A considerable number of azhdarchid pterosaur fossils have been recovered from Maastrichtian deposits of North America. Historically, most of these specimens have been referred to Quetzalcoatlus based on a preliminary understanding of the genus. Further study of Quetzalcoatlus and other azhdarchids has increased our understanding of the anatomy and diversity of the clade, and warrants reappraisal of specimens previously referred to this genus. Here we redescribe an azhdarchid cervical vertebra recovered from the Maastrichtian Hell Creek Formation of Montana, U.S.A. Digitization of this specimen via laser scanning allows a more detailed assessment and reconstruction of this specimen's morphology, revealing both unique characters and unique character combinations. We therefore assign this specimen to a new genus and species of medium-sized azhdarchid, Infernodrakon hastacollis gen. et sp. nov. Phylogenetic analysis recovers Infernodrakon as more closely related to Arambourgiania than to Quetzalcoatlus. Review of Maastrichtian azhdarchid material from North America reveals a high diversity despite the relatively fragmentary fossil record for this clade.

Bite marks attributed to adult Tyrannosaurus rexare common in the fossil record and have been subject to numerous studies, though relatively few bite marks attributed to T. rexhave been traced to juveniles. However, a series of recent studies have contributed new information on bite force, behavior, and ecological interactions of juvenile Tyrannosaurus rex, providing insight into ontogenetic changes in lifestyle and ecological roles of juvenile tyrannosaurs in the late Cretaceous of North America. Recent bite force estimates for a juvenile Tyrannosaurus rexwere based on mechanical tests designed to replicate bite marks previously attributed to a T. rex of approximately 13 years old in the centrum of a caudal vertebra of Edmontosaurus(BMR P2007.4.1) and the left maxilla and nasal of a juvenile Tyrannosaurus (BMR P2002.4.1). Results indicate an estimated bite force of 5,641.19 N, and suggest that bite forces were increasing parallel to growth and were utilizing the same prey as adults. Additionally, evidence of intraspecific aggression in the form of lesions resulting from face biting are present in over 50% of juvenile and adult tyrannosaurs. The high frequency of facial scars positively correlates with the inferred onset of sexual maturity. Furthermore, lesions attributed to a Trichomonas gallinae-like parasite are present on the dentaries and surangulars of adult tyrannosaurs. Presented here is the first evidence of similar pathologies on a juvenile Tyrannosaurus rex that also possesses facial scars from intraspecific aggression, supporting a cause-and-effect relationship between the two groups of facial pathologies. Collectively, these findings suggest tyrannosaurs increased interactions, aggressive bouts, and potential transmission of parasites at the onset of sexual maturity as they were moving into different ecological niches. Furthermore, the frequency and category of pathologies in late Cretaceous tyrannosaurs and late Jurassic theropods of North America are compared with the unique guild structures of tyrannosaurs in the late Cretaceous of North America, suggesting a possible relationship between theropod diversity, behavior, and parasitism.

Dental complexes of sauropod dinosaurs have been studied in members of Diplodocoidea and Macronaria. However, the disparity among the number of replacement teeth between the premaxilla, maxilla, and dentary of apatosaurine sauropods has yet to be fully investigated. TATE-099, a nearly complete and associated apatosaurine skull and dental complexes from the upper Morrison Formation (Upper Jurassic) at Como Bluff, Wyoming, contains cranial characters consistent with Apatosaurus sp. Unerupted dental complexes of the right premaxilla, maxilla, and dentary were imaged and digitally reconstructed using computed tomography (CT). Results indicate four premaxillary alveolar positions each with 5???7 unerupted replacement teeth, 10 maxillary alveolar positions each with 3???5 unerupted replacement teeth, and 10 dentary alveolar positions each with only 1???2 unerupted replacement teeth. The capacity of replacement teeth in TATE-099 is higher than reported in the genus Diplodocus and consistent with data from previous studies on niche partitioning among coeval Morrison Formation sauropods. Disparity among the capacity of dental complexes of TATE-099 further suggests novel feeding mechanics in apatosaurines. CT data also support a new hypothesis of tooth replacement in diplodocids, where entire rows of teeth are replaced as a single unit, rather than individually. The high-capacity of replacement teeth in the premaxilla is only known to be succeeded by one taxon (Nigersaurus) and suggests frequent wear of the premaxillary teeth. However, considerably fewer replacement teeth in the dentary of TATE-099 suggests less-frequent. These results offer insight into the feeding mechanisms and disparity of sauropods within Flagellicaudata.

