateral maxillary row opens: posteriorly (0); anteriorly, ventrally, or laterally (1).

35. Arrangement of lateral maxillary neurovascular foramina: linear (0); irregular (1).

36. Longitudinal ridge on the posterior lateral surface of the maxilla: absent (0); present (1).

37. Dorsal exposure of the lachrymal: present (0); absent (1). 76

Texas Tech University, Joshua Sundgren, May 2021

38. Shape of the lachrymal: dorsoventrally short and block shaped (0); dorsoventrally elongate and shaped like an inverted L (1).

39. Orientation of the lachrymal orbital margin: strongly sloping anterodorsally (0); erect and close to vertical (1).

40. Length of the anterior ramus of the lachrymal: greater than half the length of the ventral ramus (0); less than half the length of the ventral ramus (1); absent altogether (2). Ordered.

41. Web of bone spanning junction between anterior and ventral rami of lachrymal: absent and antorbital fossa laterally exposed (0); present, obscuring posterodorsal corner of antorbital fossa (1).

42. Extension of the antorbital fossa onto the ventral end of the lachrymal: present (0); absent (1).

43. Length of the posterior process of the prefrontal: short (0); elongated, so that total prefrontal length is equal to the anteroposterior diameter of the orbit (1).

44. Ventral process of prefrontal extending down the posteromedial side of the lachrymal: present (0); absent (1).

45. Maximum transverse width of the prefrontal: less than 0.25 of the skull width at that level (0); more than 0.25 of the skull width at that level (1).

46. Shape of the orbit: subcircular (0); ventrally constricted making the orbit subtriangular (1).

47. Slender anterior process of the frontal intruding between the prefrontal and the nasal: absent (0); present (1).

48. Jugal-lachrymal relationship: lachrymal overlapping lateral surface of jugal or abutting it dorsally (0); jugal overlapping lachrymal laterally (1).

49. Shape of the suborbital region of the jugal: an anteroposteriorly elongate bar (0); an anteroposteriorly shortened plate (1).

50. Jugal contribution to the antorbital fenestra: absent (0); present (1). 77

Texas Tech University, Joshua Sundgren, May 2021

51. Dorsal process of the anterior jugal: present (0); absent (1).

52. Ratio of the minimum depth of the jugal below the orbit to the distance between the anterior end of the jugal and the anteroventral corner of the infratemporal fenestra: less than 0.2 (0); greater than 0.2 (1).

53. Transverse width of the ventral ramus of the postorbital: less than its anteroposterior width at midshaft (0); greater than its anteroposterior width at midshaft (1).

54. Shape of the dorsal margin of postorbital in lateral view: straight to gently curved (0); with a distinct embayment between the anterior and posterior dorsal processes (1).

55. Height of the postorbital rim of the orbit: flush with the posterior lateral process of the postorbital (0); raised so that it projects laterally to the posterior dorsal process (1).

56. Postfrontal bone: present (0); absent (1).

57. Position of the anterior margin of the infratemporal fenestra: behind the orbit (0); extends under the rear half of the orbit (1); extends as far forward as the midlength of the orbit (2). Ordered.

58. Frontal contribution to the supratemporal fenestra: present (0); absent (1).

59. Orientation of the long axis of the supratemporal fenestra: longitudinal (0); transverse (1).

60. Medial margin of supratemporal fossa: simple smooth curve (0); with a projection at the frontal/postorbital-parietal suture producing a scalloped margin (1).

61. Length of the quadratojugal ramus of the squamosal relative to the width at its base: less than four times its width (0); greater than four times its width (1).

62. Proportion of infratemporal fenestra bordered by squamosal: more than 0.5 of the depth of the infratemporal fenestra (0); less than 0.5 of the depth of the infratemporal fenestra (1).

63. Squamosal-quadratojugal contact: present (0); absent (1).

Texas Tech University, Joshua Sundgren, May 2021

64. Angle of divergence between jugal and squamosal rami of quadratojugal: close to 90 degrees (0); close to parallel (1).

