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Abstract Despite documented ecomorphological shifts toward an herbivorous diet in several coelurosaurian lineages, the evolutionary tempo and mode of these changes remain poorly understood, hampered by sparse cranial materials for early representatives of major clades. This is particularly true for Therizinosauria, with representative crania best known for the late‐divergingErlikosaurus andrewsiand the early taxonJianchangosaurus yixianensis. Here we describe a series of new cranial bones ofFalcarius utahensis, the geologically oldest therizinosaurian from the Early Cretaceous Cedar Mountain Formation, Utah, United States. This new material provides the most complete understanding of the skull to date forFalcariusand frames the pattern and timing of cranial evolution in therizinosaurians and early coelurosaurians. Previously unknown elements include a well‐preserved maxilla, jugal, parietals, squamosal, laterosphenoids, and pterygoid. Computed tomography data differentiate the incisiform rostral dentary dentition from possible premaxillary teeth, the first in a therizinosaurian. Notable features include a primitive morphology of the jugal and frontoparietal complex shared with other early diverging taxa (e.g., tyrannosauroids,Incisivosaurus,Ornitholestes, Fukuivenator), and a large maxillary fenestra, convergent with troodontids. Additional specimens of previously known elements confirm their taxonomic utility and provide insight into intraspecific variation. Following patterns of other archosaurs, variable traits relate to the prominence of ridges and contours (likely associated with musculature) and the proportions of pneumatic features, whereas invariant traits correspond to the topology of bony contacts and major cranial nerves. Early, integrated evolution of the rostrum and adductor complex characterized early therizinosaurians, which was further modified alongside reduced paranasal complexity in later therizinosaurids. 

ABSTRACT The external surfaces of non‐avian dinosaur eggs are not usually smooth like those of their avian descendants. Unique ornamentation patterns sculpt the exterior of the eggs, a trait that is difficult to interpret because of its scarcity in modern taxa. One avian species that does homoplastically present similar external eggshell ornamentation to that of non‐avian dinosaurs isDromaius novaehollandiaeLatham, 1790, the emu. Here we useD. novaehollandiaeeggs in conjunction with a clutch of oviraptorosaurian dinosaur eggs (NCSM 33576,Macroelongatoolithus carlylei) to test new methods of quantifying external eggshell ornamentation. Currently, the only scientific language for describing and comparing ornamentation styles in fossil ootaxa is restricted to qualitative categorization, which introduces issues of subjectivity and overly broad and overlapping typification. In this study, we derived and tested a new statistical quantitative approach to quantifying ornamentation that includes two existing functions of the molaR package in R previously applied to shape quantifications of fossil teeth, and ‘Orientation’, a novel function presented as a proxy for ‘direction’, needed to capture directionality. Results demonstrate that (1) the quantitative approach provides statistical backing to gross qualitative observations; (2) statistically significant differences exist between the ornamentation inD. novaehollandiaeandM. carlylei, particularly in terms of relief; (3) intranest variation ofM. carlyleican be demonstrated from harmonic meanp‐value differences between different pairs of eggs. This method offers a strong platform to consolidate quantitative measures with existing qualitative categories, improve the diagnoses of ootaxa and answer broad ecological and evolutionary questions regarding dinosaur reproduction. Moreover, wider application of the technique is encouraged for a multi‐proxy quantitative analysis of any paleontological surfaces, such as echinoderm tests, geological ripple marks or dentition. 

ABSTRACT Current investigations into the Albian–Cenomanian sedimentary record within the Western Interior have identified multiple complex tectono‐sedimentary process–response systems during the ongoing evolution of North America. One key sedimentary succession, the upper Cedar Mountain Formation (Short Canyon Member and Mussentuchit Member), has historically been linked to various regionally and continentally significant tectonic events, including Sevier fold‐and‐thrust deformation. However, the linkage between the Short Canyon Member and active Sevier tectonism has been unclear due to a lack of high‐precision age constraints. To establish temporal context, this study compares maximum depositional ages from detrital zircons recovered from the Short Canyon Member with that of a modified Bayesian age stratigraphic model (top‐down) to infer that the Short Canyon Member was deposited atca100 Ma, penecontemporaneous with rejuvenated thrusting across Utah [Pavant (Pahvant), Iron Springs and Nebo thrusts]. These also indicate a short depositional hiatus with the lowermost portion of the overlying Mussentuchit Member. The Short Canyon Member and Mussentuchit Member preserve markedly different sedimentary successions, with the Short Canyon Member interpreted to be composed of para‐autochthonous orogen–transverse (across the Sevier highlands) clastics deposited within a series of stacked distributive fluvial fans. Meanwhile, the muddy paralic Mussentuchit Member was a mix of orogen–transverse (Sevier highlands and Cordilleran Arc) and orogen–parallel basinal sediments and suspension settling fines within the developing collisional foredeep. However, the informally named last chance sandstone (middle sandstone of the Mussentuchit Member) is identified as an orogen–transverse sandy debris flow originating from the Sevier highlands, similar to the underlying Short Canyon Member. During this phase of landscape evolution, the Short Canyon Member – Mussentuchit Member depocentre was a sedimentary conduit system that would fertilize the Western Interior Seaway with ash‐rich sediments. These volcaniclastic contributions, along with penecontemporaneous deposits across the western coastal margin of the Western Interior Seaway, eventually would have lowered oxygen content and resulted in a contributing antecedent trigger for the Cenomanian–Turonian transition Oceanic Anoxic Event 2. 