Background Bite marks attributed to adult Tyrannosaurus rex have been subject to numerous studies. However, few bite marks attributed to T. rex have been traced to juveniles, leaving considerable gaps in understanding ontogenetic changes in bite mechanics and force, and the paleoecological role of juvenile tyrannosaurs in the late Cretaceous. Methods Here we present bite force estimates for a juvenile Tyrannosaurus rex based on mechanical tests designed to replicate bite marks previously attributed to a T. rex of approximately 13 years old. A maxillary tooth of the juvenile Tyrannosaurus specimen BMR P2002.4.1 was digitized, replicated in dental grade cobalt chromium alloy, and mounted to an electromechanical testing system. The tooth was then pressed into bovine long bones in various locations with differing cortical bone thicknesses at varying speeds for a total of 17 trials. Forces required to replicate punctures were recorded and puncture dimensions were measured. Results Our experimentally derived linear models suggest bite forces up to 5,641.19 N from cortical bone thickness estimated from puncture marks on an Edmontosaurus and a juvenile Tyrannosaurus. These findings are slightly higher than previously estimated bite forces for a juvenile Tyrannosaurus rex of approximately the same size as BMR P2002.4.1 but fall within the expected range when compared to estimates of adult T. rex. Discussion The results of this study offer further insight into the role of juvenile tyrannosaurs in late Cretaceous ecosystems. Furthermore, we discuss the implications for feeding mechanisms, feeding behaviors, and ontogenetic niche partitioning.

Theropod dinosaur feeding traces and tooth marks yield paleobiological and paleoecological implications for social interactions, feeding behaviors, and direct evidence of cannibalism and attempted predation. However, ascertaining the taxonomic origin of a tooth mark is largely dependent on both the known regional biostratigraphy and the ontogenetic stage of the taxon. Currently, most recorded theropod feeding traces and bite marks are attributed to adult theropods, whereas juvenile and subadult tooth marks have been rarely reported in the literature. Here we describe feeding traces attributable to a late-stage juvenile Tyrannosaurus rex on a caudal vertebra of a hadrosaurid dinosaur. The dimensions and spacing of the traces were compared to the dentition of Tyrannosaurus rex maxillae and dentaries of different ontogenetic stages. These comparisons reveal that the tooth marks present on the vertebra closely match the maxillary teeth of a late-stage juvenile Tyrannosaurus rex specimen histologically determined to be 11-12 years of age. These results demonstrate that late-stage juvenile and subadult tyrannosaurs were already utilizing the same large-bodied food sources as adults despite lacking the bone-crushing abilities of adults. Further identification of tyrannosaur feeding traces coupled with experimental studies of the biomechanics of tyrannosaur bite forces from younger ontogenetic stages may reveal dynamic dietary trends and ecological roles of Tyrannosaurus rex throughout ontogeny.

In 2001, a nearly complete sub-adult Tenontosaurus tilletti was collected from the Antlers Formation (Aptian-Albian) of southeastern Oklahoma. Beyond its exceptional preservation, computed tomography (CT) and physical examination revealed this specimen has five pathological elements with four of the pathologies a result of trauma. Left pedal phalanx I-1 and left dorsal rib 10 are both fractured with extensive callus formation in the later stages of healing. Left dorsal rib 7 (L7) and right dorsal rib 10 (R10) exhibit impacted fractures compressed 26 mm and 24 mm, respectively. The fracture morphologies in L7 and R10 indicate this animal suffered a strong compressive force coincident with the long axis of the ribs. All three rib pathologies and the pathological left phalanx I-1 are consistent with injuries sustained in a fall. However, it is clear from the healing exhibited by these fractures that this individual survived the fall. In addition to traumatic fractures, left dorsal rib 10 and possibly left phalanx I-1 have a morphology consistent with post-traumatic infection in the form of osteomyelitis. The CT scans of left metacarpal IV revealed the presence of an abscess within the medullary cavity consistent with a subacute form of hematogenous osteomyelitis termed a Brodie abscess. This is only the second reported Brodie abscess in non-avian dinosaurs and the first documented occurrence in herbivorous dinosaurs. The presence of a Brodie abscess, known only in mammalian pathological literature, suggest mammalian descriptors for bone infection may be applicable to non-avian dinosaurs.