65. Length of jugal ramus of quadratojugal: no longer than the squamosal ramus (0); longer than the squamosal ramus (1).

66. Shape of the rostral end of the jugal ramus of the quadratojugal: tapered (0); dorsoventrally expanded (1).

67. Relationship of quadratojugal to jugal: jugal overlaps the lateral surface of the quadratojugal (0); quadratojugal overlaps the lateral surface of the jugal (1); quadratojugal sutures along the ventrolateral margin of the jugal (2).

68. Position of the quadrate foramen: on the quadrate-quadratojugal suture (0); deeply incised into, and partly encircled by, the quadrate (1); on the quadrate-squamosal suture, just below the quadrate head (2).

69. Shape of posterolateral margin of quadrate: sloping anterolaterally from posteromedial ridge (0); everted posteriorly creating a posteriorly facing fossa (1); posterior fossa deeply excavated, invading quadrate body (2). Ordered.

70. Exposure of the lateral surface of the quadrate head: absent, covered by lateral sheet of the squamosal (0); present (1).

71. Proportion of the length of the quadrate that is occupied by the pterygoid wing: at least 70 per cent (0); greater than 70 per cent (1).

72. Depth of the occipital wing of the parietal: less than 1.5 times the depth of the foramen magnum (0); more than 1.5 times the depth of the foramen magnum (1).

73. Position of foramina for mid-cerebral vein on occiput: between supraoccipital and parietal (0); on the supraoccipital (1).

74. Postparietal fenestra between supraoccipital and parietals: absent (0); present (1).

75. Shape of the supraoccipital: diamond-shaped, at least as high as wide (0); semilunate and wider than high (1).

Texas Tech University, Joshua Sundgren, May 2021

76. Orientation of the supraoccipital plate: erect to gently sloping (0); strongly sloping forward so that the dorsal tip lies level with the basipterygoid processes (1).

77. Orientation of the paroccipital processes in occipital view: slightly dorsolaterally directed to horizontal (0); ventrolaterally directed (1).

78. Orientation of the paroccipital processes in dorsal view: posterolateral forming a V- shaped occiput (0); lateral forming a flat occiput (1)

79. Size of the post-temporal fenestra: large fenestra (0); a small hole that is much less than half the depth of the paroccipital process (1).

80. Exit of the mid-cerebral vein: through trigeminal foramen (0); through a separate foramen anterodorsal to trigeminal foramen (1).

81. Shape of the floor of the braincase in lateral view: relatively straight with the basal tuberae, basipterygoid processes and parasphenoid rostrum roughly aligned (0); bent with the basipterygoid processes and the parasphenoid rostrum below the level of the basioccipital condyle and the basal tuberae (1); bent with the basal tuberae lowered below the level of the basioccipital and the parasphenoid rostrum raised above it (2).

82. Shape of basal tuberae: knob-like, with basisphenoidal component rostral to basioccipital component (0); forming a transverse ridge with the basisphenoidal component lateral to the basioccipital component (1).

83. Length of the basipterygoid processes (from the top of the parasphenoid to the tip of the process): less than the height of the braincase (from the top of the parasphenoid to the top of the supraoccipital) (0); greater than the height of the braincase (from the top of the parasphenoid to the top of the supraoccipital) (1).

84. Ridge formed along the junction of the parabasisphenoid and the basioccipital, between the basal tuberae: present with a smooth anterior face (0); present with a median fossa on the anterior face (1); absent with the basal tuberae being separated by a deep posteriorly opening U-shaped fossa (2).

85. Deep septum spanning the interbasipterygoid space: absent (0); present (1).

Texas Tech University, Joshua Sundgren, May 2021

86. Dorsoventral depth of the parasphenoid rostrum: much less than the transverse width (0); about equal to the transverse width (1).