Abstract Paleopathological diagnoses provide key information on the macroevolutionary origin of disease as well as behavioral and physiological inferences that are inaccessible via direct observation of extinct organisms. Here we describe the external gross morphology and internal architecture of a pathologic right second metatarsal (MMNS VP‐6332) of a large‐bodied ornithomimid (~432 kg) from the Santonian (Upper Cretaceous) Eutaw Formation in Mississippi, using a combination of X‐ray computed microtomography (microCT) and petrographic histological analyses. X‐ray microCT imaging and histopathologic features are consistent with multiple complete, oblique to comminuted, minimally displaced mid‐diaphyseal cortical fractures that produce a “butterfly” fragment fracture pattern, and secondary osteomyelitis with a bone fistula formation. We interpret this as evidence of blunt force trauma to the foot that could have resulted from intra‐ or interspecific competition or predator–prey interaction, and probably impaired the function of the metatarsal as a weight‐bearing element until the animal's death. Of particular interest is the apparent decoupling of endosteal and periosteal pathological bone deposition in MMNS VP‐6332, which produces transverse sections exhibiting homogenously thick endosteal pathological bone in the absence of localized periosteal reactive bone. These distribution and depositional patterns are used as criteria for ruling out a pathological origin in favor of a reproductive one for unusual endosteal bone in fossil specimens. On the basis of MMNS VP‐6332, we suggest caution in their use to substantiate a medullary bone identification in extinct archosaurians. 

On September 18, 1996, Grand Staircase-Escalante National Monument (GSENM) became the first national monument managed by the US Bureau of Land Management (BLM) and one of the first to protect a landscape based partly on its opportunity for scientific discovery. Its creation was a watershed moment in public land management, because to meet the mandates for its first monument, BLM opted to implement unprecedented support of resource investigations for numerous natural and cultural sciences, including establishing its first ever in-house paleontological field program. The rationale for this was taken directly from the establishing presidential proclamation (6920) which called out GSENM’s untapped paleontological treasure trove as “world-class.” The proclamation also singled out the Late Cretaceous vertebrate fossil record of the Kaiparowits Plateau, largely known at the time through the pioneering work of Drs. Jeff Eaton and Rich Cifelli, who had spent years teasing out the mammalian evolutionary story preserved within. Their work on Mesozoic mammals, alongside sporadic work by other institutions (mainly the University of Utah and Brigham Young University) in the 1970s and 1980s, demonstrated that the Kaiparowits Plateau also held a substantial macrovertebrate record that included beautifully preserved dinosaur skeletons. However, a lack of coordinated effort and the difficult nature of fieldwork in the rugged badlands led to what can only be described as desultory results. The leverage that came with monument status, including logistical and financial support provided by BLM, made this resource more accessible to the paleontological community, stimulating a sudden burst of new field research and discovery. Initial, coordinated, and collaborative fossil inventories started in 2000 by joint BLM, Utah Museum of Natural History, Museum of Northern Arizona, and Utah Geological Survey teams led to a cascade of discoveries, including sites preserving plants, invertebrates, trace fossils, microvertebrates, and macrovertebrates, contextualized by new geological insights. Many of these new fossil finds represent species entirely new to science, with some sites preserving intact snapshots of Late Cretaceous ecosystems that are unmatched globally. Unique geologic conditions resulted in spectacular preservation, sometimes even including soft tissue traces. This renaissance in North American Late Cretaceous paleontology would not have been possible without the focused resources and effort facilitated by the creation of GSENM and the subsequent prioritization of inventory and basic research in its mission. In addition to the science, the public benefits of these efforts have been immense, providing opportunities for direct involvement in the scientific process through volunteer programs, training for several generations of future paleontologists and geologists, innumerable educational programs, and exposure in national and international media outlets through articles, television, and interviews. The collaborative and far-reaching paleontological effort at GSENM has highlighted an often overlooked aspect of public lands management: the importance of US public lands for scientific discovery and education. 