Bone distribution data are essential for taphonomic assessments of bonebeds. The Cleveland-Lloyd Dinosaur Quarry (CLDQ), an Allosaurus-dominated bonebed within the Upper Jurassic Morrison Formation, has been researched for nearly 100 years, but published maps are scarce considering the impor¬tance and density of the assemblage. Additionally, few detailed maps of bones from the CLDQ have been published in two dimensions, whereas the third, the stratigraphic/vertical, dimension has never been recorded. Utilizing standard field mapping techniques as well as photogrammetry, the three-dimensional orientations of bones currently exposed in the quarry have been analyzed for potential dispersal patterns. Additionally, a “living” or continuously updatable, photogrammetric map which allows for researchers to view the bones in three dimensions throughout the course of excavation has been created. Continued photogrammetry in future field seasons will allow visualization of bones in three dimensions even after the currently exposed bones have been removed. Utilizing these newly available data, two distinct clusters of bone within the South Butler Building at the quarry are identified. Based on statistically significant average orientations and depths of these bones, early-stage post-mortem transport of carcasses prior to disarticulation (i.e., bloat and float) is supported as an important transport and depositional process within the quarry assemblage. Furthermore, possible evidence of multiple depositional events is discussed.

The Mygatt-Moore Quarry is a deposit of several thousand dinosaur bones in the Brushy Basin Member of the Morrison Formation in western Colorado. The site has been worked for more than 30 years and nearly 2400 mapped specimens have been collected. This study gathered data about the quarry from many sources to investigate the origin of the deposit. The Mygatt-Moore Quarry appears to be an attritional deposit of a relatively restricted diversity of dinosaurs, with few other non-dinosaurian taxa, that accumulated in a vernal pool deposit in an overbank setting. Bone modification was mostly by corrosion and breakage by trampling; scavenging was abundant. The paleofauna is dominated by Allosaurus and Apatosaurus (MNI and NIS), with the polacanthid ankylosaur Mymoorapelta less common. The matrix of the main quarry layer includes abundant carbonized fragments of plant material, and the mud during the time of deposition may have been often at least damp and occasionally acidic and dysoxic. The Cleveland-Lloyd Dinosaur Quarry is a close correlate of the Mygatt-Moore Quarry in terms of lithology and taphonomy, but demonstrates significant differences upon close inspection of matrix details and bone modification. Large quarries of fine-grained facies in the Morrison Formation possess a very different preservation mode as well as different taxon and relative abundance profiles from those in coarser sediments, which suggests that more may be learned in the future from taphofacies study of large quarries in mudstone beds.

The Cleveland-Lloyd Dinosaur Quarry (CLDQ) is the densest deposit of Jurassic theropod dinosaurs discovered to date. Unlike typical Jurassic bone deposits, it is dominated by the presence of Allosaurus fragilis. Since excavation began in the 1920s, numerous hypotheses have been put forward to explain the taphonomy of CLDQ, including a predator trap, a drought assemblage, and a poison spring. In an effort to reconcile the various interpretations of the quarry and reach a consensus on the depositional history of CLDQ, new data is required to develop a robust taphonomic framework congruent with all available data. Here we present two new data sets that aid in the development of such a robust taphonomic framework for CLDQ. First, x-ray fluorescence of CLDQ sediments indicate elevated barite and sulfide minerals relative to other sediments from the Morrison Formation in the region, suggesting an ephemeral environment dominated by periods of hypereutrophic conditions during bone accumulation. Second, the degree of abrasion and hydraulic equivalency of small bone fragments dispersed throughout the matrix were analyzed from CLDQ. Results of these analyses suggest that bone fragments are autochthonous or parautochthonous and are derived from bones deposited in the assemblage rather than transported. The variability in abrasion exhibited by the fragments is most parsimoniously explained by local periodic re-working and re-deposition during seasonal fluctuations throughout the duration of the quarry assemblage. Collectively, these data support previous interpretations that the CLDQ represents an attritional assemblage in a poorly-drained overbank deposit where vertebrate remains were introduced post-mortem to an ephemeral pond during flood conditions. Furthermore, while the elevated heavy metals detected at the Cleveland-Lloyd Dinosaur Quarry are not likely the primary driver for the accumulation of carcasses, they are likely the result of multiple sources; some metals may be derived from post-depositional and diagenetic processes, and others are potentially produced from an abundance of decomposing vertebrate carcasses. These new data help to support the inferred depositional environment of the quarry as an ephemeral pond, and represent a significant step in understanding the taphonomy of the bonebed and Late Jurassic paleoecology in this region.