87. Shape of jugal process of ectopterygoid: gently curved (0); strongly recurved and hook- like (1).

88. Pneumatic fossa on the ventral surface of the ectopterygoid: present (0); absent (1).

89. Relationship of the ectopterygoid to the pterygoid: ectopterygoid overlapping the ventral surface of the pterygoid (0); ectopterygoid overlapping the dorsal surface of the pterygoid (1).

90. Position of the maxillary articular surface of the palatine: along the lateral margin of the bone (0); at the end of a narrow anterolateral process due to the absence of the posterolateral process (1).

91. Centrally located tubercle on the ventral surface of palatine: absent (0); present (1).

92. Medial process of the pterygoid forming a hook around the basipterygoid process: absent (0); flat and blunt-ended (1); bent upward and pointed (2). Ordered.

93. Length of the vomers: less than 0.25 of the total skull length (0); more than 0.25 of the total skull length (1).

94. Position of jaw joint: no lower than the level of the dorsal margin of the dentary (0); depressed, well below this level (1).

95. Shape of upper jaws in ventral view: narrow with an acute rostral apex (0); broad and U- shaped (1).

96. Length of the external mandibular fenestra: more than 0.1 of the length of the mandible (0); less than 0.1 of the length of the mandible (1).

97. Caudal end of dentary tooth row medially inset with a thick lateral ridge on the dentary forming a buccal emargination: absent (0); present (1).

98. Height: length ratio of the dentary: less than 0.2; greater than 0.2 (1).

Texas Tech University, Joshua Sundgren, May 2021

99. Orientation of the symphyseal end of the dentary: in line with the long axis of the dentary (0); strongly curved ventrally (1).

100. Position of first dentary tooth: adjacent to symphysis (0); inset one tooth's width from the symphysis (1).

101. Dorsoventral expansion at the symphyseal end of the dentary: absent (0); present (1).

102. Splenial foramen: absent (0); present and enclosed (1); present and open anteriorly (2). Ordered.

103. Splenial-angular joint: flattened sutured contact (0); synovial joint surface between tongue-like process of angular fitting in groove of the splenial (1).

104. A stout, triangular, medial process of the articular, behind the glenoid: present (0); absent (1).

105. Length of the retroarticular process: less than the depth of the mandible below the glenoid (0); greater than the depth of the mandible below the glenoid (2).

106. Strong medial embayment behind glenoid of the articular in dorsal view: absent (0); present (1).

107. Number of premaxillary teeth: four (0); more than four (1).

108. Number of dentary teeth (in adults): less than 18 (0); 18 or more (1).

109. Arrangement of teeth within the jaws: linearly placed, crowns not overlapping (0); imbricated with distal side of tooth overlapping mesial side of the succeeding tooth (1).

110. Orientation of the maxillary tooth crowns: erect (0); procumbent (1).

111. Orientation of the dentary tooth crowns: erect (0); procumbent (1).

112. Teeth with basally constricted crowns: absent (0); present (1). 113. Tooth-tooth occlusal wear facets: absent (0); present (1).

Texas Tech University, Joshua Sundgren, May 2021

114. Mesial and distal serrations of the teeth: fine and set at right angles to the margin of the tooth (0); coarse and angled upwards at an angle of 45 degrees to the margin of the tooth (1).

115. Distribution of serrations on the maxillary and dentary teeth: present on both the mesial and distal carinae (0); absent on the posterior carinae (1); absent on both carinae (2).

116. Long axis of the tooth crowns distally recurved: present (0); absent (1).

117. Texture of the enamel surface: entirely smooth (0); finely wrinkled in some patches (1); extensively and coarsely wrinkled (2). Ordered.

118. Lingual concavities of the teeth: absent (0); present (1). 119. Longitudinal labial grooves on the teeth: absent (0); present (1).

120. Distribution of the serrations along the mesial and distal carinae of the tooth: extend along most of the length of the crown (0); restricted to the upper half of the crown (1).