Abstract Increased use and improved methodology of carbonate clumped isotope thermometry has greatly enhanced our ability to interrogate a suite of Earth‐system processes. However, interlaboratory discrepancies in quantifying carbonate clumped isotope (Δ₄₇) measurements persist, and their specific sources remain unclear. To address interlaboratory differences, we first provide consensus values from the clumped isotope community for four carbonate standards relative to heated and equilibrated gases with 1,819 individual analyses from 10 laboratories. Then we analyzed the four carbonate standards along with three additional standards, spanning a broad range of δ⁴⁷and Δ₄₇values, for a total of 5,329 analyses on 25 individual mass spectrometers from 22 different laboratories. Treating three of the materials as known standards and the other four as unknowns, we find that the use of carbonate reference materials is a robust method for standardization that yields interlaboratory discrepancies entirely consistent with intralaboratory analytical uncertainties. Carbonate reference materials, along with measurement and data processing practices described herein, provide the carbonate clumped isotope community with a robust approach to achieve interlaboratory agreement as we continue to use and improve this powerful geochemical tool. We propose that carbonate clumped isotope data normalized to the carbonate reference materials described in this publication should be reported as Δ₄₇(I‐CDES) values for Intercarb‐Carbon Dioxide Equilibrium Scale. 

The first fossil eggshell from the Cenomanian-age Mussentuchit Member of the Cedar Mountain Formation was described over fifty years ago. In the half-century since, oodiversity of this rock unit has been limited to a single, taxonomically unstable ootaxon, currently formulated asMacroelongatoolithus carlylei. Recently, there has been a renewed effort to recover and describe the macrofauna of the Mussentuchit; however, these advances are limited to the body fossil record. Here, we examine the range of eggshells present in the Mussentuchit Member and assess the preserved biodiversity they represent. Gross morphological and microstructural inspection reveals a greater diversity of eggshells than previously described. We identify six ootaxa: three Elongatoolithidae oogenera (Macroelongatoolithus,Undulatoolithus,Continuoolithus), eggs laid by oviraptorosaur dinosaurs; two oospecies ofSpheroolithuslaid by ornithopod dinosaurs; andMycomorphoolithus kohringi, laid by a crocodylomorph. The diversity of Elongatoolithidae in the Mussentuchit requires a co-occurrence of at least three putative oviraptorosaurs, the oldest such phenomenon in North America. The occurrence of the crocodylomorph oogenusMycomorphoolithusis the first recognized occurrence outside of Europe, and the youngest yet documented. This new ooassemblage is more representative of the known paleobiodiversity of Cenomanian-age strata of Western North America and complements the body fossil record in improving our understanding of this crucial—yet poorly documented—timeslice within the broader evolution of the Cretaceous Western Interior Basin. 

Understanding the effects of climatic upheavals during the Early to Late Cretaceous transition is essential for characterizing the tempo of tectonically driven landscape modification and biological interchange; yet, current chronostratigraphic frameworks are too imprecise, even on regional scales, to address many outstanding questions. This includes the Mussentuchit Member of the uppermost Cedar Mountain Formation, central Utah (southwestern United States), which could provide crucial insights into these impacts within the Western Interior Basin of North America yet remains imprecisely constrained. Here, we present high-precision U-Pb zircon dates from four primary ash beds distributed across ~50 km in central Utah that better constrain the timing of deposition of the Mussentuchit Member and the age of entombed fossils. Ages for ash beds are interpreted through a combination of Bayesian depositional age estimation and stratigraphic age modeling, resulting in posterior ages from 99.490 + 0.057/–0.050 to 98.905 + 0.158/–0.183 Ma. The age model predicts probabilistic ages for fossil localities between the ashes, including new ages for Moros intrepidus, Siats meekerorum, and several undescribed ornithischian dinosaur species of key interest for understanding the timing of faunal turnover in western North America. This new geochronology for the Mussentuchit Member offers unprecedented temporal insights into a volatile interval in Earth’s history.