This study explores where and to what degree information is lost in the digitization and additive manufacturing reproduction of fossil specimens to asses the reliablity of these technologies in paleontology research.

Microscopic soft tissues have been identified in fossil vertebrate remains collected from various lithologies. However, the diagenetic mechanisms to preserve such tissues have remained elusive. While previous studies have described infiltration of biofilms in Haversian and Volkmann's canals, biostratinomic alteration (e.g., trampling), and iron derived from hemoglobin as playing roles in the preservation processes, the influence of sediment texture has not previously been investigated. This study uses a Kolmogorov Smirnov Goodness-of-Fit test to explore the influence of biostratinomic variability and burial media against the infiltration of biofilms in bone samples. Controlled columns of sediment with bone samples were used to simulate burial and subsequent groundwater flow. Sediments used in this study include clay-, silt-, and sand-sized particles modeled after various fluvial facies commonly associated with fossil vertebrates. Extant limb bone samples obtained from Gallus gallus domesticus (Domestic Chicken) buried in clay-rich sediment exhibit heavy biofilm infiltration, while bones buried in sands and silts exhibit moderate levels. Crushed bones exhibit significantly lower biofilm infiltration than whole bone samples. Strong interactions between biostratinomic alteration and sediment size are also identified with respect to biofilm development. Sediments modeling crevasse splay deposits exhibit considerable variability; whole-bone crevasse splay samples exhibit higher frequencies of high-level biofilm infiltration, and crushed-bone samples in modeled crevasse splay deposits display relatively high frequencies of low-level biofilm infiltration. These results suggest that sediment size, depositional setting, and biostratinomic condition play key roles in biofilm infiltration in vertebrate remains, and may influence soft tissue preservation in fossil vertebrates.

© 2018 Utah Geological Association. All rights reserved. For permission to copy and distribute, see the following page or visit the UGA website at www.utahgeology.org for information. Email inquiries to GIW@utahgeology.org. PALEONTOLOGY, TAPHONOMY, AND SEDIMENTOLOGY OF THE MYGATT-MOORE QUARRY, A LARGE DINOSAUR BONEBED IN THE MORRISON FORMATION, WESTERN COLORADO—IMPLICATIONS FOR UPPER JURASSIC DINOSAUR PRESERVATION MODES

A cervical vertebra preserved at the famous and productive Cleveland-Lloyd Dinosaur Quarry in the Upper Jurassic Morrison Formation of Utah is that of an Apatosaurus, a sauropod dinosaur genus not previously recognized at the site and the first new dinosaur taxon identified at the site in years. The presence of Apatosaurus at a mudstone site dominated by other taxa, both theropod and sauropod, suggests a pattern of preservation within the Morrison Formation in which sites in fine-grained sediments yield dramatically uneven relative abundances of dinosaurs, with variable dominant taxa by site, compared with more time-averaged and attritional coarse-grained channel sandstone deposits. In addition, the continued demonstration of the wide-spread occurrence and abundance of Apatosaurus within the Morrison Formation, and the absence of its clade among diplodocid faunas on other continents, suggest that this group may have been endemic to North America during the Late Jurassic and that it may have originated there, though this is far from clear.

The Morrison Formation contains a number of large quarries that have yielded dinosaurs and other vertebrates, and many of these occur in sandstone beds representing ancient river channels. However, a number of very productive sites occur in mudstone beds representing other environments such as ephemeral ponds, and some of these yield both large dinosaurs and microvertebrates; these localities in mudstone beds represent different taphonomic modes of preservation and often preserve vertebrate taxa in different relative abundances from the channel sandstone sites. Among these important and very productive mudstone localities are the Cleveland-Lloyd Quarry, the Mygatt-Moore Quarry, and the microvertebrate sites of the Fruita Paleontological Area, and each of these preserves distinct vertebrate paleofaunas, different from sandstone sites and from each other, suggesting that mudstone localities had a very different mode of sampling the local biotas than did sites in sandstone.